Geological Fieldworkcontinues with the Two- Sectionformat Adopted in the Last Volume (Geologicalbranch Paper 1982-1 1

Home , Mist Mountain Formation, Mount Richards

GeologicalFieldwork 1952 a summary of field activities of the geological branch, mineral resources division Paper 1983- 1

RavinceofBritishcolwnbia Ministry of Energy, Mines and Petroleum Resources ISSN 0381-243s

Victoria British Columbia Canada

May 1983 FOREWORD

This is theninth year of publication of Geological Field- work, a publicationdesigned acquaintto theinterested publicwith thepreliminary results of fieldworkof tire GeologicalBranch as soon as possibleafter the field season. The reports are writtenwithout the benefit of extensive laboratory or officestudies. To improve the qualityof presentation,figures in this year's publication were doneby our draughtingsection.

Thisedition of Geological Fieldworkcontinues with the two- sectionformat adopted in the last volume (GeologicalBranch Paper 1982-1 1. The Project and AppliedGeology sectic'n includesreports of metallic and coalfieldinvestigations, reports of District Geologists, andproperty examinations related to some mineral properties funded inpart by Ministry programs. The OtherInvestigations section consists mainly of reports of work doneby different universities in

The coverphotograph depicts geologists examining tha discovery outcrops at Granduc.

Outputof this publication was coordinatedby A. Panteleyev and W. J. WMillan.Manuscript input was by D. I3ulinckxof GeoscienceProjects. Draughting of the figures in the Project andApplied Geology section of the report was by El. HOensen, P. Chicorelli, and J. Armitage of the draughtingoffice and Ian Webster of GeoscienceProjects.

A. Sutherland Brown, ChiefGeologist, GeologicalBranch, MineralResources Division.

3 "_

DISTRIBUTION OF PROGRAMS 1982 GEOLOGICAL FIELDWORK

MINISTRY UNIVERSITYPROJECTS- 0 GENERALREPORTS-24,25

Figure 1. Distribution of program. Geological Fleldwork, 1982

4 TABLE OF COBTEBTS

PROJECT AND AF'PLIED GEOLOGY Page 1 ~oy,T.: Geology inthe Vicinity of theSullivan Deposit, Kimberley,British Columbia(82F, G) ...... 9

2 Addie, G. G.: 'A-1' BluebirdAdit, An Example Of Galena- coatedJoints rather thanVeins (82F/14) ...... 18

3 Grieve, D. A. and Fraser,Janine M.: LineCreek and Crown Mountain Areas,Elk Valley Coalfield (82G/10, 15) ...... 21

4 Church, B. N. andRobertson, S.: Geologyand Magnetometer Survey of the SapphoGold-Silver-Platinum-Copper Prospect(82E/2) ...... 27

5 Church, B. N. andSuesser, U.: Geologyand Magnetostrati- graphy of Miocene Basalts of the Okanagan Highlands, British Columhia(82L/2, 31 ...... 33

6 Eastwood, G.E.P.: LeechRiver Area, Vancouver Islan,3 (92B/5,12) ...... 37 SickerProject (92B/13) ...... 46

7 Church, B. N. and Brasnett, D.: Geologyand GravitySurvey of thenllameen Coal Basin(92H) ...... 47

8 Ray, G. E.: TheNagy Gold Ocurrences,Doctors Point,, Harrison Lake (92H/12W) ...... 55

9 Ray, G. E.: Carolin Mine - Coquihalla Gold Belt Pro:ject (92H/6, 11) ...... 63

10 White, G. V.: The Bluesky - A Stratigraphic Marker 1.n NortheasternBritish Columbia(931. 0, P) .....,...... 85

11 Church, B. N. andEvans, S. G.: Basalts Of the Kamloops Group in Salmon River Area (82L/5) ...... 89

12 Legun, A.: Stratigraphy and SedimentologyNotes on the BullheadMountain-Peace River Canyon, CarbonCreek Area, NortheasternBritish Columbia(930/15, 16; 94B/1, 2) ...... 93

13 Alldrick, D. J.: The MosquitoCreek Mine, Caribm Gold Belt (93H/4) ...... 99

14 KOO, J.: Telkwa Coalfield, West-Central British Columbia (93L) ...... 113

5 TABLE OF CONTENTS (Continued) PROJECT AND APPLIED GEOLOGY (Continued)

Page 15 Schroeter, T. G.: PorphyryCreek Property (94D/8E) ...... 123 16 Schroeter, T. G.: Toodoggone River Area (94E) ...... 125

17 Diakow, L. J.: A Comparison of VolcanicStratigraphy, Structure,and Hydrothermal Alteration of the Silver Pond (CloudCreek) and Wrich-Awesome Claim Groups, modoggone River (94E) ...... 134

18 Panteleyev, A.: GeologyBetween Toodoggone and Sturdee Rivers(94E) ...... 143

19 MacIntyre, D. G.: A Comparison of the Geologic Setting of Stratiform Massive SulphideDeposits of theGataga District with the Midway andWindy-Craggy Deposits, NorthernBritish Columbia (94F, L; 1040/16;114P/12) ... 149

20 Schroeter, T. G.: Brucejack Lake (Sulphurets)Prospect (104B/8) ...... 171 21 Schroeter, T. G.: Mount JohnnyProspect (104B/llE) ...... 175 22 Schroeter, T. G.: KutchoCreek Property (1041/1) ...... 179

23 Alldrick, D. J.: Salmon RiverProject, Stewart, British Columbia(104B/1) ...... 183

24 Hora, 2. D.: Mapping of Silica Occurrences inBritish Columbia ...... 196

OTHER INVESTIGATIONS

25 Northcote, K. E., Smyth, W. R., andSchmitt, H. R.: RecentMineral Resource Assessment Studies in British Columbia ...... 20 1

26 Watson, P. H. and Godwin, C. I.: Silver-Gold Zonation in the Lass VeinSystem, Beaverdell Camp, South-Central British Columbia(82E/6E) ...... 227

27 Goldsmith, L. B. and Sinclair, A. J.: SpatialDensity of Silver-Lead-Zinc-Gold vein Depositsin Four Mining Camps inSoutheastern British Columbia (82F) ...... 251

28 Cann, R. M. and Godwin, C. I.: Genesis of Magmatic Magnetite-ApatiteLodes, Iron Mask Batholith,South- Central British Columbia (921) ...... 267

6 TABLE OF CONTENTS (Continuned) OTHERINVESTIGATIONS (Continued) Page 29 Sinclair, A. J. andBentzen, A,: A Computer-based Procedurefor Fantifying Geological Data for Resource Assessment ...... 285

30 Sinclair, A. J. andHansen, M. C.: Resource Assessment ofGold-Quartz Veins, Zeballos Mining Camp,VdricoUVer Island - A Preliminary Report (92L) ...... 29 1

31 Andrew, Anne, Godwin, C. I., and Sinclair, A. J.: P.ge and Genesis ofCariboo Gold MineralizationDetermined by Isotope Methods(93H) ...... 305

32 Whittaker, P. J.: Chromite in the Mount Sidney Williams Area, Central British Columbia(93K) ...... 315

7 PROJECT ANDAPPLIED GEOLOGY

GEOLOGY IN THE VICINITY OF THESULLIVAN DEPOSIT KIMFJERLEY, BRITISH COLUMBIA (82F, G) BY T. H8y

INTRODUCTION

The study of the Purcell Supergroup,initiated in 1977, was intendedto develop a betterunderstanding ofthe stratigraphic, structural and tectonicsetting, and orecontrols of theSullivan and c,ther smal.ter but similar clastic-hostedlead-zinc deposits southeasternin 13ritish Columbia.Kanasewich (1968) recognized a basementstructure from anomalousmagnetic and gravity trends and by deep seismic reflections thatcut northeasterly across the more northerlyregional stratigraphic andstructural trends. He concludedthat the structure was a Precambrian rift and thatthe Sullivan deposit originated within it. The p.coposed riftcoincides with the pronounced St. Mary-BoulderCreek and the Moyie- DibbleCreek fault systems that cut across the Purcell Mountains .and the western ranges of the Rocky buntains(Fig. 2). Lowe'r Pa1eozoi.c (for example, leech,1958) and earlier mdrynian movements, generallyblock- faulting and tilting (Lis and Price, 1976),had been recognized along thesetransverse fault systems, but earlier Eurcell age moverrents 'sad not beendocumented. A primaryobjective of this study was todetermine if thesetransverse structures were activein Purcell time andcould thereforehave controlled theregional distribution le.sd-zincof deposits.

*2' ?II

Flyre 2. Location map, shailng St. Mary, Boulder Creek, MoyIe, and Dibble G-eek faults, and published geologlcal map5 In the vlclnlty of the Klmber ley mp-erea.

9 The smdyinitially focused on theKootenay Ranges east of the Rocky MountainTrench and results were releasedas two preliminary maps (Hoy, 1979; McMechan, 1979).Locations are given on Figure 2. Dramaticthick- ness increases and rapidfacies changes in theAldridge Formation (near thebase of theexposed Furcell succession) occur in thevicinity of the BoulderCreek fault. The fault is interpretedto havebeen a growth fault whichdown-dropped thearea tothe south (Hoy,1979, 1982a). Furthersouth, McMechan (1979,1981) recognized that overlying Furcell platformalrocks have similar, though less dramatic,changes. These data tendto confirm the presence of a transversePrecambrian rift structure.

It was suggested (Hoy, 1982b) thatthis transverse zone is marked in Furcellrocks to the west by thepreferential distribution of intra- formationalconglomerate and mrcell sills. It is alsocharacterized by anomalousconcentrations of boronthat are supposedly related to deep crustalfractures (Ethier andCampbell, 1977). Mappingand detailed sectionmeasurements were subsequently begun in the vicinity of the Moyie faultin the Furcell Mountains (Hoy andDiakow, 1981, 1982). The work continuedthis past summer and was extendednorthward to encompassthe St. Mary fault and the Sbllivan mine at Kimberley.Mapping of the Kimberleymap-area is beingcompiled and will be released as a preliminary map (1 :50 000 scale) when conpleted.Further fieldwork on the Purcellproject will be minimaland will onlyinclude fill-in traverses and sectionmeasurements; these will be completednext field season.

The Kimberleymap-area is withinthe Fernie west-half (82G/W) sheet (Leech,1960), and the eastern part of theSt. Mary sheet(Leech, 1957). Many of thesalient features ofthe geology were initiallyoutlined by Rice (1937).Other maps publishedin the vicinity of theKimberley sheet are shown on Fiqure 2.

GIQJERAL GEOLOGY

TheKimberley area(Fig. 3) is transected by theright lateral, reverse St. Mary fault. The faultbrings Lower andMiddle Aldridge rocks in its hangingwall(the St. Mary block of Eenvenutoand Price, 1979) against Crestonand younger Furcell rocks or, locally, Cambrian siltstone and shale of themger Formation. The Sbllivandeposit occurs at the boundarybetween the Lower andMiddle Aldridge within the St. Mary block. It is justsouth of thenorth-dipping, normal Kimberley fault (Hamilton, et dl., 1982).Sullivan is one of the largestbase metal deposits in theworld, having produced in excess of 100 milliontonnes of ore and with remaining reserves of approximately 50 million tonnesgrading 4.9 per centlead, 6.1 percent zinc,and 37 grams silver pertonne (Ransom, 1977;%milton, et al., 1981,1982). The NorthStar andStemwinder depositslie just to the south. They aresmall lead-zinc deposits with less than100 000 tonnesproduction that are situated in theupper part of the Lower AldridgeFormation (see Fig. 3).

10 Figure 3. Geological map ot the Klrnberleyarea.

PURCELL SUPERGROUP STRATIGRAPHY

The stratigraphicsuccession in the Kimberleyarea is illustrated on Figure 4. The oldestrocks, rusty-weathering siltstone, quartz wacke and argillite of the Lower AldridgeFormation, are onlyexposed inthe hangingwall of the St. Mary faultsouth of theSullivan mine.Crossbeds and gradedbeds, and occasional flute casts suggest it consists largely of turbidites. A 250-metre-thicksuccession ofgrey-weathering quartzite andquartz wacke turbiditebeds, which is lithologically similar to much ofthe Middle Aldridge succession, occurs approximately 300 metres below the Lower-Middle Aldridgeboundary. It is well exposed on thewestern andsouthern slopes of North Star Hill and also a few kilometresnortheast ofKimberley.

11 Flyre 4. Stratigraphicsuccession In the Kimberley area

TheLower-Middle Aldridgecontact is poorlyexposed. It cropsout near theSullivan deposit and subcrops on Concentrator Hill east of Kimberley. Stratigraphically, it hasbeen placed below exposures that contain prominent,blocky, grey-weathering quartz wacke beds.Finely laminated pyrrhotite-pyritebeds in laminatedargillaceous siltstone, that may be distalequivalents of the Sullivandeposit, have been described at approximatelythis horizon in two CbmincoLtd. diamond-drillholes that were drilled east andsoutheast of theSullivan deposit (Hagen,1978). Justwest of Lone Pine Hill, the mwer Aldridge is in faultcontact with theMiddle Aldridge (Hagen, 1981 ) .

The MiddleAldridge consists of grey-weathering quartz wackeand quartzite bedswith local interlayered siltstone and silty argillite. It is estimatedto be approximately 2 000 metres thick in thesection southeast of theSullivan mine, where individualquartzite beds are up toseveral

12 metresthick. The thickquartzites may be amalgamated turbiditebeds; that is, they may comprise a numberof individualmassive turbidite beds withouteither intervening silt component orrecognizable graded tops. Coarse (1 to2-millimetre) quartz grains may occurwithin these thicker beds.Measurements of flutecasts at the base of some turbidite beds indicate a northto northwesterly currenttransport direction. I@ section within the Middle Aldridge,the proportion of dark silty argillite increases.Locally it becomes predominant,making it difficultto dis- tinguishisolated outcrops from wperAldridge exposures. The &per Aldridgeconsists of approximately 300 metres of rustytodark grey- weatheringlaminated argillite and silty argillite.

Rocks overlyingthe Aldridge Formation, the Creston, Kitchener, and Van CreekFormations (Fig. 4), aresimilar to those described to thescuth in the Cranbrock area (Hoy andDiakow, 1981,1982). plartzites and siltstones of theCreston Formation are typically green or grey with lesser amounts of mauve-coloured siltstone. Numerous sedimentarystructures indicateshallow marine subtidal to supratidal deposition,3l environments. However, exposures of well-bedded,grey-weathering AE turbidite!; just northwestand northeast of Cranbrook indicate local deeper water environments. The KitchenerFormation is dominantly hffto grey-weat.hering dolomite,dolomitic siltstone andlimestone. The Van CreekFormation is olivegreen, to locally mauve and tan shale and siltstone.

The NicolCreek Formation includes toffs; massive, porphyritic, and amygdaloj.da1basic lava flows; and intercalatedgreen siltstone and quartzite. It thinsnorthwestward fromapproximately 180 metres,north o f Cranbrookof to 36 metressouth of Marysville. Only thebasal few hundredmetres of the overlyingSheppard Formation are exposed in the Kimberleymap-area. 'Ihey consist of lightgreen, tan, an8 lesser purple, finely laminatedsiltstone and argillite.

Purcell basicigneous sills anddykes are prominent in the Lower Aldridge andlower part of the MiddleAldridge, ht uncommon or absent in nuchof theCreston Formation. Similar rocks appear again, probably as a separate intrusive event in the Kitchener and Van Creek Formations. In contrast with MiddleAldridge sills in the Moyie Lake areathat can commonly be tracedtens of kilometres. and aretherefore valuable markers, Ibrcell intrusiverocks in theKimberley area are commonly crosscuttingdykes that changeappreciably in attitude and thicknessas tht?y aretraced in outcrops. They arelocally very coarse grained and plagioclase phenocrysts can be severalcentimetres across.

CAUBRIAN STRATIGRAPHY

The SheppardFormation is unconformablyoverlain by quartzite and aarbon- ate of theCranbrook Formation and shale and siltstone of theEager Formation of Cambrianage. 'Ihe contact, whereexposed north of Cra.nbrook andnear Antwerp Creek south of Marysville, is discordant. The Cra.nbrook Formation at AntwerpCreek consists of an interlayered !sequence c8f pure

13 tofeldspathic quartzite andgreen siltstone. It is overlain by approximately 80 metres of whiteto light grey orthoquartzite whichhas a few impuresiltstone layers near the top. Intercalated carbonate layers occurat the top of theunit. The carbonate is dominantlymagnesite (McCammon, 1964)andone relativelypure section is approximately 7 metres thick. The Cranbrookgrades up intogreen siltstone and shale of the EagerFormation. Dark tolight grey silty argillitecomprises the bulk of the EagerFbrmation. It is generally well cleavedand locally containsprominent cubes of pyrite.

GRANITIC ROCKS

A numberof outcropsof granitic rocks, initially located by Rice(19371, cropout in thevicinity of Cranbrook airportnorth of the St. Mary River. Theirtextures range from aphaniticcoarseto grained and porphyritic,with altered biotite andhornblende phenocrysts. As Rice suggested,these occurrences are probably part of a larger,unexposed granitic body. A pronounced,oval-shaped magnetic anomaly trends north- northeastover these occurrences (see B.C. Ministry of Energy,Mines and Petroleum€?esources/Geological Survey of Canada Map 8469G and Fig. 3). The intrusive rocks straddle the St. Mary fault and therefore will provide a minimum agefor movement on thefault. A megascopically similarstock in the MoyieLake sheet(Leech, 1960; Hoy andDiakow, 1982) has beendated at 122 Ma (unpublisheddate) .

STRUCTURE

TheKimberley area is dominated by a complex arrayoffaults. The largest of thesetrend easterly to northeasterly and areessentially paralleltothe prominent St. Mary and Wyiefaults. However, net movement on these is generallynormal with north side down, in contrast tothe reverse, right lateral movement on the St. Mary and Moyie faults. Apparentnet normal movement on the Kimberley fault has resulted in approximately 12 kilometresstrike separation of the Upper Aldridge across it, whereasright lateral reverse movement on the St. Mary fault hasproduced 12 kilometresof right lateral strike separation (Fig. 3).

Latenorth and northeasterly trending normal faults cut open to moderate- lytight folds with pronounced axial plane cleavage in Crestonand Upper Aldridgerocks west of Cranbrook(Fig. 3). Similarlate faults cut structures anddisplace the Kimberley fault east of theSullivan deposit. Northwest-trendingfaults are conspicuous in the MoyieLake map sheetto thesouth (Hoy andDiakow, 1982).but in theKimberley area, they are only prominent in thecomplexly faulted terrane just northof Cranbrook.

Broadopen folds with pronounced axial plane cleavage occur in both Purcell andCambrian age rocks. In the vicinity of some faults,they become tight,overturned structures.

14 SumMARY

The geoloqy of theKimberley area will be released as ,% 1:50 000 pre- liminaryrap sheet, which will bethe last of a series of sheetsthat outlinethe geoloqy of the Furcell Supergroup in thevicinity of the Sullivandeposit in southeasternBritish Columbia.Future fieldwork, plannedfor 1983, will consistonly of fill-intravers'ss in the myie LakeandKimberley areas, sectionmeasuring, andsampling. Newly acquireddata andpreviously released maps (Hey,1979; WMechan, 1979; Hay andDiakow, 1982) will becombined and eventual1.y published in bulletin form.

The objectives ofthe Purcell study have been largely realized:

(1) lb providedetailed (1 :50 000) geological maps of thePurcell Super- groupin the vicinity of theSullivan and other important lead-zinc deposits. (2) lb presentmodels, based on sectionand paleocurrent measurements, of thedepositional environment of Purcell Supergrouprocks. (3) lb place constraints on andpostulate models for regional stratigraphic,structural, and tectonic controls of mineralizationin the Sullivan camp.

It is concludedthat synsedimentary faulting, perhaps near the northern edgeof a transverserift structure, locally controlled sand modifiedthe distributionof Purcell rocks in Lower andMiddle Aldridge time. Clastic- hostedlead-zinc deposits such as Sullivan,North Star, Stemwinder,and KootenayKing are alsolocated near thenorthern edge of this transverse structure,suggesting a geneticlink between mineralization and syn- sedimentaryfaulting (Hoy,1982a, 198223).

ACKNOWLEIXWZNTS

Discussionswith Cominco Ltd.geologists (J. Hamilton, P. Ransom, G. Delaney, and A. Haqen) at the Sullivan mine helped clarify a number of problems,and the geology inthe vicinity of theSullivan mine (Fig. 3) is from theirpublished work (Hamilton, et al., inpress). Discassions with K. WClay(Goldsmiths College, London, hgland), B. Love11 (Ilniver- sity Minburgh,of Scotland), and L. Diakow (University of Western Ontario, London, Ontario) are gratefullyacknowledged. ?%=cessto unpublished maps (the Dean and All Over claims) ofthe North Star Hill area by AsarcoExploration Company Canada,of Limited is appreciated. Mike Fournierand Ian Webster provided cheerful and ablefield assistance.

REPERWCES

Benvenuto, G. andPrice. R. A. (1979) : StructuralEvolution of the Hosmer ThrustSheet, Southeastern British Columbia, Cdn. Pet. Geol., Bull., Vol. 27, NO. 3,pp. 360-394.

15 B.C. Ministry of Energy, Mines & Pet. Res. and Geological &rvey of Canada,Geophysical Series (Aeromagnetic), Cranbrook, British Columbia,1970, Map 8469G. Ethier, V. G. andCampbell, F. A. (1977) : TourmalineConcentrations in ProterozoicSediments of the Southern Cordillera of Canadaand Tneir Economic Significance, Cdn. Jour. Earth Sci., Vol. 14,pp. 2348- 2363. Hagen, A. S. (1978):Drilling Report, DDCH 6423,Chance No. 5 Group, B.C. Ministry of Energy,Mines & Pet. Res., Assessment Rept. 6786...... (1981) : DrillingReport, Golf 2, Fa110, Fa1 12, DDCH 6444- 6446, B.C. Ministry of Energy,Mines S Pet. Res., Assessment Rept. 971 1. Hamilton, J. M., Bishop, D. T., mrris, H. C., and Owens, 0. E. (1982) : Geology of theSullivan Orebody,Kimberley, British Columbia, in PrecambrianSulphide Deposits, H. S. RobinsonWmorial Vol., R. W. Hutchinson, C. D. Spence,and J. M. Franklin,editors, Geol. ASSOC. Can., SpecialPaper 25. Hamilton, J. M., Eelaney, G. D., Hauser, R. L., and Ransom, P. w. (in press) : Geologyof theSullivan Deposit, Kimberley, British Col- umbia,Canada, in Sediment-HostedLead-Zinc Deposits, D.F. Sangster, editor, Min. Assoc. Can., ShortCourse Notes, Chapter 2. Hamilton, J. M., Hauser, R. L., and Ransom,P. W. (1981) : lhe Sullivan Orebody, in FieldGuide to Geologyand Mineral Deposits, Geol. Geol. Assoc. Can., pp.44-79. Hay, T. (1979) : Ceology of theFstella-Kootenay King Area, mghes Range, SoutheasternBritish Columbia, B.C. Ministry of Energy, Mines & Pet. Res., Prelim. Map 36...... (1982a) : Stratigraphic and Structural Setting of Stratabound Lead-Zinc Deposits in SoutheasternBritish Columbia, C.I.M., Bull., Vol. 75, No. 840, pp. 114-134...... (1982b) : The Furcell Supergroup inSoutheastern British Col- umbia;Sedimentation, Tectonics, andStratiform Lead-Zinc Deposits, in PrecambrianSulphide Deposits, H. S. Robinson Memorial Vol., R. A. Hutchinson, C. D. Spence,and J. M. EYanklin, editors, Geol. ASSOC. Can., Special Paper 25. Hay, T. and Diakow, L. (1981) : Geologyof the MoyieLake Area, Purcell Mountains,Southeastern British Columbia, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1980, Paper 1981-1, pp. 9-14. Htiy, T. and Diakow, L. (1982) : Geologyof themyie Lake Area, B.C. Ministry of Energy,Mines & Pet. Res., Prelim. Map 49. Kanasewich, E. R. (1968):Precambrian Rift: Genesis ofStratabound Ore Deposits, Science, Vol. 161, pp.1002-1005. Kanasewich, E. R., Clowes, R. M., andWCloughan, C. H. (1969): A Buried PrecambrianRift in Western Canada, Tectonophysics, Vo1. 8, pp.513- 527. Leech, G. B. (1957):St. Mary Lake,Kootenay District, British Columbia (82F/9), Geol. .Slzrv., Canada, Map 15-1957.

16 Leech, G. B. (1958) : Fernie Map-Area, West tklf,British Columbia, Geol. SUrv., Canada, Paper 58-10...... (1960) : Geology,Fernie (West Mlf) , Kootenay District, British Columbia,Geol. Surv., Canada, Map 11-1960. Lis, M. G. and Price, R. A. (1976) : Large-Scale Block Faultinghlring Deposition of the Windermere Supergroup(Hadrynian) in Southeastern British Columbia, GeoZ. Surv.,Canada, Paper 76-1A. pp. 135-136. McCammon, J. W. (1964): ?he MarysvilleMagnesite Belt, B.C. Ministry of Energy, Mines & Pet. Res., Ann. Rept.,1964, pp.187-193. McMechan, M. E. (1979) : Geology of themunt Fisher-$:and Creek Area, B.C. Ministry of Energy,Mines & Pet. Res., Prelim. Map 34...... (1981) : The MiddleProterozoic Furcell Supergroup in the Southwestern Purcell Mountains,British Columbia an,3 the Initiation of theCordilleran Miogeocline, southern Canada andPdjacent United States, Cdn. Pet. Geol., Bull., Vol. 29, No. 4, pp. 583-621. Price, R. A. (1962):Fernie Map-Area, =st mlf,Alberta and British Columbia, Geo.1. SUrv., Canada, Paper 61-24. Fansom, P. W. (1977):Geology of theSullivan Ort?body, in Lead- ZincDeposits of Southesternkitish Columbia, r. my,editor, Geol. ASSOC. Can., Fieldtrip Guidebook 1, pp. 7-21. Reesor, J. E. (1958) : &war Creek Map-Area, withSpecial Emphasison the whiteCreek Batholith, British Columbia, Geol. Surv., Canada, Mem. 292, 78 pp...... (1981):Grassy muntain, Kootenay Land D-tstrict, lhitish Columbia, Geol. SUrv., Canada, Open File 820. Rice, H.M.A. (1937) : Cranbrook Map-Area, British Columbia, Geol. SUrv., Canada, Mem. 207,67 pp...... (1941) : Nelson Map-Area, E3st Half,Geol. SUrv., Canad.3, Mem. 228,86 pp. 'A-1 ' BLUEBIRD ADIT AN EXAllPLE OF GALENA-COATED JOINTSRATHW THAN VEINS (823/14)

By G. G. Mdie

The 'A-1' Bluebirdadit (Fig.5) is a new workingdriven byEob Button, Silver Hills Consulting & ContractingLtd., below the Blue-bird A adit which is fiescribedby C. E. Cairnes(1935).

Figure 5. Location map torthe 'A-1' Bluebirdadit tatter Fig. 1, Ca I rnes, 1935).

The mineralizationoccurs in argillites of theSlocan series (Fig. 6). The new showing consists of galenacoating joint planes. One small vein was seenwhich has an extraordinary 17 982ppn silver in the galena.

The mineralsystem was detected by a self-potential test that was runon thesurface, and thepropery warrants further exploration. The joint planemineralization is toonarrow for handpickingthe ore. If production were initiated, a small portable mill wouldprobably be needed to make a concentratebefore shipping.

Assistancein the mapping was given byLloyd Addie.

REpEs(ENcE

Cairnes, c. E. (1935) : Descriptions of Properties,Slocan Mining camp, British Columbia, Geol. Surv., Canada, Mem. 184, 274 pp.

18 I SYMBOLS

ADITENTRANCE ...... STOPED AREA ...... -...... LODE SYSTEM ...... "-..

PORPHYRITICINTRUSIVES (MAINLY1 ...... b v **

LOCATION MAP FROM GEOLOGICAL SURVEY OF CANADA MEMOIR 184, FIGURE 1

Figllre 6. CBoIogy andassay data for the 'A-1' Bluebirdadit.

19 Figre 7. Gaolog ot the Llne Creek area. Elk Valley Coalf leld.

20 LINE CREEK AND CROWN IK)LINTAIN AREAS ELK VALLEY COALFIELD (826/10, 15)

By D. A. Grieve and JanineM. Fraser

INTRODUCTION

The studyarea is in thesouth half of the Elk Valle!{ Coa1fiel.dand adjoinsthe munt Banner area, which wasmapped in 1981 (Grieve, 1982). It includesthe Crows Nest ResourcesLimited Line meelt minesite(not mapped)and severalother properties, including Burnt Ridge, Mount Michael,Line Creek extension, Horseshoe Ridge, wepeel Mountain, and Crown Mountain(Figs. 7 and 8). With theexception of Burnt Ridge, which is freeholdland with coalrights held by B.C. Coal Ltd.,, coalrights in thestudy area are heldunder licence and lease by Crow:; Nest Resources Limited.

~~gure8. Geology of the Crown buntaln area, Elk Valley Coalfield

21 'JJ3 NlVlNflOWISlW I

u W 2 2 5 0 z 0

U LE

Y 2 ", I

f",

22 Crows Nest ResourcesLimited began processing and shipping coal from Line Creekmine inFebruary, 1982. The conpanyhas been a,-tively seeking additionalcoal reserves adjacent to the minesite, andhas undertaken detailedexploration on thenorth part of Line Creek Rit3ge (LineCreek extension),Horseshoe Ridge, and Fbunt Michael. MOreOVEr, most of the study area hasreceived some level of explorationduring the past three years.

LineCreek minesite, which is 24 kilometresnorth-northeast of Sparwood, is accessiblefrom the Sparwood-Elkford Highway. C;ood access is availableinto all parts of the studyarea using exploration, mine, and forestryroads. Elevations in the area range from 1 500 to 2 500 metres.

PIELLWORK

Fielddata collected was plotteddirectly onto British Columbiag3vern- ment air photographs; it will hd transferred later to 10 000-scale orthophotosfor publication to augment results from thelast two field seasons (Grieve, 1981, 1982).Stratigraphic sections of ,:he coal-bearing rocks were measured using pogostick or chain and clinometer.Gmb and channelcoal samples were collected for petrographicanalysis. ksults will beincluded with the 1:lO 000 geologic mapswhen they are published.

STRATIGRAPHY

Sedimentaryrocks of the Jurassic-Cretaceous Kootenay Group conprisethe southeastBritish Columbia coalfields. The KootenayGroup, as defined by Gibson(1979). consists of the Morrissey, Mist Mountain,and Elk Forma- tions.

The basalMorrissey Formation is a prominent,cliff-forming sandstone unit that consists of the Weary Ridge and Moose Mountain members. Pre- viouslyunrecorded occurrences of a pebbleconglomerate facies oE Moose Mountain member were noted at thesouth end of BurntRidge and onTeepee Mountain. A recessiveinterval of 3 metres thickness, ,which includes a carbonaceouszone, occurs 8 metres below thetop of tht? kose Mmntain member atthe south endof Wlrnt Ridge. It probably c:orrespond!j to a thincarbonaceous shale and coal partingthat occurs h'ithin the Moose Mountain member at Line Creekmine. Although it is of no economic significance, it may affectstability of a mine slope OK a wall formedof the basalsandstone.

The overlying Mist hbuntain Formation,which consists of interbedded sandstone,siltstone, nudstone, shale and coal, is on ithe order of 500 metres thickin the study area (Fig.9). ?WO complete sectionsmeasured west of the trace of the Ewin Passthrust (A and B on Fig. 9) are 587and 550 metres respectivelyin thickness. The one conpletesection measured

23 east of the Ewin Passthrust (D on Fig. 9) is only 430 metres inthickness. 'Ihiscontrast is similarto that reported from northof the study area(Grieve, 1982).

A 217-metrezone with no coal seamsforms the immediatehangingwall of the Ewin Passthrust at section C on Mount Michael(Fig. 9). Correlation betweenthe barren zone in section C and sections A and B is uncertain because no conparablezone occurs in these sections. North and south of section C, where thefault is locallylower in thestratigraphy, a thick- enedcoal seam ofup to 20 metres apparentthickness occurs. Approxi- mately 12 coalzones, including nultiple seams,occur in theupper 250 metres of Mist MountainFormation insection C, sections A and B have fewer cooparable seams.

Thereare also striking contrasts between section C, inthe hangingwall, andsection D, inthe footwall of the Lkin Passthrust, respectively. The upperplate on MOunt Michael is readilydistinguished fromthe lower platebecause there are numerous coal seams in thetop 150 to 250 metres of theupper plate.

No cooplete Mist Mountain sectionsare exposed on HorseshoeRidge, Teepee Mountain, or Crown Mountain. Horseshoe kdgecontains an estimated 350 to 400 metresof section, of which the lowest 311 metres were measured (E onFig. 9). A resemblanceto the lowest 250 metresof section on Mount Michael (D on Fig. 9) is apparent,although significant facies changes haveoccurred between the two sites.

Similarly,there are no conplete Elk Formationsections in thestudy area.Inthe Mount Banner areatothe north, the ElkFormation is estimatedto be on the order of 300 metres in thickness.Strata of the ElkFormation are similar in most respectsto those of the Mist Mountain Formation. The presence of Elk coal,an alginite-rich cannel coal, is used to distinguishthe Elk Formationfrom the Mist MountainFormation. Othercriteria include a lackof coal seams greaterthan about 1.5 metres in thickness in the Elk, a greater numberof sandstone units, and the presence ofa pebbleconglomerate, whichcrops at inthe core of the Alexander Creek syncline tothe east of section B.

The contactbetween the Mist Mountainand Elk Formations is generally placedeither at the firstoccurrence ofneedle coal or at a locally mappable,resistant sandstone unit whichappears to separate strata of the two formations.For example, a veryprominent series of resistant channelsandstones defines the contact immediately north of Noname Creek.

The studyarea is part of the Lewis thrustplate; the Alexander Creek syncline is the dominantstructure. In thenorth part of thearea the foldaxis plunges to thenorth downDry Creek(Fig. 7) as it passes

24 betweenFhrnt Ridge (west limb) and Mount Michael (east 1.imb).South of Noname Creek it passes throughthe east slope of LineCreek Ridge, where it separates LineCreek minesite (west limb)from Horseshoe Ridge (east limb). Near LineCreek the axis is truncated by the Ewin Passthrust. Its tracebeneath (east of)the thrust is not clear, although two very thinremnants of KootenayGroup on Teepee Mountain are in a generalbut irregular synclinal configuration (Fig. 7).

AlexanderCreek syncline is well definedin the upper plate of the major thrust at Crown Mountain(Fig. 8). The lower plate at thispoint is a west-dippingmonocline.

The second major structure in thestudy area is thewest-dipping Ewin Passthrust (Fig. 7). Its most significanteffect was to emplace Mist MountainFormation over Elk Formation on Mount Michaelwith approximately 600 metres of verticaldisplacement. As a result, numerous coal seams occurin a settingthat is suitablefor open-pit mining. Contrasts in thicknessand lithologies of Mist Mountain Formation sections aboveand belowthe Ewin Pass thrustfault (C and D on Fig. 9)suggest that there was a significanthorizontal displacement.

To thesouth of Mount Michaelthe Ewin Passthrust cuts down-section with loss inelevation. South ofLine Creek it rmst be withinthe 'Fernie Group. It is notentirely clear at this time ifthe thrust at Crown Mountain is alsothe Ewin Pass thrust; it emplaced thetop part of the Fernie Groupand basalpart of the Kootenay Group overthe basal part of the Kootenay Group withapproximately 200 metres verticaldisplacement (Figs. 7 and 8).

Asidefrom stratigraphicevidence, the Ewin Passthrust is also recognizablein the field because of associated complex, small.-scale deEorma- tionfeatures including drag folds, overturned zones, andthickened and sheared coal seams. Similar features also characterizerumerous smaller thrustzones in various parts of thestudy area, particularly in the east limbofthe Alexander Creek syncline. Other smaller scale structural conplicationsin the area include a faulted, tight syncline affectilng the Morrisseyand basal Mist MountainFormations at thesouth endof 'Horse- shoeRidge; it may also berelated to movement on the ENin Passthrust. Of note are numerous thrust-relateddisplacements and repetitions of the MorrisseyFormation (Fig. 71, and a series of post-thrusting,crosscut- tingblock faults in the Crown kbuntainarea (Fig. 8). The significant overturnedpanel found on mrnt Ridge (west limb)to the north (Grieve, 1982)does not extend into the study area.

We greatlyappreciate the field assistance of azanne Cannon andl Greg Campbell. Crows Nest ResourcesLimited staff are thanked for permitting access tothe Line Creek mine area.

25 REFERWCES

Gibson, D. w. (1979): Ihe Morrisseyand Mist MountainFormations - Newly DefinedLithostratiqraphic Units ofthe Jura-Cretaceous Kootenay Group,Alberta and British Columbia, Cdn. Pet.Geol., Bull., Vol.27, No. 2, pp.183-208. Grieve, D. A. (1981) : ElkValley Coalfield, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1980, Paper 1981-1, pp. 70-72...... (1 982) : Mount BannerArea, Elk ValleyCoalfield, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1981, Paper1982-1, pp. 47-50.

26 GEOLOGY AND MAGNETOMETER SURVEY OF THE SAPPHO GOLD-SILVER-PLATINW-COPPER PROSPECT ( 82E/2

By B. N. Church and S. Robertson

INTRODUCTION

Thisreport describes results ofa geological and magneto~netersurvey of the SapphoCrown-granted claim located near the International Eoundary, approximately 4 kilometressouth ofBoundary Falls and5 kilometreseast ofthe town of Midway.The claim is currentlyundergoing re-examination forcopper and precious metal potential by KettleRiver Resources Lt.d.

HISTORY

According toMinister of Mines reports, 100 tonnes of oregrading approximately 53 ppm silver and 6 percent copper wereshipped to the smelter fromthe Sappho claim (MI 82E/SE-147) duringthe period 1916 to 1918. Workings on theproperty consist of severalpits, a shaft, and an. adit dating from1927 and earlier. A grabsample of oretaken fromone of the pitsassayed 3.2 percent copper and 0.9 ppm platinum.

Recent work includestrenching, drilling, rock sampling, and geological andgeophysical surveys. In the period1963 to 1964,Triform MiningLtd. andCoast Eqloration Ltd. reported results on theirtrellching and. rock samplingprogram. Apparently one 15-metre section assayed 0.2 per cent copper, a secondsection of 6 metresaveraged 0.44 percent copper, and a thirdsection of 6 metres averaged 0.8 percent copper. The operators alsoreported a shorthigh-grade sulphide drill hole intersection assaying 28 ppm gold.

Rock samplingperformed by SilverStandard Mines,Limited in 1967 appar- entlyyielded 0.7 percent copper across 9.5 metres in ii trenchnear a north showing and 0.1 5 percent copper across 17 metres in a trench on thesouth part of theclaim (see Fig.10).

Additional work was performed inthe period 1975and 1978 by C.O.M. Stewart and McIntyre Mines Limited. They confirmed the presence of platinum,quoting values for this element in therange 0.6 to 1.8 ppm from spotsampling.

KettleRiver Resources Ltd. acquired the Sappho claim and thesurrounding area in 1981 andrenewed explorationactivities.

GEOLOGICAL SEl’l’ING

Bedrockexposure in the Sappho area is minimal,revealing only fragments of the geologicalpicture from scatteredmtcrops in trenches, in pits, and on a few hilltops (Fig. 10).

27 Figure 10. Geolog and magnetonetersurvey ot the Sapphoprospect.

28 ?he principalrock types are a microdiorite, whichforms a stock that is exposed inthe central area andnear the southeast corner of theclaim, andyounger (Eocene) Cbrye11-type bodies. Greenstones hosting both intrusions are exposednear the east boundary of the c.taimand :in the south-centralarea. Scattered occurrences of serpentinitehave been reportedin the northern area where chloritizedrocks with mineralization are also found.

The mineralized area is delineated on the east by the eas$:-bounding fault ofthe 'Ibroda Creek graben and on thenorth by a majornortheast-trending fracture.Tertiary rocks are found to thenorth and include a hill of brecciated basement rocksof apparent landslide origin caused by major faulting (Monger,1968, p. 27).

MINERALIZATION

TheSappho prospect is oneof the few known occurrences in the province of lode-typeof copper-platinum mineralization associated with alkaline intrusions.Other examples are the Maple Leaf showing inthe EYanklin camp north of Grand ForksandtheCopper bbuntain depositnear Princeton.

Coryell alkaline intrusions at Sappho host the mineralization both at the central showingsand near the northeast corner of the claim. The princi- palphases of the Coryell rock are pyroxenite(sh0nkinit.e) and pyroxene monzonite.Subsidiary phases include small peqmatoidamphibole-rich segregations and alkalifeldspar-rich differentiates that commonly occur as dykesor apophyses.

Mineralizationconsists ofpyrite-chalcopyrite disseminated inshear zonesand forming irregularly shaped blebs and pods ofsulphide in biotiteshonkinite and sericitized feldspathic phases. sulphides are also foundlocally in skarn-likeassemblages of chlorite, epid,>te, garnet, and magnetitenear what appear to be intrusive margins. Vei:llets of calcite are common in the mineralizedareas, however, quartz veins are few.

Relations betweenserpentinite and mineralization are uncsrtain. Eerpen- tinitefragments, which are common in the dumps of some oldcol.lapsed excavationsin the northeast area, are evidence of shearfin9and probably a major fault zone.

MAG- SURVEY

A magnetometersurvey was conducted on the Sappho property to complement thegeology, which is poorlyunderstood because ofextensive qlacial cover.Existing roads and the surveyed line system were utilizedfor access andgeographical control. Standard field methods were employed using McPhara 700 fluxgatemagnetometer with vertical sensorconfigura- tion.

29 The results of a scattering of 146 stations across the area show a range ofapproximately 4 000 gammas (that is, 36 to -4 scale divisions). The magneticcontours shown on Figure 1 were generatedaccording to the mov- ingaverage procedure using a computerprogram described in Geological Fieldwork,1980 (B.C. Ministryof Energy, Minesand Petroleum Resources, Paper 1981-1,pp. 25-32) using a 50-metre radial integrationdistance and a radialweighting factor calculated as follows:

the moving average = T/S S = S + (l/R) the sum ofweighted factors and T = T + [A*(l/R)Ithe sum of weighteddistances, R beingthe radius of integration and A thefield readings within the area ofintegration

Two typographicalerrors in theoriginal printing of the computer program (Table 1, p. 27) are as follows:

Line 160 statement IF SQR (A(1) - + (2(2) - Q*;) shouldread IF SQR (A(1) - p) + (A(2) - Q) Line 220 statement P = P + 0 shouldread P = P + 1.

The survey shows a magnetic low immediately east and south of the north-. ern mineral showingsand trenched area, a magnetic trough to the northwest coincidentwith a topographic lineament, andwhat appears to be a magneticdipole inthe area of nicrodioriteexposures near the south boundaryof the map-area. The resultsappear to confirm the previously inferredposition of a majorfault on thenorth. They alsosuggest that thechloritized contact zone extends to the east and southof the northern trenchesand may extend to zonesof faulting or alterationrelated to thecontacts of the microdiorite. The featuresoffer somenew interpret- ationsof the geology and re-evaluation of explorationtargets.

REFERENCES

Minister of Mines, B.C., Ann. Repts., 1916, p. 518; 1917, p. 449;1918, p. 211;1927, pp. 234, 235;1928, p. 250; 1964, p. 110; 1967, p. 226. B.C. Ministry of Energy,Mines & Pet. Res., Exploration in B.C., 1975, pp.El2, E13; GeologicalFieldwork, 1980. Paper 1981-1, pp. 25-32. Church, B. N., Fahrni, K. C., andFTeto, V. A. (1982): Guidebookof CopperMountain and Phoenix, Geol. ksoc. Can., MineralDeposits Section, 72 pp. Dobrin, M. B. (1960):Introduction to GeophysicalProspecting, McGraw- Hill, 446 pp. Gilmour, W. R. (1981) : The SapphoProperty, Norwegian Creek, Greenwood MiningDivision, B.C. Ministry of Energy,Mines & Pet. Res., Assess- ment Rept. 9364, 18 pp. Jakosky, J. J. (1980):Exploration Geophysics, Trija Pub. Co., California 1195 pp.

30 Lahee, F. H. (1941):field Geology, McGraw-Hill., 853 pp. McPhar Geophysics Co. Ltd., Manual to the M70O Mgnetometer,12 pp. Monger, J.W.H. (1968):Early Tertiary Stratified Rocks, Greenwood Map- Area, (823/2),British Columbia, Geol. %rv., Canadd, Paper 67-42, 39 PP. O'Neill, J. J. (1918): 'Ihe PlatinumSituation in Canada, Geol. Surv., Canada, Summ. Rept., 1918,Pt. G, 19pp. Paxton, J. (1971) : A Geochemical Report on a Geochemical. Soil Survey on the KIS Claim Group forthe GranbyMining Co. Ltd., B.C. Ministry of Energy,Mines & Pet. Res., Wssessment Rept. 3335, 6 pp. Seraphim, R. H. (1967) : hp of theCabin Claims, Silver Standard Mines, Limited, private company rept. (unpublished map).

31 TABLE 1. CHEMICALANALYSES OF BASALTS FROM THEOKANAGAN HIGHLANDS

1 2 3 4 5 6 7 8 Oxldes recalculated to 100 SI02 47.84 48.30 48.69 49.77 48.63 49.67 50.09 50. 85 TI02 2.21 3.21 2.07 2.06 2.00 3.06 2.35 2.48 AI 203 17.08 17.22 15.93 16.44 18. I6 17.84 16.21 17.58 Fe203 4.56 4.62 2.95 5.40 3.34 4.57 4.28 4.14 FeO 8.31 9.01 9.28 9.17 8.90 7.67 8.08 7.79 MnO 0.18 0.20 0.18 0.22 0.19 0.18 0.18 0.23 Mg 0 6.65 4.40 6.96 3.88 5.22 4.18 6.31 3.95 CaO 8.56 7.51 8.74 6.95 8.14 7.46 6.60 5.86 %Q 3.61 4.08 3.88 4.35 4.06 4.18 4.21 5.04 K20 1.00 1.45 1.76 1.32 1.36 1.19 1.69 2.08

Oxidesas determined H20+ 1. 13 1. I8 0.60 1.21 0.82 1.11 1.70 1.07 Hz* 0.68 1.00 0.50 0.79 0.73 0.78 1.03 0.81 c4

Molecular Norm

Or 5.94 8.69 7.80 10.55 8.06 7.1 I 10.00 12.32 Ab 32.56 37.14 33.11 39.62 34.31 37.94 37.84 4242 Ne - - I .02 - 1.34 - - 1.75 An 27.60 24.75 2216 20.44 27.40 26.71 20.39 19.26 wo 6.02 5.2 1 8.47 5.82 5.24 4.28 4.96 3.95 En 3.42 2.01 - 2.38 - 7.78 3.70 - FS 1.23 1.04 - 1.69 - 3.00 1.33 - Fo 11.27 7.73 14.41 6.36 10. 84 2.92 10.31 8.20 Fa 4.06 3.99 7.08 4.50 6.52 1.12 3.7 I 4.3 1 I1 3.09 4.53 2.88 2.91 2.79 4.31 3.28 3.46 Mt 4.79 4.90 3.08 5.73 3.50 4.83 4.48 4.34 Car ------

Key to Analyses

1. Pyroxene-llvlnebasalt on bong kbuntaln,east of Qama bke. 2. Pyroxeneollvlnebasalt east of HarrlsCreek. 3. &versedollvlne basalt above KingEh*ard Week, south of Coldstream (K/Ar whole ro& date of 20.4f1.4 Ma). 4. Basalt with bladed plagioclase phenocrysts west of Oyam Lake. 5. Ollvlnebasalt 5 kl lomtressoutheast of (bidstream. 6. Pyroxeneollvlnebasalt 7 kllomtres southeast of Coldstream 7. Basaltwlth lherzollte lncluslons In the alzzly Hills area. 8. Ollvlne basalt west of Oaves Creek (K/Ar whole rod date of 14.920.9 Ma).

32 GEOLOGY AND I4AGNETOSTRATIGRAPHY OF UIOCENE BASALTS OF THE OKANAGAN HIGHLANDS, BRITISH COLUMBIA (82L/2, 3)

By B. N. Church and U. Suesser

Several outliers ofMiocene basalt havebeen delineated by recent mapping in the Okanagan Highlandssouth and southeast ofVernon. lhe totalarea, underlain by lavasand breccia, is about 200 squarekilometres (Fig. 11). Locallythese volcanicrocks, which range in agefrom 14.9 to 20.4 Ma, weredeposited on placer-bearing gravels. Generallythey cover a rolling terrane of crystallinebasement rocks. The basaltformation, divided locallyinto three members by interbeddedvolcaniclastic rocks, has a maximum thickness of about 340 metrescomprising more than 15 individual flows(Fig. 12).

The basaltsrange from vitrophyrictosugary-textured varieties, the latterhaving greatest magnetic susceptibility. A few lavaflows are characterized by largebladed phenocrysts of plagioclaseor,less commonly, lherzolitexenoliths. Chemical analysis show that most of the rocksare normal olivinebasalts (Table l), although fewa samplesare slightlyenriched in alumina and alkalis.

Preliminarymagnetostratigraphic studiesusing a fluxgatemagnetometer indicatethat the placer gravels areassociated with'reversed' k'asalts ofthe lowest member. Younger basalts in thesuccession have 'normal' polarity, however,magnetic vectors show markeda range in azimuth and angle ofplunge (Fig. 13). Success in themagnetic determinations was dependent in largemeasure on thenear horizontal beddinq of the k'asalts whichdid not require arbitrary rotation of magneticvectors or other manipulationof the data to restore bedding attitudes. Corrections for azimuthmeasurements from sun bearings at sample statims wereapplied accordingto the computer program in Table 2.

TABLE 2. CWUTER PROGRAM FOR SIGHT REDUCTIONCALCULATION OF SLlN AZIWTHS

5 SELECT D IO SELECT PRINT21 I( 156) 20 PRINT'SIGHT REDUCTION CALlLATION FOR SUNAZIMU1-H 30 INPUT 'DAY OF YEAR, I C 40 INPUl'TIME IN HOURS DECIMALS,' A 50 INPUT 'LONGITUDE IN DECIMALDEGREES, * B 60 INPUT 'LATITUDE IN DECIMALDEGREES,' L 70 H = IY(A-12) + (120-8) 80 D = -23.5*C0S(O.O2YCtC) 90 T = ARCSIN((SIN(O)SIN(L)~OS(D)FOS(L)FOS(H))) 100 X = ARCCOS((SIN(D)-SIN(L)*SIN(T))/(COS(L)"COS(T):I) 110 IF H=O THEN 140 130 Z = X: FRINT 2 135 END 140 Z = 360-X: PRINT 2: GOT0 135

2 33 34 I /

Figure 12. [*I11 hole sectlons of basaltand channeldeposlts.

\ /

POLEPLOT aFREOUENT 0 NORTHSEEKING INFREOUENT SOUTHSEEKING

Figure 13. Magneticvectors in basaltIavas.

35 Miningexploration is focused on goldand uranium-bearing stream channel deposits below the basalt. %e King Edward placer (latitude 50 degrees, 11.3minutes; longitude 119 degrees, 11.2 minutes)south of Coldwater is a typical example. The placer goldoccurs in loose sand, pebbles, and cobblesweathered from a Mioceneconglomerate channel underlying the basaltbluff overlooking King Edward Creek. The channeldeposit, which has a maximum thicknessof about 160 metres, hasbeen prospected along strike for about 2 kilometres,and is currently workedon a small scale byHarry Arnold of Vernon. In the late 1970'sthe same channel was the target of a uraniumdiamond-drill program.

Winfield placers are nearthe base of thebasalt bluff northeast of Winfield(latitude 50 degrees, 3.5 minutes;longitude 119 degrees, 19.7 minutes). A buriedfluvial deposit is thesource ofthe placers. It consistsof light-coloured sandstones with conglomerate beds with abun- dantquartz clasts. According to Jones(1959), more than 2 300 gramsof gold were obtainedbetween 1933 and 1945from a series of small adits.

The exactage of some of the channel deposits is controversial. Two deposits ofpolymictic conglomerate, shale, and sandstone in the Harris Creek area are associatedwith an Eocene rhyolite complex dated at 48.3 Ma. Pdjacentand overlying Miocene basaltlavas have'normal' polariza- tion,unlike the lower basalts in the Winfieldand midstream area. Placer potentialin such Eocenechannel deposits is thought to be low. Theyprobably form part of the Eocene highlandterrane uponwhich the Miocene basalts were deposited.

ACKN-

Thanks are owing to Ken Daughtryand William Gilmourof K. L. Daughtry and Associates Ltd. in Vernon forguidance and much helpfulinformation on thegeology and mineral deposits of the Okanagan Highlands.

REPERWCES

Collinson, D. W., CYeer, H. M., andRuncorn, S. K. (1967): Methods in Paleomagnetism,Elsevier Pub. Co. Jones, A. G. (1959):Vernon Map-Area, British Columbia, Geol. Surv., Canada, Mem. 296, 186pp. Okulitch, A. V. (1 979) : Thompson-Shuswap-Okanaqan MineralOccurrence Map, Geol. S~rv., Canada, Open File Map 637c. Suesser, U. (1980):Techniques in Collection and Preparation of Basalt Samples for Determination of Remnant MagneticPole Orientation, University of Victoria, Rept. on Co-op Project,12 pp.

36 LEECH RIVER AREA, VANCOUVER ISLAND (92B/5, 12)

By G.E.P. Eastwood

INTRODUCTION

Placergold was minedfrom the Leech River in quantity in 1864and has beenthe object of intermittent prospecting and small-scale miningsince then. The river name has been usedfor the metasedhnentary hedrock formation onwhich the placer deposits rest and for a majorfault which juxtaposesthe LeechRiver Formation against the Ebcenei-letchosin basalt to thesouth. TheLeech RiverFormation hasnot been dated, and suggestions as to its age haveranged from Carboniferous to Cretaceous. The formationcontains numerous quartz veins carrying txace amountsof gold,and Clapp (1917) concluded that the placer gold was derivedfrom them.

In 1981and1982, fourplacer minerscontinued to wxrk sections of MartinsGulch, when the volume of water permitted.After years of prospecting, RDbertEeaupre had by the endof 1981fourtd gold in small quartzveins in rocks of the Leech RiverFormation west of the upper LeechRiver. In1982 Grizzly Pock ServicesLtd. started to drive a water-supplytunnel for the Greater Victoria Water District. It wi.11 run fromDeception Gulch toward the end of the new roadalong the north side ofthe Leech River. In 1981 the writer made a reconnaissancesurvey of a strip betweenthe mouth ofthe West Leech Riverand the Sooke River.In 1982the reconnaissance across the Leech River Formation was completed to SookeLake. Sections of thetunnel were mapped, and a detailedsurvey was made of thelower part of Martins Gulch (see Fig.14).

The area may be reachedfrom Shawnigan Lake Road via SookeLake Main and Leechtown Main. The formerbridge over the upper Sooke River is, gone, butat low water theriver can beforded by truckimmediately above its confluence with the Leech River. Alternatively, access was from Saoke viaPacific Forest Products'Eoneyard road. As hauling was in progress on week days, a radio was borrowedfrom the company.The Greater Victoria Water District haslocked gates at the Sooke Iakespj.llway, north ofMacdonald Iake,and on theroad along the north side of the LeechRiver due south of Macdonald Lake. Inaddition to borrowing keys, it was necessarytoobtain permits forspecific days to enter the watershedbehind the spillway gate and the Macdonald Road gate.

The principaltopographic features in thearea are a ridgeinthe northwest,the valleys of the Leechand Sooke Rivers, and a largebasin betweenthe tunnel portal and SookeLake. Macdonald Idke lies on the levelfloor of a valleythat separates the ridge from ,3 low, irregular hill to the east. MartinsGulch is actually a V-shaped creekvalley with a moderategradient. Cutcrop is semicontinuous in thelower half of the gulchand along the section of the LeechRiver between the end of the

37 38 north-sideroad and lowest outcrop area shown on Figure 14.Exposure is fairly good tothe south and east ofSooke Lake and in roadcuts between thecabin and a point west ofMacdonald Lake. Elsewhere outcrop is patchy or nonexistent.

GENERAL GEOLOGY

The leechRiver Formation in this area consistsmainly of deformedand metamorphosedmixed clasticsedimentary rocks. Distinct layers of metamorphosed tuff andvolcanic breccia are exposed in Msrtins Gul.ch and on Leechtown Main.Unbedded lightgrey bands in the first few metres of the water tunneland in exposuresaround the portal may also havebeen tuffs. Unbedded greenishgrey schists in the spillway and northalong Leechtown Main are evidentlyClapp's 'Malahat volcanics.' Northward theseschists are increasingly granitized and pass gradationallyinto graniticrocks that Clapp assignedtothe Cblquitz. Thin sheets of slightlygneissic granitic rock are exposed in a road cut on thenorth side ofthe Leech River about 800 metres west of the new bridge.

Mixingof the sediments was accomplishedmainly by interbeddingbut also byincomplete or poorsorting. Definite graded bedding was notfound. The rocks are describedin terms theofmetamorphosed end members, quartzite, siltite, and argillite. The quartzites are Einegrained and medium greyto white in colour. The thickerquartzitt? units commonly have a massivecore, with beds above and below delineated by partingsof siltite or argillite. lhe siltites are generallydark grey to black, but are medium tolight grey along the Leech River,and, in one distinctive unitin Martins Gulch,they are yellow. lhey are uniformlythin bedded. The argillites are black,do not show internalbedding, a.nd are ph!yllitic toschistose.

The well-exposedsection in Martins Gulch was mapped indetail to serve as a reference section. Numerous dragfoldsindicate that the :section faces uniformlyto the north. Definite stratigraphic tops were notfound but,assuming the whole section is notoverturned, the foldpattern is that ofyounger beds riding southward over older toward the crest of an anticline. The rocks were groupedinto stratigraphic packages referred to as units.Since the base of the leech River Formaticm is notexposed andthe upper part is poorlyexposed, any system of designation has to be arbitrary. The distinctivevolcanic unit was assigned No. 100,and the otherunits numbered accordingly. An inferredfault bethzeen units 75 and 76 may signify a gap,but otherwise the section appears to be mostly complete. The units are shown in plan on Figure 15 and theirli-tholoqy is summarized inTable 1. The difference in elevationbetween the base of unit 104and theroad embankment is about 150 metres.

The contactbetween units 66 and 67 canbe identified ne8.r theend of the north-sideroad and less confidentlyin the exposures 800 metres west of the new bridgeover the leech River. Using the traces of this (contact derived on Figure14, the quartzite unit south ofMacdcnald Lake should

39 correlate with any or all of units 84, 86, and 88. Correlationof the volcanic unit on Leechtown Main with unit 100 is thereforepossible, although it is notexposed on the road near MacdonaldLake. The tunnel as shown represents its positionin mid-June. The inner part is mainly siltyargillite andargillite, with interbands of siltite. Threequartz- ite unitsbetween 690 and 500 metres fromthe portal are comparablewith quartziteunits in Martins Gulch. Ihe outer part of thetunnel is driven throughargillite and siltite, andexposures around the portal are mostly argillite. A coveredsection northeast of this is probablyunderlain by recessiveargillite. The volcanicrocks overlie silty argillite at the junctionof the sooke Lake andkechtown roads, but quartzite and siltite onthe Canadian National Railway line to the east, indicating a discon- f ormi ty.

TABLE 1. STRATIGRPPHICSECTION IN LWER MARTINS GULCH

Unit Litholog

104 blnly black argl Ilite, with minor quartzite interbedded I'n the lower part and greenish beds, probably altered tuffs, lnterbedded in the upper part of the exposed section. 103 bstly thinly Interbedded quartzite and argllllte, with dark grey si itlte at thebase and interbedded quartzite and dark grey slltite at the top.

102 lnterbedded light grey slltlte md black argilliteIn the lower part, overlain by mostly argl I lite

101 Mainly dark si ltite and less quartzite; layers of argi I I ite near base and In theupper third

100 Pard light green tuff and volcanic breccia.

99 binly dark grey SIItite.

98 Argillite, silty in lowerpart.

97 Mainly si ltite and quartzite, both interbedded and as separate layers. Minor layers of argi Ilite and argi Illte interbedded with quartzita

96 Mainly argillite; minor Interbedded slltlte and quartzite.

95 Olartzlte. 94 Lower part:argillite, in part interbedded with siltite. Mlddle part:Interbedded argi Illte and quartzite +per part concealed

93 Mainly quartzite, with si ltlte atbase and top.

92 Sandy siltite In lower half and mainly interbedded slltlte and argl llite In upper half.

91 Palnly argillite, silty in part; some interbeddedquartzlte in middle and at top.

90 Qartzlte Interlayered with less si Ity argllllte.

89 Sandy slltite interlayered with less silty argllllte, argillite, and quarztlte

40 TABLE 1. STRATIGRPPHICSECTION IN LOWER MARTINSGULCH (Continued)

Unit Litholog

88 Mainly quartzite; lnterbedded with dark SI ltlte In upper part.

87 Isrk grey and black slitite. bout 50 perCent exposed.

86 bstiy grey quartzite, with some Interbedded dark grey slitlte.

85 Larerhalf: silty argillite; upper half:thinly Interbedded siltlte and quartzite with an interlayer of silty argl lilt6

84 Qartzlte.

83 Si ity argl lllte contalnlng Interlayersot ye1 low quartz51 Itite.

82 Mainly quartzite; some Interlayered dark grey to black si Itlte.

81 ~glIllteandslltyarglllite.

80 Dark grey si ltlte containing quartzite beds and layer.

79 Prgllliteandslltyargllllte.

78 Vainly conpact quartzite.

77 Mainly black argi iiite; some quartzite interbedded in uppsr part.

76 Malnly conpact, cllff-formlngquartzite; In part dirty andInterbedded with si ltita

75 Prglilite containing beds md lenses of quartzite.

74 Canpact interbedded siltiteand quartzite with thinly foliated slltlte at base and top.

73 Interbedded quartzite and argillite In lmer part, overlaln by silty argl I I it5

72 Mixed unit, ranging fromquartzite at base and top to argl lllte in upper half.

71 Mainly argl I laceous; maln ly Interbedded quartzite and 51 Ity argl I I ite In laer part; mainly argilllte in middle; mainly Interbedded quartzite and argl liite In upper part with some Interlayered quartzite and si itita

70 Mainly quartzite, massive to slabby; 51 ltlte layer at base;minor I nterbedded argi I I ita

69 Prgi I I ite.

68 hndy 51 ltlte and interbedded quartzite and si Itite.

67 Silty arglliite, with Some interbedded quartzite in upper part.

66 Mainly slltlte with some Interlayeredarglllite.

41 SYMBOLS \

XE001NG: UPRIGHT,OVERTURNED . . ,Yr JNlTCONTACT ...... / 89

IVERTURNEDSYNCLINE, . . , ;b/

'RACTURE ...... ,--*'

:AULT ......

JNlTNUMBER...... PO

50 100 O,. O,. METRES

Figure 15. Geology of krtins TuIch (for location see Fig. 14).

42 STRUCTURAL GEOLOGY

Overall,the Leech River beds dip and facenorth-northeast at moderate to steepangles. Locally they have overturned, steep south dips. The structuralbehaviour ofthe rocks is well displayed in Martins Qdch. Massivequartzite does not show foldingwithin outcrop limits. Bedded quartzite is commonly closelydragfolded, with limb dips decreasing to as little as 20 degrees in thecentres of some units. The combinationof low internaldips and piled-updragfolds has greatly increased t:te out- cropwidth of many of thequartzite units. Siltit.es and isolated quartzite beds have been thrown into dragfolds that a.re approximately isoclinal,with limbs nearly parallel to an axialplane cleavage. The contactdips shwn on Figure 15 arethose of nearbyunfolded beds. Beddinghas not survived in theargillites; they show only a cleavage or schistosityparallel to the axial plane cleavage. Ihe :largestfold seen in Martins Gulch is anoverturned syncline in quartzite :in theupper part ofunit 72. Sincethe lithology does not repeat north of thisquartzite andquartzite beds in unit 73 show dragfoldsindicating overriding to the south, it is assumed thatthe corresponding anticline has been sheared outalong the axial plane cleavage. Some largerfolds are indicated in thesections west andsouth of MacdonaldLake and alongthe sooke River byreversals in the direction ofoverriding, but they do not appear to repeat whole units.

At the mouthof Martins Gulch, inthe LeechRiver, the structural style changes. In thegulch section most dragfoldsare complete, whereas in theriver mosthave been pulled apart, leaving only rod-like thickened axialportions. Also, dragfoldsare morenumerous, smaller,and tighter in theriver. Finally, there is a progressivechange in dip of foliation and remnant beddingacross the riversection. Dips aresteep north on thenorth side but steep south on thesouth side, near the Leec'h River fault. This changed style is interpretedto represent a superimposed seconddeformation in responsetoinitial compression and subsequent tensioncaused by movement on thefault (Eastwood, 1982).

Quartzveins are common in all the rocks, but they are more abundant in argilliteunits. In the Martins Gulch sectionthere appears to have been little or no movement in theargillites after deposition of quartz veins along the foliation. In contrast,quartz in theouter part of the water tunnel is in lenses and theschistose argillite has beenwrapped around them, creating a wavy tocurly schist. Post-quartz movement is indicated by a highpolish on theschist surface against the quartz. This slick rockpresents a ground-supportproblem. ?he post-quarts: movement may be relatedtofaulting. Muller (1980) haspostulated a Shawnigan fault extendingalong MacdonaldLake Valley and underSooke Lake, offset.ting a postulatedSurvey muntain fault whichjuxtaposes Ieech Riwr (and Malahat)rocks against Colquitz gneiss. However, asalready noted, the Malahatschists pass gradationally into the Colquitz. Any fault in this part ofthe area would have topass southwest of the schists and the sedimentarybeds immediately underlying them, and wou'Ld therefore lie withinthe LeechRiver Formation. Any movement under Macdonald Valley wouldhave to be slightas the units appear to matchup ,across it.

43 Three small faults are inferred to underlieMartins Gulch (Fig. 15). The northone is indicated by right hand offset ofthe contacts of unit 100, andnortherly deviations in the strikes of beds can be attributed to drag on thisfault. Attitudes in the vicinityhave argillite of unit 75 strikinginto quartzite of unit 76; a fault is postulated to separate them. Movement would have to be left hand, as unit 74 is toothin to be thecontinuation of 76. A small fault in unit 71 is indicated by right handoffset of two fairlydistinctive beds, represented by bedding symbolswith 80-degree dips.. An opencrack in units 71 and 72 locally containsmylonite, but no offsetcould be detected. There are doubtless other small cross-faults in the area, whichcould be detectedwith good exposureand detailed mapping.

AGEAND CORRELATION

No radiometricages have been obtainedfrom the present area. The nearestdated samples (Wanless, et dl., 1978) are from800 metres southwestof West Leech Falls;actinolite schist yielded a K/Ar ageof 41.122.8 Ma and sills intruding it an age of36.722.6 Ma. The actinolite represents a much higher grade of metmorphism than is found in the present area, andevidently was produced by a Tertiarymetamorphic event peneconternporaneouswith intrusion. A minimum agefor the Leech River Formation is imposed by thefact that theoverlying Malahat schists must pre-datethe Colquitz. Muller (1980) quotes K/Ar datesfor the Colquitz rangingfrom 131 to 182 Ma. The Malahatand Leech River must therefore beof Eonanza ageorolder. Of thevarious formations on Vancouver Island,they most nearly resemble theSicker Group. Unit 100 closely resembles a common typeof Sicker volcanicrock. lbe Sicker sedimentary bedsexposed in Chemainus River are somewhat thickerthan the thin Leech Riverbeds, but their lithology is similar andthey have been folded in a similar way. The volcanic-sedimentarysequence appears tobe reversed, and it is suggestedthat the Malahat and MechRiver together are correlativewith Sicker volcanic rocks, thesediments accumulating distallyto continued volcanism in the Sicker type area. Recentusage by Mullerand others has been to include the Malahat in the Leech River, but it is much thickerthan the volcanic units within the Leech River and appearsto overlie it disconformably,therefore it is usefulto retain it as a separateformation.

ECONOMIC GE0UX;Y

The writer was shown nuggetand fine gold recovered from the gravels in MartinsGulch, but no visiblegold was found inthe bedrock. A small proportion of the numerous quartzveins inMartins Gulch and inthe tunnelcontained appreciable pyrite. of ninepyritic veins sampled, only onecontained gold or silver above the detection limit, and it had only 0.3 ppn gold.Shear and gouge zones appeared barren.

44 In the spillway of SookeLake dam, underthe bridge and for some di.stance above, theMalahat schistscontain disseminatedchalcopyrite and bornite. This is evidently a localizedzone, as mineralization was notfound in road and railwaycuts. However, theschists pass out of thewaters:hed a short distance east of theCanadian National Railway line, and prospectingthere for similar zones is warranted.

REFERWCES

Clapp, C. H. (1917): Sookeand IXlncan Map-Areas, Vancouver Island, Geol. Surv., Canada, Mem. 96, pp. 366-368. Eastwood, G.E.P. (1982):Leech River Area, Vancouv

45 A radiometricage was obtained in 1982 thatrequires revision of the conceptof the Sicker Group. The geologyof the Mount Richardsarea is shown on British ColumbiaMinistry hergy,of MinesandPetroleum ResourcesPreliminary Map 40 anddescribed in GeologicalFieldwork, 1979. Briefly,Sicker volcanic and less sedimentaryrocks are intruded by large dykesand irregular stocks gabbro-likeof shonkinite. This is the gabbro-dioriteofClapp (1917) and evidentlythe diabase of Muller's (1980a. 198Ob) sediment-sillunit. A QWac MineralsLimited diamond- drillhole, drilled in orabout 1972, passed through part of the dyke north of Ereen Lake,and thewriter logged and sampled the core. A hornblendeseparate was made andsubmitted to the University of British Columbia for K/Ar determination. J. Harakalreported an age of 363+13 Ma andcommented thatthe material was of superbquality.

The Sicker rocks have been traced into the typearea on Big Sicker Mountain,where they are similarly intruded by shonkinite.Schist belts were developed in the Sickerrocks prior to intrusion. mus thetype Sicker is MiddleDevonian and/or older. The Buttle Zake limestonehas beendated paleontologically as MiddlePennsylvanian OK possiblyEarly Permian.%us it and otherPaleozoic deposits that postdate the deformation and intrusionare not Sicker. It is thereforepossible that the hostrocks of Westmin ResourcesLimited's Buttle Zake massivesulphide depositsare not Sicker.

REPKRERCES

Clapp, C. H. (1917):Sooke and IXlncan Map-Areas,Vancouver Island, British Columbia,with Sections on theSicker Series and theGabbros of Qst Sookeand Rocky Point hy H. C. Cooke, Geol. Surv., Gnada, Mem. 96,pp. 125-172, nap 42A. Eastwood, G.E.P. (1980a):Sicker Project - Mount Richards Area, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1979, Paper 1980-1,pp. 49-51...... (1980b): Geologyof the Mount Richards Area, B.C. Ministry of Energy,Mines & Pet. Res., Prelim. Map 40...... (1982) : Geologyof theWhitehouse Creek Area, B.C. Ministry of Energy,Mines S Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1,pp. 78-83. Muller, J. E. (1980a) : %e PaleozoicSicker Group of VancouverIsland, British Columbia, Geol. mrv., Canada, Paper 79-30...... (198Ob) : Geology Victoria Map Area, Geol. Surv., Canada, Open Open File 701.

46 GEOLOGY AND GRAVITY SURVEY OF THE TWJMFXN COAL BASIN (92H) By B. la. Church and D. Brasnett

INTFCODUCTION

Thisreport reviews the coal depositand host rocks of the TUlameen basin inthe light of new geological and geophysicaldata. The new information includespetrological and age determinations, and a gravitysurvey that givesinsight into the structure of thebasin.

HISTORY

Coal was discoverednear Blakeburn Creek in the TUlameen basinprior to 1900.In 1904 control of thedeposit was secured by 8.13. Coal and Coke Co. andthis was soonfollowed by large-scale exploration. Work commenced simultanecuslyon the northeast side of the basin on Collins Gulch andnear Blakeburn Creek to thescuth. Activity continued over the next 30years with the development of five undergrcund mines in the Blakeburn area.

In1913 Coalmont Collieries Ltd. gainedcontrol and initiated work at mine Nos. 1 and 2. An aerial tramway was constructed 1.n 1920 tcl carry the coal fromthe minesite to therailway at Coalmont where it couldbe processed and readilytransported to markets. Mines Ncj. 3 and 4; began operationsinthe mid-l920's, however, floods and firescaused their eventualclosures in the mid-1930's. The last operating mine, No. 5, openedin 1931 andproduced for nineyears. In 24 years of operation 2 144657 tonnes of coal were shippedfrom 'Iulameen Codfield.In the years 1954 to 1957, mllin's Strip Mine Ltd. operated ,st Blakeburn, at the site of some of theold underground workings, producing 148 239 tonnes of coal. Imperial Metals & Power Ltd. continuedactive explorationin the 1960's with rmch trenchingin the northwest part of the basin. Cyprus AnvilMining Corporation continued this work: plus additional diamond drillingin 1977and 1978 underoption agreement.

GmLOGICALSETTING

The'Iulameen basin,centred 2 kilometres west of Coalmont, is a Tertiary outlier with an elliptical northwest-southeastelongated sedimentary core measuring 5.4 kilometresby 3.6 kilometres(Fig. 16). 'Lhe geology of the basinhas been previously described by Camsell (1913), Rice (1947), Shaw (1952), andEvans (1978)and examined inspecific aspects by Hil.ls, et dl. (1967),Donaldson (1973). and Peavers, et al. (1980).

Eocenevolcanic and sedimentary rocks rest unconformably on Triassic greenstones andmetasedimentary rocks. They are overlain by Miocene basaltlavas and breccias.

41 \ / \

Figure 16. &olog ofthe Tularmen basln. (See Fig. 18 tor legend.)

TABLE 1. CHEMICAL ANALYSIS OF VOLCANIC ROO(S OF THETULAMEEN BASIN

Oxldes recalculated to 100% Ox1 des as determl ned 1 2 i 2 SI 02 68.61 8921 Hzo+ 0.85 3.80 TI 02 0.45 0.1 1 Hzo- 1.23 3.18 15.98 A I2'3 1663 co2 0.70 1.39 Fe203 2.59 0.01 'Z05 0.28

Key to Analyses: 1 = Hornblendedaclte ot Cedar volcanlc rocks trom road cut on south slope ot Ham1 lion Hi I I. 2 = Fhpllie tutt band near top ot coalrmasures In Blaaburn pit.

48 me Eocenebeds areestimated to be 800 metresthick where best developed. The coalmeasures, about 30 metresthick IBlakeburn), are sandwichedbetween 200 metres of sandstone and shalebelow, and 60 metres of fissile shalesabove (Collins Gulch section). An estimatedthickness of 500 metres of quartzosesandstone and conglomerate Eorns the uppermost part ofthe sedimentary succession in thecentral part of the basin.

TheEocene volcanicrocks, named 'Cedarvolcanic series' by (amsell (1913), arepartly intercalated with the basal sedimentary units. The volcanicseries attains a thickness of about 500 metres 'on Hamilton Hill and Mount Jackson,where the typical rock is lightgrey dacite with small hornblendeneedles (see analysis No. 1, Tsble 1). However, arcfusion analyses of 51 lavasamples show a full range in compositions from basalt torhyolite (Fig. 17). mefrequency of felsic volcanic rocks increases stratigraphically upward to where rhyoliteash forms 12 separate bands in theupper part of tnecoal measures (see analysis No. 2, Table 1).

51 &N&L"ZEZ

RErRAcTIYt INDEX OF GLASS

RHIOLITE I DltCITE I ANOESITE I BltSitLT

Figure 17. Retractiveindex frequency plot for the Eocene volcanic ro&s ot the Tu Iamen bas I n.

The age of theserocks is placed nearthe boundary between Lower and Middle Eocene,based on the recent determination of a sample of amphibole submittedto J. Farakalat theUniversity of Brirish Columbia. 'fiisis comparableto previous K/Ar results on bedsassociated with the Pr.inceton and Hat Creek coaldeposits (see Table 2).

TABLE 2. RAD ICMETKiC AGE UETERMiNATiONS OF EOCENECOAL MEPSURES, SOUTKCENTRAL BRITISH COLlMBiA

No. Rock MI nera I North West K ~r*40 Ar*40 Age Sou rce Lot. Source bng. % cc/gm Z (Ma) 1 Cedardaciteanphibole 49'30.2' 120046' 0.761 1.469 756 49.0t1.7 2 Rincetonash biotite 49'27.4' 120'32t 6.76 1.3149.222 84 3 Hat CrecA rhyolitebiotite 50040.5'121'34.5' 6.87 l.3!) 90 51.221.4

1.b. 1 = thisstudy, No. 2 = Mathmvs (1964, p. 4651,and No.3 = Church(1975, p. G1,O) corrected according to tho wthod ot Steiger andJager (1977).

49 n LODESTONESECTION B

BLAKEBURNSECTION C 2 D

1000

wIn E 500 z

0 METRES

0 1600 3200 Y6 - - 4 5!-. .. e,.... .*-. x\.. ..I - ‘?, 43: ““..‘...~~~bc!.,,0, ...’.... GW]f .. . ,*o‘..: . ::: ..... *...... * - Q 0-

LEGEND

M IOCEN E EOCENE MIOCENE /CONTINUED1 P P 3.O BASALT 2.2 SHALE AND SANDSTONE

EOCENE 2.2/2.6 TEPHRA/ANDESITEVOLCANICS. CEDAR

2.5 Ip] SANDSTONEBASEMENT ROCKS

2.2GREENSTONE 2.8 SHALE AND CRYSTALLINE ROCKS

1.4 COAL DENSITY = p

Figure 18. Geologicalcross-sections and gravity profi 18s of the TuIameen Basln. (Refer toFlg. 16 tor posltlon of sections.)

50 Miocene basalt(dated 9.020.9 Ma by Evans, 1978) are dp to abolt 100 metres thick. These lavaflows unconformably overlie the Dcene sedimentaryrocks in thesouthern and west-central part of the? basin. F'eeder dykesto the basalt flows cut olderrocks in thearea, inchdin'? coal bedsnorth ofBlakeburn pit. Here a large dykeabout 50 metres wide intrudesthe fault zoneand divides the old mine workings.

GRAVITY SURVEY

A gravitysurvey conducted by Brasnett(1981), on behalf of the Ministry,facilitates preparation of structural cross-sections of the basin. A synthesis of two cross-sections shown on Figure 18 is basedon total gravityresponse in terms ofthickness and densit:ies (P) of' major stratigraphic units.

A LaCoste-Romberg gravity meter was employed inthe survey and operated according to manual specifications.Readings wereperformed at 50-metre intervals at topographicstations established by Ager,Beret'ta and Associates Ltd.

The northline ofthe survey proceeds 5.1 kilometres aon course of approximately 060 degreesfrom 'A,' at the western marginof the basin on theLadestone Mountain road, and ends at 'B' nearthe Bear's Cen coal prospect on the east side(Fig. 18). The main features seen :tn this sectionare gentle-dipping beds (maximum dip ofabout 35 degrees), a down-faulted eastern margin,and westerly thickening stratigraphic units. The axialplane of this elongated basin is inclinedwith a keeldisplaced more than 1 kilometrewesterly from theaxial trace as seen insurface plan (see Evans,1978, p. 84).

The southline follows an old tramway 3.2 kilometres on a courseof 045 degreesfrom Blakeburn pit. Notably, this section shows a Miocene basalt cap on a relativelythin andgently dipping Eocenesequence. me keel of the basin on this line is roughly450 metres higher i:? elevationthan onthe north line, which is closer to the centre of thebasin. This indicatesthat the overall structure is notsimply a southeasterly plungingsyncline as suggested by Evans.

Insmmary, the evidence suggests that the basin developed as a drainage trapaccumulating first sandstone, then shales and coal whichthickened westerlyagainst the still active Cedarvolcanic pile. A final in.Eluxof quartzosesand and conglomerate completed an infillcycle following a late episodeof rhyolite volcanism and subsidence. Preservation oE these strata from erosion was effected by normal faulting on the ea.st and southeastmargins of thepresent Eocene outlier and extrusion of,capping Miocene basaltlavas.

51 THE COAL DEPOSIT

Drilling by Cyprus AnvilMining Corporation in the northwest part of the sedimentarybasin shows thatcoal may occuranywhere in theshale facies. According to Shaw (1952),the lowest coal seam is about120 metres above the Cedarlavas and breccias and 40 metresbelow the principal coal measures. Shaw alsoreported coal in the upperquartzose sandstone- conglomerate unit.

The thickest andmost continuous coal deposit is in theBlakeburn area whereDonaldson (1973) described in detail a 27-metre sectionof coal at the site of the oldmining operation. The originalmining excavation followed a 2 to4-metre-thick seam with a strikelength of 2.3 kilometres. The coal is a highvolatile bituminous B and C variety,having 2 to 5 percent moisture content, 4 to 16 percent ash, 0.3 percent sulphur,and yielding about 3 000 kilogramcalories. The usualbright character of thecoal is due tohigh vitrinite conposition. Reflectance measurements on thevitrinite (Ao) rangefrom 0.79 to 0.94,showing a generalincrease downward (see Table 3 andDonaldson, 1973, p. 8). Individual seamsabove and below the mineseam areseparated by clay layers,rhyolite ash bands, or shaly partings.

TABLE3. VARIATION OF VlTRlNlTE REFLECTANCE (Ro) THROUGH THE BLMEWRN COALMEASURES

Igtres below kt lectance top ot coal RO measures

0.3 0.804 0.3 I. 0 0.831 2.0 0.846 2.7 0.822 4.2 0.790 8.0 0.847 11.0 0.843 13.0 0.928 17.0 0.884 20.0 0.944

Laterallythe coal beds 'shale cut' as is typical of limnicdeposits. The main coalzone has been traced 3 to 4 kilometresalong strike northwest fromthe Blakeburn pit to wherethe measures are 15 to 20 metres thick. However, tothe east andsouth the coal horizon diminishes to a few thin seams at Collins CXllch andimpure carbonaceous beds at the Bear's Den and Hayes-Vittoni prospects.

According toPeavers, et dl. (1980),the high vitrinite content of the coalsuggests a woody scurceand probable forest-moor origin. Stagnant acidconditions converted mch of the interbeddedrhyolite ash to kaolinite. The regularityof alteration textures and thecontinuity of

52 these ashbands suggests a quiet, low detrital transport domain.The local clastic character of the coal is tectonic, resulting frombedding planefaulting related to concentric folding. Such movements art? most prominent in deepersections of thebasin and i.n steeplydipping segments near the east margin.

Theunexpected high rank of thecoal is apparentlydue to a highgeo- thermalgradient, ascribed to EOcene volcanism inthe reqion. Donaldson (1973, p. 9)discounts any contactmetamorphic effect from the overlying Miocene basalt. The general downward increase in thereflectance of vitrinite seems to be a function ofdepth of burial. Peavers, 1st al. (1980)determined the relation between reflectance %, pateotemperaturos, and time. Accordingly,observed reflectance values would result from a minimum paleotemperature of 75 degreesCelsius for a periodof 50 million yearsor a more reasonableestimate of 130 deqrees Celsius for 10 million years.

CONCLUSIONS

The 'IUlameen basin is a faultedelliptical structure of possiblevolcano- tectonicorigin. New radiometricdeterminations give an Eoceneage comparable toprevious K/Ar results from othermajor 1imn:ic coaldeposits ofthe southern interior region such as in the Hat Creekand Princeton areas.

A gravitysurvey gives a profile of the Tertiary formations,delineAting thebasal volcanic andsedimentary rocks and coal mea:;ures. The 800 metres of stratacomprising the basin record a history of earlyvolcanic eruptioncausing disruption of drainagepatterns, stagnation leading to sedimentationand coal formation, and finally infilling by coarsesand- stonesand conglomerates. Preservation of these rock:; resulted from normalfaulting, folding, and extrusion ofyoung basaltlavas.

Rhyoliteash bands concentrated in theupper part of the coalmeasures may reflect a resurgentvolcanic event associated with high geothermal gradients.Evidence suggests that anomalous Eocene geothermalgradients areresponsible for the comparatively high rank of thecoal.

REFERENCES

Adamson, T. J. (1978): TulameenCoal Project, Cyprtis AnvilYining Corporation, Assessment Rept.77-(1)A. Brasnett, D. (1981) : The nllameen and Colwood GravitySurveys, Univ- versitq of Victoria, Co-op WorkTerm Rept., 26 pp. Camsell, C. (1913):Geology and MineralDeposits of thenlameen District, BritishColumbia, Ceol. .%rv.,Canada, Mem,, 26, 98 pp. Church, B. N. (1975):Geology of the Hat CreekCoal Basin, B.C. Ministry of Energy,Mines & Pet. Res., Geology,pp. G99-Gl18.

53 Donaldson, J. R. (1973): 'Ihe Petrography of the Coal from the Blakeburn Strip Mine in the TulameenCoal Area, British Columbia, Geol. Surv., Canada,Paper 72-39, 13 pp. mans, S. H. (1978): TulameenCoal Basin, B.C. Ministry of Energy, Mines S Pet. Res., GeologicalFieldwork, 1977, Paper 1978-1, pp. 83,84. Hills, L. V. andBaadsgaard, H. (1967) : Potassium-ArgonDating of Some Lower TertiaryStrata in British Columbia, Cdn. Pet. Geol., Bull., VOl. 15, NO. 2, pp. 138-149. Mathews, W. H. (1964) : Potassium-Argon Age Determinations of Cenozoic Volcanic Rocks from British Columbia, Geol. SOC. Am., Bull., Vol. 75, pp. 465-460. Peavers, D. R., Williams, V. E., andMustoe, G. E. (1980):Kaolinite, Smectite,and K-Rectorite in Bentonites: Relationto Coal Rank at Tulameen, BritishColumbia, unpub. manu., 28 pp. Rice. H.M.A. (1947): Geology andMineral Deposits of thePrinceton Map- mea, British Columbia, Geol. Surv., Canada, Mem. 243,136 pp. Shaw, W. S. (1952) : me 'Ihlameen Coalfield,British Columbia, Geol. Surv., Canada,Paper 52-19, 13pp. Steiqer, R. H. andJaqer, E. (1977) : SubcommisiononGeochronology: Convention of the Use of Decay Constantsin Geo andCosmochronology, Earthand Planet. Sci. Lett.,Vol. 36, pp. 359-367.

54 THE NAGYGOLD OCCURRENCES, WCTORS POINT, EARRISON LAKE (92H/1 ZW)

By G. E. Ray

INTRODUCTION

Duringthe summers of 1981and 1982, theauthor briefly examined. gold occurrencessituated near bctors Point, which is on the west si.de of Harrison Lake approximately 45 kilometres north-northeast of Harrison Hot Springs. me property is reachedvia an unpavedroad passing north from WeaverCreek EYovincial Park. The occurrences were discovered by a prospector, George Nagy, andhave been tested by trenching and some recentdrilling. lhe No. I occurrence lies closeto the 1.akeshox-e at the northend of Doctors Bay approximately 150 metres north c,€ GeoryeIWgy's cabin(Fig. 20). The No. I1 occurrence is seen in a quarriedexposure alongsidethe road, about 300 metres southwestof the cabin. lhis write- upbriefly describes the geologic setting and mineralizationobserved in thetrenches and reports some gold-silverassays and trace element analyses of mineralizedgrab samples collected by theauthor,

GENERAL GEOmY

The regionalgeology, adapted after compilations by Roddick(1965) and Monger (1970), is shown on Figure19.Major, southeasterly trending fracturespassing along Harrison Iakeare associated with regional hot springactivity and separatethe highly contrasting geological regimes exposed on thenortheastern andsouthwestern shores of the lake. The Nagy gold occurrences lie close to this fracturesystem and also close to theintrusive contact between a youngerquartz diorite bodyand hornfel- sedcountry rocks that are of uncertainage and origin. Further west, Roddick(1965) assigns rocks correlative with the country rocks ':a the Jurassic orCretaceous Fire LakeGroup (Fig.19); Monger's (1970) c8mpi1- ationassigns the countryrocks of the occurrences to the Middle Jurassic Mysterious Creek Formation.

GEOLOGY OF NO. I OCCURRENCE

A 7-metre by 7-metre excavatedtrench exposes a ver:?fine-gr,3ined, massivetextured, dark to medium greyhornfels. This rock is cut by prominentjointing or fracturecleavage. Fractures are 2.5 t.o 7.5 centimetres apart;they strike 170degrees and dip 45 degrees wes':. In thinsection the hornfels has a marked decussatetexture. Unt*rinned plagioclaseand quartz crystals generally range between 0.05 t.0 0.1 millimetre in diameter but some remnantplagioclase cry!jtals are up to 0.25 millimetres. These largerfeldspars have recrystallized i~nto a Fine, polygonalmosaic of smallcrystals. Biotite forms minute (less than 0.1-millimetre), randomly orientated,subhedral laths andcomprise

55 Flgre 19. Regional geoiog ofthe DoctorsPoint area, Harrison Lake. (Ceology adaptedafter Monger, 1970).

SYMBOLS am...... _,"

,NTOUR...... J- >ST"LAIEO FAULT ...... // TENCH WIT" GOLD MlNERALlZATlON . . x A"

Figure 20. Locationof the Nagy goldoccurrences, lbctors Point,Harrlson Lake.

56 up to 10 per cent of thetotal rock. Wcessory minerals j-nclude epidote, zoisite,clinozoisite, sericite, chlorite,muscovite, an3 opaques., The muscoviteoccurs as late, ragged,poikiloblastic crystals with many inclusions; it may beintergrown with biotite. The opaques form less than 1 per cent of thetotal rock. They arelargely nunute magnetite granulesbut there are minoramounts of pyrite. In cutcrop numerous randomlyorientated sulphide-rich veins cross the hornfels. Most are less than 2 centimetres wide but some are up to 12.5 centimetres in width. mese veinscontain massive pyrite and arsenopyrite with lesser amountsof limonite, jarosite, scorodite (FeAs04'2H20), sericite, quartz, andchlorite. Less commonly, thinner(generally less th.an 1 centimetre wide)quartz veins cut the hornfels. Some quartzveins contain central vugslined with small euhedralquartz crystals.

Gold and silverassays and trace elementanalyses from grabsamples of sulphidevein material from the No. I occurrence are shown in 'E'ble 1. The gold-silvermineralization is associatedwith anomalous amou!ntsof bismuth,cobalt, copper, mercury, molybdenum, tungsten,lead,and arsenic.

TABLE 1. TRACEELEMENT ANALYTICAL RESULTSFRCM MINERALIZED GRAB SAWLES FROM THE NO. I NAGYCCCCRRENCE

GR 40 GR 210 GR 211 Au* 0.7 ppm 5.4 ppm 5.8 ppm As * 8 Ppm 6.2 ppm 40.9 ppn As* 0.35% BI" 56 PW CO" 11 PPm cu* 0. I51 F** 178 ppm t!g*** 280 ppb Mo* 10 PPm Sb" <5 Ppm W*"* 26 ppm Pb* 56 PW Nif 6 PP~ Zn* 165ppm

*mom1 c absorpt Ion **Ion specific electrode '**Coldvapour AA ***Tolwrlmtrlc

G3 40 - tbrnfels with sulphlde velns up to 5 centlmetres wlds, collected from swth end of trench.

GR 210 - tbrnfels with thin sulphlde velns and vuggy quartz veins, col lected from north end of trench.

GR 211 - tbsslve pyrlteersenopyrlte from lZ-=entlmetrerlde sulphlde vein, collected from south end of trench.

51 GEOLOGY OF NO. I1 OCCURRENCE

The No. I1 occurrence is seen in a quarriedexposure on the east side of the main access road,approximately 50 metres northof the turnoff to Doctors my (Fig.20). Mineralization is localizedalong the faulted contactbetween a quartz diorite tothe north and structurallyunderlying fine-grained,massive grey hornfelsic rocks to the south.

The mineralizedzone, which is up to 0.7 metres wideand exposed for 20 metres alongstrike, trends 130 degreesand dips gently (20 to 30 derjrees)northward parallel to the faulted margin of the overlying quartz diorite.Mineralization consists mainly of coarsepyrite andarseno- pyritewith abundant light green scorodite (FeAs04'2H20). In addition, the zone carries limonite,quartz, sericite, and feldspar. Locallythe mineralization is rhythmicallyzoned and vuggy while elsewherethe sulphideshave been extensively leached, producing a pronounced boxwork texture. Remnant coarsecrystals of quartzand altered feldspar in these leached areas resemblethose in the hangingwall quartz diorite.

Minornormal faults andnumerous small fracturesstriking 160 degreesand dipping 75 degreeseast cut anddisplace the main mineralizedzone. %in mineralizedveins in these youngerfractures, suggest some late stage remobilizationof the sulphides. Gold and silver assaysand trace elementanalyses of sulphide-richgrab samples from the mineralized zone are shown inTable 2.

TABLE2.TRACE ELEMENT ANALYTICALRESULTS FROM MINERALIZED GRABSAM'LES FRCM THE NO. II NAGYOCCURRENCE

GR 213 GR 215 Au* 19.9 ppm 34.6 ppm Ag" IC469 ppn 1126 ppm AS'" >3% >3% Bi** Tr Tr Mo* Tr Tr W** Tr Tr Sb** 0.02% 0.02%

"Rtomlc absorption **Ssmlquantltatlve emission spectroscopy

GR 213 - Sulphide-rich grab sample from northern exposed portion of mineral lzed zone.

GR 215 - Sulphide-rich grab sample from southern exposed portion of mi nera i i zed zone.

58 Both in hand specimen and thin section thefootwall hornfels closely resembles the hornfels that hosts the No. I occurrence. However, at the No. I1 occurrencethey are coarser grained(up to 0.3 nliilimetre:;) and containappreciably more sericite, magnetite,and other opaque min'erals; the coarser texturepresumably reflects its closer proximity to the quartzdiorite pluton. Recognition ofvague, remnant clasts underthin sectionsuggests that the hornfels is eitherthermally metamorphose'3 tuff or clastic sedimentaryrock.

The hangingwallquartz diorite is a massive,coarse-grained rock with crystalsvarying from 2 to 10 millimetres in diameter. It consists of 15 to 20 per cent hornblendewhich forms subeuhedral prisms and commonly enclosesremnant, corroded augitic cores. Biotite forms 1 to 3 percent ofthe rock; some is intergrownwith the hornblende. It is partially altered to chlorite. The plagioclase (An30-47) formswell-twinned, zonedcrystals with clouded cores and clear marglns; many are partially saussuritized.plartz makesup 1 to 3 percent of therock, and sub- euhedralpyrite crystals are recognizablein hand specimen.

The quartzdiorite generally has a fresh, homogeneous appearancebut immediatelyadjacent to its faultedcontact with the hornfels it is leachedand highly fractured. In a highwayexposure on the hairpin bend approximately 1.2 kilometresnorth-northwest of the No. I1 occurrence, numeroussubhorizontal, 7 to 10-centimetre-wideveins of leucocratic biotitequartz diorite cut the pluton. At thislocality 11 steep westerly dipping,north-south-trending fault zone cuts the body. :Intensefractur- ing and alterationover a 5-metrewidth marks thisfault. Gently plungingslickensides (23degrees toward 200 degrees)suggest: some subhorizontal movement.

DISCUSSION

The two most likelyexplanations concerning the controls and origin of the Nagy goldoccurrences are:

(1) The mineralization was geneticallyrelated to thequartz diorite intrusion,which explains its spatial associa.tionwith the hornfelsedmargin. Ifcorrect, this suggests that theremaining marginofthe quartz diorite body and possiblythose of other granitoidplutons in the area, particularly wherethey intru'3e the Fire lake orHarrison lake Groups(Fig. 21), may represent good explorationtargets for similar gold-silverminera1i:zation.

(2)Mineralization was preferentially emplaced alongthe faulted pluton marginduring hydrothermal activity which was notnecessarily relatedto the quartz diorite intrusion. The Nagy occurrences lie closeto a regionalfracture system that is assomziated with one formergold producer (Providence, MI 92H/NW-30), nml?rousother gold occurrences,and regional hot spring activity (Fig. 21). nus, the

59 HarrisonIake fault system, particularly its northernsection where it intersects bothgranitic plutons and theFire LakeGroup, could representan interesting exploration target for bothhigher tempera- turevein and epitherrnal, Cinola-type gold mineralization.

Figure 21. Regionalgeology ot theMrrison Lake fault systemshouing hot spring andgold occurrences. IGeoIoq adaptedatter Roddle (1965) andMonger (1970) I.

60 AcKNmpDGElwlTs

Thanks are extendedto George Nagy ofNagyville Mining Ltd. for his assistanceand cooperation. Dr. J. Kwong assistedwith some X-ray identifications.

REPERENCES

Monger, J.W.H. (1970): HopeMap-Area, West Half (92H w 1/2),Eritish Columbia, Geol. mrv., Canada, Paper 69-47, 75 pp. Roddick, J. A. (1965) : VancouverNorth, Bquitlam and Pitt Lake Map- Areas, British Columbia, Geol. Surv., Canada, Mem. 335, 276pp.

61 Flgure 22. Reglonalsetting of theCoqulhalla gold belt shwlng locatlon of golddeposits and occurrences. (GBology adaptedatter Monger, 1970).

62 CAROLINMINE - COQUIHALLA GOLD BELT PROJECT (928/6, 11)

By G. E. Ray

INTRODUCTION

The secondseason of fieldwork studying the geology and mineralization of theCoquihalla gold belt was carriedout by a two-man field crew. The areastudied in 1982 is situatedapproximately 20 to 25 kilometresnortheast of Hope. "his work includedthe following:

Regionalgeological mapping (scale 1:50 000) of thebelt from Mount Snider in thesouth northward toward Siwash Creek. A thirdfield season's work shouldcomplete the regional geological. mapping of the goldbelt northward to the vicinity of Chapmans Bar.

Geologicalmapping, at a scale of 1:6000, ofan area between :Spider Peakand theCoquihalla River. "his area contains mostof thegold occurrences in thebelt, many of thepast gold producers, such as theEmancipation, Aurum, and Pipestem,aswell as the presently operatingCarolin mine.

Cetailedsurface geological mapping (scale 1:500) averthe Eormer Pipestemgold mine (MI 92H/NW-11), togetherwith underground mapping andsampling (scale 1:250) of the lower,most extensive (No. 4) level of theold Pipestem mine workings.

Surfacegeological mappingand sampling of the 'McMaster zone'gold mineralization,situated approximately 0.5 kilometressoutheast of McMaster pond.

Samplingthe HOme X goldoccurrence (MI 92H/NW-13) and the newly discovered 'Murphy occurrence.'

Collection of approximately 80 silt samplesfrom $itreams draining thebelt. These are being assayed for gold, arsenic, chromium, copper,mercury, nickel, lead, antimony, zinc, and cobalt, anc3 this data will beused in conjunctionwith the results of the 1981 RegionalGeochemical Survey (RGS 7) determineto whether any regionalgeochemical patterns are associated with mineralization in thebelt.

RBZIONAL GEOLOGY

Gold occurrences in the Coquihallagold belt are regicumlly clustered closeto the eastern margin of theCoquihalla serpentine belt (Fig. 22). Thisserpentine belt formsan elongate,north-northwesterly trending, steeplydipping unit separating supracrustal rocks of theLadner Group in

63 the east from the HOzameen Group inthe west (Fig.22). lhe serpentine belt reaches its maximum development in theCarolin mine-Coquihalla River area where it exceeds 2 kilometresin width. It graduallynarrows to the southand north until in the Poston Par andManning Park areas (Monger, 1970; mates, 1974;Cardinal, 1982) the Hozameen andLadner Groups are in directfault contact. Dark,highly sheared tomassive serpentinite of probableperidotite parentage (Cairnes, 1929;Table 5) characterizes the beltbut it also containssubstantial amounts ofhighly altered gabbro- diabaserocks (Table 7).

The easternmargin of the serpentine belt is sharplydelineated by the Hozameen fault which,due to its close spatial associationwith many gold occurrences,has been mapped andstudied in some detail(Cairnes, 1924, 1929;Cochrane, et dl., 1974;Anderson, 1976; Cardinal, 1981, 1982; Ray, 1982;Wright, et dl., 1982).In contrast, the western maryinof the serpentinebelt has previously been largely ignored. However, current map- pingsuggests it toorepresents a major fracture, which like its eastern counterpart,has had a longand complex history of both vertical and horizontal movements. The eastern boundary fracture is hereintermed 'East Hozameen fault;'the hitherto unnamed western tectonicboundary is calledthe 'West Hozameen fault.' With thegradual disappearance of the serpentine belt bothnorth andsouth, these boundary fractures merge into a singletectonic feature, the HOzameen fault(Fig. 22).

Themzameen Group consistslargely of cherts, pelites, and altered spiliticbasalts (Daly, 1912; Qirnes, 1924;WTaggart andlhompson, 1967;mnger, 1970). Monger (1975)interprets this as oceanican supracrustalsequence of Triassic or pre-Triassic age.In the map-area the Hozameen Rouprocks have been subjected to lowergreenschist metamorphismand strong deformation; some parts are overprinted by either a schistosity or an intense,subhorizontal mullion structure. Close to theserpentine belt, Hozameen Group rocks commonly show signs of increaseddeformation and crushing, minor silicification, late brittle faulting, andpronounced slickensiding. me West Hozameen fault appears todip steeply east, and serpentinites inthe immediatevicinity contain highlysheared talcose rocks and, rarein instances, poor quality nephrite.

The Iadner Group (Cairnes,1924) comprises a sequenceof fine-grained, poorly to well-bedded slatyargillites and siltstones withminor amounts ofcoarser grained material. mese metasedimentaryrocks have a weak to intenseslaty cleavage and were subjectedto at least threeperiods of regionalfolding (Table 1). Despite this,Iadner Group rocksgive an overallimpression of being less deformedthan the Hozameen Group,and a widevariety of sedimentarystructures are commonly preserved(Ray, 1982).Regional folding has resulted in widespread structural repetition and many sections of theIadner Group adjacenttothe Bquihalla serpentinebelt, including those hosting the gold mineralization at Carolin mine (Idahozone), are structurallyinverted (Table 1). Cairnes (1924)considered the thickness of theIadner Group in theBquihalla

64 River-LadnerCreek area to beapproximately 2 000 metres, butrecognition of widespreadstructural repetition suggests its truethickness may be considerably less.

The broadstratigraphic sequence recognized within the Ladner Group in theCarolin mine-Ladner meekarea (Ray, 1982) continuesfurther north intothe vicinity of thePipestem mine (Fig. 23). The LadnerGroup rests either unconformablyor disconformably upon anolder volcimic greenstone; its lowermost stratigraphic portion consists of a thin,heterogeneous assortment of coarseclastic, partly volcanogenic sedimer,tary rock:; that pass upward into a thickersequence of well-bedded siltstones. These are overlainin turn by a thickunit ofcarbon and iron-rich argillites. lbe lower clastic unit which hoststhe Carolin gold mineralization (Idaho zone)comprises discontinuous wedgesof interbeddedgreywacke, lithic wacke,conglomerate, and possible reworked tuff with int.ercalated units ofargillite andvolcanogenic siltstone. The basalportion also includes rare, thinhorizons of clastic, impurelimestone. The conglomerates containangular to well-rounded clasts; most are of volcanic orig:Ln but there are minoramounts of quartz,jasper, chert, limestone, granit,?,and gabbroic material. While mostof the volcanicpebbles xe identicalto theunderlying greenstone unit,clasts ofrecrystallizemi, altered porphyritic andnonporphyritic flow-layereddacites are 1ocal.ly common.

The economicallyimportant lower clastic unit shows gre,atvariatj-on in thicknessalong the belt. In most parts it is eitherthin or absent; for example,near the Rnancipation mine it is less than 5 metres thick,while inthe vicinity of Carolin mine(Ray, 1982) it is approximately 200 metres thick.

The LadnerGroup stratigraphicallyoverlies older greenstones which are traceablediscontinuously for more than 15 kilometresalong the eastern side of the Fast Hozameen fault(Fig. 23); in many places it structurally overliestheLadner Group.The greenstone-Ladner Group contact is commonly marked by faulting andshearing, but in places the sedimentary rocks rest directly on the volcanicrocks with either an unconformable or a disconformablerelationship. A local basalconglomer,nte of variable thicknesscontains abundant clasts of material clearlyderived from the underlyinggreenstones. Refractive index determinations on fusedglass beadsand chemical analyses (Table 6) indicatethat the greenstones are highlyaltered andesitic to basaltic volcanic rocks. Ihe greenstones are fineto medium grained and are generallycharacterized by theirmassive, homogeneous appearance; some specimens containrandomly orientated, late crystals of stilpnomelane. Many outcrops close tothe LadnerGroup contactdisplay remnant vesicles, pillow structures,aquagene breccias, and weak layering,while their high sodium content(Table 6) indicates the presence of some spilitic lavas. Rare lenses of immature volcanic sandstoneand conglomerate are also seen,while bodies of gabbro-diorite are presentwithin the volcanic unit near Fmancipation mine. The age of thevolcanic rocks is uncertain and some rare examplesof interpillow cherts in thegreenstones have been examined for microfossils without

3 65 Figure 23. Fbglonal geology of the QroIIn-Pipestem-Emnclpation gold mines area.

66 success. However, at one locality east of serpentine Lske, a l-metre- widechert breccia horizon thatseparates pillowedgreenstones from the LadnerGroup contains conodonts of Qrly Triassic age (M. Orchard, personalcommunication). This horizon probably originated from pre- Ladnerweathering and concentration interpillowedof chert breccia material present in thegreenstones. This would stronglysuggest that thevolcanic rocks are Early Triassic in age.

Boththe Ladner and mzameen Groups are cut by a wide variety of intrusiverocks. A distinctivesuite of leucocraticquartz porphyry sills is restrictedto the HOzameen Group. These sills containlarge, rounded phenocrysts of quartzand some rare flakesof biotite, set in a fineto medium-grained quartz-feldsparmatrix. The quartzporphyries look fresh buttheir restriction to the Hozameen Group suggests th,nt theyp:redate thetectonic emplacement of this unit adjacent tb theserpentine belt.

TheLadner Group is cut bytwo main intrusivesuites. Cne forms(dykes, sills, and irregularmasses up to 300 metres inwidth that displalywide variations in textureand composition. Individual bodies are zoned with gabbroicand ultrabasic cores grading out to granitic cont.actzones. 'Ihe othersuite formsnarrow dykes and sills of feldsparporphyry that are locallysyenitic (Bateman,1911; Cairnes, 1924). Quartz veining with minorpyrite, arsenopyrite, and traces ofgold occur in some sills and dykes.Consequently Bateman (1911) and Cairnes(1924, 1929) considered theseintrusive rocks to be genetically related to some goldmineralization in thedistrict.

GOLD IIIEIERALIZATION IN THE BELT

GENER?+L

The locations of deposits andoccurrences comprising the Coquihalla gold beltare shown on Figure 22 and furtherdetails are listedin Tables 2 and 3. Most goldproduction has come from five deposits(Table 2): only the newlyopened Carolin MinesLtd. operation on theIdaho zone is currentlybeing worked. Information on earlygold production from the belt,particularly from the Aurum and Ward deposits, is poorlydocumented andunreliable. Nevertheless, until closure of theDnancipation nne in 1941,approximately 119 000 grams of gold had been won from the bel-t. Of this,the majority (90 104grams) came fromDnancipation mine, the most southerlydeposit in the belt (Fig. 22).

Carolin Mines Ltd. is planningto mill 1 350 tonnesofore per day, grading 4.2 grams gold per tonne (P. W. Richardson,personal communication). Shortly, one month'sproduction from theIdaho zone is expected to exceedthat from theprevious 70-year history of the belt.

IDAHO ZONE (CAROLIN MINE)

No futhersurface or underground mappingof theIdaho zone was undertaken by theauthorby during the 1982 fieldseason, althclugh labo.ratory

67 investigationof the ore geochemistry andpetrology continued. Hopefully undergroundmapping by J. T. Shearer and R.J.E. Niels of Carolin Mines Ltd.,together with a studyof the sulphidedistribution in the Idaho zone(Shearer, 1982), will delineatethe ore controlsand morphology of thedeposit. Underground work on theproperty (R.J.E. Niels, J. T. Shearer,personal communication) indicates that theIdaho zone consists of at least two majororebodies; a lower (No. 1 orebody), and anupper (No. 2 orebody),separated by highlysheared and faulted carbonaceous argillites. The upperorebody crops outjust north of the old Idaho adit (Ray,1982) and was discoveredduring the initial surfaceexploration. A rusty-weathering,13-metre-wide zone assaying up to 4 800 ppbgold out- croppingapproximately 160 metres south-southeastof the old Idaho adit, may bethe surface expression of the lower orebody.Comparative analyses on mineralizedand unmineralized wackes in the Idaho zone (Table 4) suggestthat mineralization was accompanied by theintroduction of silica, sodium andsulphur, the removal ofmagnesium, potassium, calcium and carbondioxide, and the conversion offerrous to ferriciron. Intro- ductionof sodium resultedin the formation of abundantwhite albite (?in3-5) inthe ore zone. Trace element analyses(Table 4) show thatthe theIdaho zone is weakly to stronglyanomalous incopper, arsenic, molybdenum, antimony,and tungsten.

Shearer(1982), in a study on the sulphidedistribution within the Idaho zone, made thefollowing observations:

(1) Mineralized samples fromthe zone are separableinto pyrite dominant andpyrrhotite dominant types. Consequently, the deposit may be zoned. (2) Small grains ofgold, up to 0.02 millimetre insize, occur either as inclusionswithin pyrite and arsenopyrite or as rims on pyrite and chalcopyrite. (3) Small grains of freegold, apparently spatially independent of sulphides, are presentinside some quartz, calcite, and feldspar crystals.

Theseobservations explain how samples 25163M and 25164M (Table4). which are arsenopyriterich and arsenopyrite poor respectively, could both containhigh gold values. They alsosuggest that economical gold mineralization is possibleinsulphide-poor parts of theIdaho zone. Thus,while arsenic is a pathfinderfor gold exploration in parts of the belt,gold could also occur without arsenic geochemical anomalies.

Examinationof thin andpolished sections from theIdaho zone reveals a complexhistory of mineralization,alteration, and structural deformation. The mineralizedwackes consist largely quartz,of albite- oligoclase, and calcite with lesser amounts of chlorite, sericite, and opaqueminerals. These opaques,which make upbetween 1 and15 per cent of therock by volume, are mainlypyrrhotite, arsenopyrite, pyrite, and magnetite. Less common opaques, decreasingin abundance, include chalcopyrite,bornite, andgold (Kayira, 1975). Ore specimens are

68 characterized by coarse,subhedral crystals of pyrite ,and arsenopyrite withfiner grained disseminations and clusters of pyrrhotite, magnetite, andpyrite. The magnetite showsno spatialassociation with SUI-phides and is theoldest opaque mineral present inthe ore. Arsenopyrite also appearsto have been introduced early because some crystalsare partly rimmed with small blebsof pyrite and pyrrhotite.

The Idahozone is characterized bya closelyspaced, irregular network of whitevein material, representingthe injection of many generations of quartz,calcite, and albite. lhe developmentof sigmoidal gash fractures andthe wide variationinvein deformation, from highlyfolded to apparently undeformed,suggests that the multistage in:jection occurred during a long periodof recurrent structuraldeformation. White quartz veins,generally less than15 centimetres wide, comprise the conmonest veinmaterial on megascopic scale. At leastthree generations are recognizedand all appearto postdate the main period of gold-sulphide mineralization. Many veinsare monomineralic but in others the quartz crystals are intergrownwith variable amounts of calci.te,albite, and clinozoisite; in rare instances there are small flakes of pyrobitumen. Some quartzveins that cut andpostdate the main F2 slatycleavage (see Table 1) are seenunder thin section to be foldedand contain strained quartzcrystals that are elongatedparallel to both the F2 foldaxial planesand the slaty cleavage. mese veins are interpretedto be ofsyn- F2 age,being injected after the main cleavagedevelopment, but before thdtperiod ofdeformation had ceased. Larger quartz crystals in these veins displayfinely sutured margins suggesting crystallization during strain(Spry, 1969).

Whilequartz veining is ubiquitousin the Idaho zone, calcite veining is far less abundantand tends to be localized. lhe calcite veins appear to postdateall other veining episodes and show no evidenceof folding. However,minor faultinghas occurred along some and in thinsection many calcitecrystals exhibit deformedtwin planes.

On themegascopic scale, albiteveining is less evidentthan either quartz or calcite. However, in thin section the effects of sodium metasomation are reflected by at least threegenerations of albitization. Disseminatedand partially altered albite-oligoclase (Pn3-15) crystals make up a significantproportion of the fine-grainedor'? groundma.ssand representthe oldest generation of albitic material. This disseminated albitic groundmass is cut by numerous thin,folded veins ofpoorly twinnedsecond generation albite. The youngest material generally forms veinlets anddisseminated masses throughoutthe ore zone. It consists of coarse,well-twinned albite crystals (An3-5)* up to El millimetres in lengthwith locally deformed twin planes.Locally,. small angular fragmentsofsulphide-rich ore areentirely engulfed inthis third generationalbitic material.

Pyritic argillites with abundant quartz veining occur withinand adjacent to theIdaho zone but these rocks generally contain no gold {R.J.E. Niels, personalcommunication) . Abundantminute carbonaceous lenricules *Identified by X-ray diffraction using a method described byBambauer, et dl., 1967. 69 areseen under thin section. They areelongated parallel tothe F2 chlorite-sericitecleavage (Table 1). These argillites haveprefer- entiallytaken up strain and arecut manyby faultplanes that are smeared with carbonaceousmaterial and marked by slickensiding. X-ray examination shows thatthe carbonaceous material in boththe fault planes andargillites is amorphous;thus the regional metamorphic grade was too low toproduce crystalline graphite.

In rareinstances, white quartzveins contain small flakes of pyrobitumen whose optical andphysical characteristics suggest it hasacquired a maturationequivalent to meta-anthracite (J. Kwong, personal communication). Thesepyrobitumen flakes are believed representto original amorphouscarbonaceous material derived from the wallrocksand meta- morphosedduring the quartz vein injection. Since meta-anthraciteforms between 238 and 266 degrees Celsius at an equivalentpressure ofabout 0.2 GPa (Brownlow, 1979), its presence may indicate the approximate temperaturepressure range attained in the Idaho zone.

MURPHY GOLD OCCURRENCE

The Murphy goldoccurrence is locatedapproximately 400 metresnorth- northwest of McMaSter pond (Fig. 23). It was discoveredin 1982 by prospector D. Murphy, whileinvestigating a soil geochemicalgold anomaly outlined by Carolin Mines Ltd. The mineralizationconsists of finegold withpyrite and arsenopyrite in a quartzvein between 5 and 20 centimetres in width. The veincan be traceddiscontinuously for 20 metres withinaltered greenstones immediately adjacent to their faulted contact withhighly sheared talcose serpentinites. This fracture zone represents thesteeply dipping Fast Hozameen fault;the quartz vein, however, dips verygently northeastward into the hillside. The darkbrick red soil overthe occurrence contains pannable gold.

The mineralizedwhite quartz vein contains small vugs linedwith clear quartzcrystals, and thesulphides are visuallyestimated to form less than 2 percent by volume.Gold is most commonly seenas a fine coating onchocolate brown alterationproducts; the lattercontains a mixtureof goethite,hematite, and lepidocrocite with some remnantpyrite. Else- where,fine gold is associatedwith both pyrite and arsenopyrite and, in rareinstances, it is free in thequartz. Both goldand sulphides occur atthe vein margins and veincentres.

SILT GEOCMISTRY

Approximately 80 silt sampleswere collected from streamswithin the mapped area;these have been assayed for gold, arsenic, chromium,copper, mercury,nickel, lead, antimony, zinc, andcobalt. No statistical analysis of the datahas been made yet,but the following points are noted:

70 TangentCreek, which drains the oldhancipation mine, is theonly stream with marked arsenic andmercury anomalies (152 ppn and 180 ppb respectively).

Some streams drainingthe serpentine belt are highlyanoma1.0~~ in chromiumand nickel(up to 0.11 per cent and 0.14 per cent :respectively).

Many streams drainingthe eastern side of Ladner#Creek Vall.ey are weakly to moderatelyanomalous inzinc (up to 287 ppn) . These streams drain the NeedlePeak pluton and its wide thermal meta- morphicaureole in the Iadner Group.

No anomalouscobalt or antimony values were recorded.

One large stream flowingsouthwestward from buntSnider into SowaquaCreek containsanomalous lead (58 ppn)and zinc (6015 ppn). This raises thepossibility that the stream drainagebasin is underlain by lead-zinc-silverveins, similar thoseto found around TreasureMountain 10 kilometresfurther west.

DISCUSSION

DEPOSITIONAL ENVIRONMENT AND STRATIGRAPHY OF THE LADNER [GROUP

Overall,the Ladner Group is an upward finingsuccession. It passes from a thin,heterogeneous, coarsely clastic unit at thebase into a much thickersequence of finely bedded siltstones and argillites. %e lowermost unitincludes discontinuous wedgesof coarse,poorly sorted material interbeddedwith lesser amountsof finersediment. This implies rapidly alternatingperiods of low andhigh energy deposition, the latter invol- vinghigh density turbidites and chaotic slumping. The ,extreme variation in thickness and character of the lower clastic unitsugqests that either rapidlateral facies changes existed or that the mari.ne transgression tookplace across an irregular basement topography.Overturned flame structures in some basalbeds indicate an easterlyderivation, while the assortedpebble lithologies show a sourceunderlain by greenstones, granitic andgabbroic rocks, flow-banded acid to intermediate volcanic rocks,and some limestones.

The finely bedded siltstones and argillitescomprising the higherportion of theLadner Group succession(Ray, 1982) are believedto represent DE turbidites (Eouma, 1962) depositedin a low energy,deeper water environment. In parts, thissequence contains thin, impersistent horizons of coarse wackewhich reflectthe periodic influx ofhigher energy turbidite sediments. Cne such wacke horizon is traceable for 900 metres andhosts thegold mineralization at Pipestem mine. It alsocontains be1.emnites andbivalves, the only Ladner Group fossilsseen in the district.

71 GREENSTONES

The greenstonesare generally massive but adjacent to the Iadner Group contactthere are aquagene breccias and vesicularpillowed basalts, while further west, adjacentto the Qst Hozameen fault,the unit includes bodiesof gabbro-diorite (Fig. 24A). These bodies may haveformed feeders tothe overlying lavas andthus the present westerly progression from submarineextrusive basalts to plutonic gabbros could reflect a gradation from nearsurface to deeperlevels.

The IadnerGroup-greenstone contact is believedto represent an unconformity.This is tentativelysupported by microfossilevidence and by thepresence of bothgreenstone and gabbroicclasts in thebasal Ladner Groupconglomerates. These suggest that the Lower Triassicvolcanic pile wasdeeply eroded prior to the onset of Lawer Jurassic(Coates, 1974) LadnerGroup sedimentation.

EVOLUTION OF THE COQUIHALLA SERPENTINE BELT

Extensiveserpentine belts throughout the world are believed to represent eitheroceanic crust or upper mantle material that was emplaced either as low temperature,plastic intrusions along vertical fractures or as slices in allochthonousthrusts formedduring major orogenic plate movements. Serpentinebelts are generally associated with fundamental fractures that arebelieved to mark major crustalboundaries (Shackleton, 1976). The Coquihallaserpentine belt separates two importantgeological units, the Hozameen andIadner Groups, that are of differentage and contrasting character. It is bounded by major fracturesthat are interpretedto be refoldedthrust faults. Field and laboratorydata explaining the origin anddevelopnent of the Bquihalla serpentine belt is preliminaryand inconclusive;consequently two alternative models arepresented (Figs. 24B and 24C). 'Fne serpentinebelt may representobducted oceanic crust (Ray, 1982;Fig. 24B) which originallyunderlay, andformed a basement to,the Hozameen Group. In this model bothallochthonous units were emplaced by easterlydirected overthrustingthat caused tectonic inversion in some parts of theIadner Group (Fig.24B). mis model suggests thatthe main overthrustingoccurred along the East Hozameen fault, and thatthe serpentinites andgreenstones areunrelated. However, this obduction model is difficultto reconcile with the platetectonic models proposed by Wnger, et dl. (1972) and Monger (1 977) to explain the formation of the CanadianCordillera. Furthermore, X-rayand thinsection examination of rocksimmediately adjacent tothe Bst HOzameen fault reveals no hightemperature minerals like thosefound in thethin, basal aureolesunderlying many obducted,Alpine-type ophiolite complexes (Williams andSmyth, 1973) .

An alternativeproposal (Fig. 2412) is thatthe serpentinites and greenstonesare related, and representlower and upperoceanic crustal material which originallyunderlay and actedas basement to the Ladner Group. Structuralinversion of theseunits tookplace during easterly

72 WEST EAST WHF EHF

LEGEND

HOZAMEEN GROUP [7 LADNER GROUP P= PILLOWED VOLCAN1C:S WHF = WEST HOZAMEEN FAULT SERPENTINE [3 GABBRO EHF = EASTHOZAMEEN FAULT VoLcANlc GREENSTONES + YOUNGING DIRECTION INTHE LADNER GROUP

A = PRESENT DAYDIAGRAMMATIC EASTNVEST SECTION ACROSS THESERPEhTlNE BELT IN THE EMANCIPATIONMINE VICINITY B AN0 C = TWO ALTERNATIVEMODELS SHOWINGPOSSIBLE EVOLUTION OF THECOOUIHALLA SERPENTINE BELT B = EASTWARDOVERTHRUSTING OF THEHOZAMEEN GROUP AND UNDERLY1h:GOCEANIC CRUST ALONG THE EAST HOZAMEEN FAULT, CAUSING TECTONIC INVERSION IN THE VOLCANICS AND LADNER GROUP C = EASTWARDOVERTHRUSTING OF THEHOZAMEEN GROUP ALONG THE WEST HO2AMEEN FAULT CAUSINGTECTONIC INVERSION OF THELADNER GROUP ANDUNDERLYING OCEANIC CFIUST

Figure 24. Evolution of the Ccqulhal la serpentine belt.

73 overriding of the Hozameen Group butthe main movement in this modeltook place alongthe West Hozameen fault. me LadnerGroup, thegreenstones, andthe serpentinite-gabbro belt could represent respectively the clas- sical oceaniclayers 1, 2, and 3 (Cann,1974) although no sheeteddykes are recognizedin the Coquihalla belt.

Differenttectonic relationships are impliedin these two models,but in both,the ladner Group is interpreted to bedeposited on oceaniccrust, andthe HOZameen Group is viewed as allochthonous. However, interpretation is complicated by accompanying right lateral transcurrent movements alongthe Hozameen faultsystem, similar to thatdescribed in othermajor strike-slipfaults in the Canadian Cordillera (for example, lkmpleman- Kluit, 1977;Monger, 1977) and by subsequentdeformation and refolding.

GOLC MINERALIZATION

An overallexamination of deposits andoccurrences inthe Coquihalla gold belt(Fig. 22; Tables 2 and 3) revealsthe following features:

Coquihallagold belt mineralization is proximal to greenstones, fault-boundedserpentinites, and small outcrops of fuchsite-bearing quartzcarbonate rock. mese associations are similar tothat seen at theBralorne-Pioneer mines (Cairnes, 1937; Joubin, 1948), the Cassiar gold camp (Panteleyevand Diakow, 1982).and the Mother Lode belt of California (as noted by Cairnes, 1929).

lhe occurrencesand deposits, with the possible exception of the Norm andGeorgia 2 occurrences whose precise locations are uncertain, are situated east ofthe East Hozameen fault(Fig. 22).

?he gold is generallyfine grained; coarse visible gold is relatively uncommon throughoutthe belt (a notedexception is the Aurum mineralization).

All goldmineralization in the belt is in highlyfractured host rocks. It was accompanied by the introductionof silica which formseither discreet, generally narrow quartz veins (Emancipation mine, Murphy occurrence,bnument vein) or widerzones of intense networkveining and diffuse silicification (Idaho and kMaster zones).

Gold throughoutthe belt is associatedwith varying degrees of sulphidemineralization (see Ray, 1981).These sulphides include pyrite,arsenopyrite, pyrrhotite, and chalcopyrite.

Gold mineralizationoccurs in a widevariety of fractured host rock typesthat includes greenstone (Emancipation mineand Murphy occurrence), felsite porphyry sills (Ward and migrant), andmetasedi- mentaryrocks theofIadner Group (Idahoand WMaster zones, Pipestem, Rushof theBull, Gem, GoldenCache, Home X, and the Spuz

74 occurrences). However, thesehost rocks share a common characteristic -- theyare more competent than thesurrounding country rock. Consequentlythey were brittle and subjectto openspace fracturing. Gold mineralizationin the belt is thereforepreferentially hosted eitherwithin the wackesand felsite sills or in faultzones between competentand incompetent units, likethose separating greenstones frommetasedimentary rocks.

Studiesare incomplete, but few occurrences in thebelt, including theIdaho zone, show enrichment in mercury. However, TangentCreek, whichdrains the hancipation mine,hasanomalous mercury silt values(up to 180 ppb mercury)which suggests a gold-mercury association in thisdeposit.

Gold mineralization in the Spuz occurrenceand at theIdaho :zone is associated with weak tungstengeochemical anomalies.

The source of theIdaho zone gold mineralization is uncertain. How- ever, the introduction ofsodium, which is probablyderived f.rom the nearbyspilitic volcanic rocks, suggests that the qreenstones could representthe source of thegold.

Weathered,gold-bearing outcrops of the Idahoand Wklaster zoc.es are characterized by black manganese oxideand rusty staining, together with sulphidemineralization and a densenetwork of quartz veins. However, many othersimilarly mineralized quartz veined outcrops exist throughout thebelt, particularly north of the Aurum deposit(Fiq. 23) where the lower clastic unit of theLadner Group is bestdeveloped. A few carry gold but most appear barren and there is no reliablefield method for distinguishingthese two, althoughoutcrops with chalcopyrite t:end to carry goldalso. Future studies may revealzoning patterns, raising a possibilitythat someof thesebarren sulphide-bearinq, quartz veined outcropscould pass into gold-bearing ore at depth.

The temperature of mineralization in theIdaho zone is uncertain., How- ever, the stabilitydata for meta-anthracite from theIdaho zone quartz veins suggest temperatures of 250 degrees Celsius were attained. This lieswithin the temperature range established by fluidj.nclusion studies for many vein-typedeposits (Spooner, 1981 ) .

ACXWCMLEWIEWTS

The authorwishes to thank the managementand staff ofCarolin MinesLtd. andAquarius Resources Ltd. for their activecooperation andencourage- mentduring this project,particularly D. G. Cardinal, K. ODllins, C. Hrkac, R.J.E. Niels, P. W. Richardson, and J. T. Shearer. Thanks are alsoexpressed to M. Orchardof the GeologicalSurvey clf Canada forthe preparation and identification of microfossilmaterial and tothe staff ofthe B.C. Ministry of Energy, Mines andPetroleum Resources Laboratory foranalytical andX-ray work. W. J. WMillanand T. H5y edi-tedthe manuscript. The fieldwork was helped by thecontinued excellent perform ance of PatrickDesjardins as field assistant.

75 TABLE 1. STRUCTURALHISTORY OF THE CAROLINMINE AREA

Late faulting.

Sporadically developed, minorconjugate folds associated with kink banding and crenulation c i eavage.

Major asymmetric folding of the Ladner Group. Folds have subhorizontal axes with southeast- striking axial planes that dip steeply northeast. No associatedmetamorphic axia I planar fabric recognized.

F2 Major disharmonic folds having subvertical. southeast-striking axial planes and gently plunging axes. It is associatedwith the regional axial planar slaty cleavage and mineral I Ineationin the Ladner Group. Major disruption and quartz veining along some fold limbs and axial planes.

Widespread structural inversim of the Ladner Goup and greenstones, related to the easterly overthrusting of the allochthonaus Hozameen G-oup. No associatedaxla\ planar tabric recognized.

Early to MiddleJurassic ? Depositionof the bdner Goup sedimentary (bates, 1974) rocks. - Unconformlty -

EarlyTriassic 7 Submarine volcanism with extrusion of pillowed basalis(greenstones).

TAME 2. MAJORGOLD PRODUCERS IN THECOQUIHALLA GOLD BELT (seeFig. 22)

No. on Name of Yearb) of Tot a I Sources Fis 22 Mi ne Pro&ction Production (9) Au As

I Emancipation 1916-1941 90 104 18 818 1

2 Aurum 1930-1932 16 578 3 017 1 1939-1 942

3 Idaho1981-1982 zone 216 253 Nat 2 (Carolin mine) reported

4 Pipestem 1935-1937 8 460 1 151 1

5 nard 1905 4 199 Nat 1 reported Sources 1 B.C. MineralInventory Fi la 2 Goldshipped up to bcember 31, 1982; P. W. Richardson,personal comnu n I cat ion.

76 TABLE 3. REPORTEDGOLD OCCURRENCES IN THECOQUIHALLA GOLD BELT (see Flg. 22)

No. on Name btal Is Sources Fig. 22

6 Broken HI I I Slngle quartz vein up to 3 metres wide and 60 1 metres long in LadnerGroup slates closo to thelrcontact with greenstones. hcertaln gold values with pyrlte, arsenopyrite and rare galena.

7 Snarstorm Twelvemetrelongadit along minerailzed zone 1, 2 (Plttsturg) between Ladner Group and volcanic greenstones. plartz veln up to 3 metres wlde wlth pyrite, arsenopyrite,pyrrhotite. and gold Calrnes (1924) reports gold values of up to $8.(10 per ton.

8 Montana GoldandDvrltkbearina .. 5tentimstrewI - de 11 quartz velns In greenstones close to contact with Ladner &cup.

9 Rushof the Bull Two narrw(IOsentlmetre) quartz velns. 2 mineralized with coarse arsenopyrlte ami free gold.Velns cut Ladner G-oup slatesnew their contact with a feldspar porphyry !;I (I.

10 GoldenCache At least six narrarquartz velns sparin'gly 2 mlneralized wlth pyrltearsenopyrite an1low goldvalues. Velns belleved to Ile clo!;e to the Ladner Group-volcanic greenstone colitact.

11 Master zone Networkquartzvelnlngpyrite, wlth 15 arsenopyrite,and gold, hosted in hlghl!r fractured, Ladner0-oup wackes and SIIt!;tones close to their contact with greenstones. Mlneralizatlon and netwrk veinlng closttly resembles that in the Idaho zona

12 Murphy Visiblegold with pyrite and arsenopyrlte 15 hosted In a thin. vugglquartz vein cuttlng greenstone Close to thelr faultedcontaczt with serpentlnlta

13 Gem Two-metrewide quartz vein wlthln Ladner 2 G-OUD. Bothveln and wal Irock shu soarse pyrtie-ersenopyrite mlneraliiation wijh pannable gold,

14 Star @art2strlngers up to 15 centimetreswlde 12 cutting Ladner Group rocks, carry pyrite, arsenopyrlte,and low goldvalues.

15 Home x Numerous thlnquartz stringers containlng 3, 15 pyrlte,arsenopyrlte, and Iw gold values. Velns cut black slates of the Ladner Q-wp close to their contact wlth a fosslliffrous wacke horizon. A collapsed adit of unknown length is on property.

77 TABLE 3. REPORTEDGOLD OCCURRENCES IN THECOQUIHALLA GOLD BELT (Continued)

No. on Name is btai Sources Fig.22

16 Georgia 2 Preciselocationuncertain. Fyrite, 4, 15 arsenopyrite, and gold within faulted diorites (probablypart of greenstonepackage). Some contusionover gold values. Cairnes (1929) reports 2.5 tons of ore gave $9.00 per ton g0lQ

16 Norm vicinitythe Claim in are ot Georgia 2 5, 15 ocarrence near Sp Ider Peak. Go I d geochemi ca I anomalies and pannable gold fromquartz- veined, mripositefuchsitebearing rocks.

17 Emi grantMinor quartzgold in veins associated with 6 feisic porphyry silis intruding the Ladner Croup slates.

18 Roddick No geologicaldescriptim availabia in 1901 7 adits and crosscuts 106 metres in length were driven through material valued at $15.00 to 1625.00 per ton gold,

19 Marvel 19 No geologicaldescription avaiiabia in 7 1906 existing adits were extended and a slrstanp mi I I instal led.

20 Spuz A, 8, G, and Weak goldmineralization in quartz veins and 10, 9. Monmnt siiicified zones withinthe LadnerGroup 15 close to the Hozameen fault. hemajor vein, the Monment, is up to 2 metres wide and traceablefor 80 meters. It carriespyrite, withrare arsenopyrite, chalcopyrite, and gold.Gold also found associated with rare scheelite in felslc porphyry sills.

21 Majestic 21 No geologicaldescription available. 11

22 Gold22 bin No geoiogicaldescription available. 13

23 Gold CordGold 23 No geologicaldescription available. 14

hurces 1 Cairnes, 1920. 2 Qirnes, 1924. 3 Minister ot Mines, B.C., AnnualReport, 1933 4 Cairnes, 1929. 5 B.C. Ministry of Enerq,Mines & Pet. Res.. Exploration in B.C., 1978 6 Bateman, 1911. 7 B.C. Mineralinventory Fi le, MI 92H/NW-l7. 8 Minister of Mlnes, B.C., hnuai Report, 1906. 9 Cochraneand Littlejohn. 1978. IO Cardinal, 1982. 11 B.C. Mineralinventory File, MI 9a;l/NW-33 12 B.C. Mineralinventory File, Mi 92H/NW-14. 13 B.C. Mineralinventory Fi le, Mi 92H/NW-32 14 0.C. MlneralInventory File, Mi 92i/MW-31. 15 Observed by author.

78 TABLE 4. HOLE ROW ANDTRACE ELEMEM ANALYSES. A CWA2ISON BETWEEN MINERALIZED AND UNMl NERALIZEOWAWES FRCM THE IDAHO ZONE (CAROLIN MINE)

25163M ' 25164M' 25167M' 25168M225167M'25164M'25163M'

60.62 53.11 48.92 15.42 14.51 14.05 0.45 1.20 0.22 3.89 7.94 6.26 0.68 1. I6 3.30 2.37 4.49 9.07 9.09 7.81 2.45 0.09 0.30 2.84 1.00 1.22 0.83 0.07 0.1 1 0.13 2.78 3.46 6.85 1.91 3.4 I 0.1 2

16.0 3.5

'Suiphlderlch wackes In Idahozone sharing aIbltemetasomtlsm and abmdant quartz veining. 2UnmlneraIized wackes adjacent to the Idaho zone. krm cluartz veining but no sulphldes or albitic alteration.

79 TABLE 5. WHOLE ROO( AN0 TRACE ELEMENT ANALYSES OF VARIOUS SEFPENTINITE SAWLES FRCM THECOQUIHALLA SERPENTINE BELT AN0 ELSEWHERE

25478l 25419 2548Z3 254864 A B

39.41 36.30 41.15 35.40 40.7 4 1. 7 1.15 5.99 0.32 0.59 1.0 0.8 38.29 36.20 39.4 1 31.26 36.4 38.5 0. 14 0.05 <0.01 0.18 0.1 0.4

<3 <3 <3 8 3 7 6 I1 7 30 5 20 <3 7 <3 <3 59 55 58 14 0. 15 0.24 0.18 0.1 0 8 100 8 16 <3 <3 <3 3 0.24 0.14 0.27 0.24 12 12 IO 12 QO QO QO QO

~n per cent except as noted

lAntigoritebastlterIch serpentlnlteuith sore rermant enstatlta Ccqulhal la serpentine belt. 2AntigoriterIchserpentinlta Coqulhalla serpentine belt. 3AntIgor1ter1chserpentlnlta Coqulhal la Serpentine belt. %erpentine with antlgorlte pseudomorphs atter ollvlna Coquihalla serpentlne belt.

A Sarpentlnltederlved fromdunlta Cornwall, England (Plrsson and Knopf, 1966). B Serpentlnltederived trornpyroxenlte. hunt Olablo, Calltornla (Plrsson andKnopt, 1966).

80 TABLE WHOLE6. ROO( AN0 TRACEELEMENT ANALYSES OF VARIOUS VOLCANICGREENSTONE SAWLES

2 5466' 254703 2547:fl

50.16 48.58 46.26 13.77 14.81 13.2.r 3.16 7.33 6.60 7.86 6.86 7.41) 7.20 4.58 3.51 0.02 0.06 0.6'3 1.27 1.78 1.81 0.19 0.19 0.1'1 1.17 3.34 4. I ,1 0.10 0.20 0.2'5 6.90 0.01 4. 9'3

0.03 0.0 I 0.02 0.005 0.006 0.037 40 90 70 22 38 30 20 25 23 14 21 59 37 53 30 32 <3 <3 26 31 39 17 12 12 33 QO QO

In per cent except as noted

'Augltebearing plI lared greenstona East of Serpentine lake. 2Sulphldkbearinq carbonate veined greenstone. Emanclpation mine. 3Aug1tebearlng altered volcanlc greenstone sharing aquagene brecciationCarolln mlne. 4Alteredgreenstone volcanlq I3-I 11 core Sanple. South of PI pestem mi ne.

81 TABLE 7. WHOLE ROO( ANDTRACE ELEMENTANALYS IS OF MBBRO IC ROCKS WITHIN THE COOUIHALLA SERPENTINE BELT

25481' 254832 50.19 48.73 13.15 14.44 7.16 6.92 9.66 11.09 4.09 3.60 0.05 0.12 1.66 1.37 0.19 0.18 122 0.16 0. 18 0.12 0. IO 0. I4 0.08 0.08 0.15 0.03 9.03 8.25 1.31 1.21

0.05 0.06 21 33 80 66 24 24 26 26 70 57 30 71 <3 <3 53 56 8 10 QO QO

In per cent except as noted

'Altered augltehornblende gabbro. 15 mi le C-eek Bldge. 'Altered gabbro. East of Serpentine Lake.

82 REFERENCES Anderson, P. (1976): Oceanic Crust andArc-Trench Gilp Tectonj.cs in SouthwesternBritish Columbia, Geology, Vol. 4, pp. 443-446. Bambauer, H. [I., Corlett, M., Eberhard, E., andViswanathan, K. (1967) : Diagrams forthe Determination of Plagioclases Using X-ray Powder Methods, Schweiz. Min. Pet. Mitt., Vol.47, pp. 333-349. Bateman, A. M. (1911): Geology of maser Canyon and Vicinity,Etitish Columbia -- SiwashCreek Area, Geol. Surv.,Canada, Summ. Rept., 191 1, pp.125-129. Bouma, A. H. (1962) : Sedimentology of some FlyschDeposits, Elsevier Pub. Co., Amsterdam, 168pp. Brownlow, A. H. (1979):Geochemistry, hglewood Cliffs, New Jersey, Prentice-Hall Inc., 498 pp. Cairnes, C. E. (1920):Coquihalla Area, British Columbia, Geol. Surv., Canada, Summ. Rept.,1920, Pt. A, pp. 23-42...... (1924):Coquihalla Area, British Columbia, Geol. Surv., Canada, Mem. 139,187 pp...... (1929) : The Serpentine Belt Coquihaltaof Region, Yale District, British Columbia, Geol. Surv., Canada, Summ. Rept., 1929, Pt. A, pp. 144-197...... (1937): Geologyand Mineral Deposits of BridgeRiver Mining Camp, British Columbia, Geol. Surv., Canada, Mem. 213,140 pp,, Cann, J. R. (1974): A bdel for CceanicCrustal Stru,:ture Developed, Geophysics Jour. Roy. Astron. Soc., Vol.39, pp. 169-187. Cardinal, D. G. (1 981) : Hope Group Property(Fimancipation Mine), dquarius Resources Ltd., unpub. rept...... (1982) : Report on Portions of the Spuzzum Group Properties, Aquarius Resources Ltd., unpub. rept. Coates, J. A. (1974) : Geologyofthe Panning Park Area, Geol. Surv., Canada, Bull. 238,177 pp. Cochrane, D. R., Griffiths, D., and bntqomery, J. T. (1974): Aurum- Idaho-Pipestem Project, B.C. Ministry of Energy, M~nes& Pet. Res., AssessmentRept. 4852. Cochrane, D. R. andLittlejohn, A. L. (1978): Spuz A, B, and G Claims, Longbar Minerals Ltd., B.C. Ministry of Energy, M~nes& Pet. Res., AssessmentRept. 6962. Daly, R. A. (1912): Geology on theNorth American Cordillera at the Forty-NinthParallel, Geol. Surv., Canada, Mem. 38. Joubin, F. R. (1948): %alorne andPioneer Mines, in St.ructura1 Geology of Canadian Ore Deposits, C.I.M., Jubilee Vol.,pp. 168-177. Kayira, G. K. (1975) : A Mineralographicand Petrograpllic Study of the GoldDeposit of the Upper Idaho Zone, Hope, British Columbia,unpub. B.Sc. thesis, University of British Columbia. McTaggart, K. C. and Thompson, R. M. (1967) : Geology of Part of the NorthernCascades in southernBritish Columbia, Cdn. ,70ur., Earth Sci., vol. 4, pp.1199-1228.

83 Monger, J.W.H. (1970): HopeMap-Area, West Half (92~w1/2), British Columbia, Geol. Surv., Canada, Paper69-47, 75pp...... (1 975) : Correlation of mgeosynclinal Tectono-Stratigraphic Belts inthe North American Cordillera, Geoscience Canada, Vol. 2, pp. 4-10...... (1977): Upper Paleozoic Rocks of the Western CanadianCordil- lera and Their Bearing on CordilleranEvolution, Cdn. Jour. mrth Sci., Vol. 14, pp. 1832-1859. Monger, J.W.H., Souther, J. G., andGabrielse, H. (1972) : Evolutionof theCanadian Cordillera: A PlateTectonic Model, Am. Jour. Si., Vol. 272, pp.577-602. Panteleyev, A. and Diakow, L. J. (1982):Cassiar Gold Deposits, McDame Map-Area, B.C. Ministry of Energy,Mines & Pet. Res., Geological Fieldwork,1981, Paper 1982-1, pp. 156-161. Pirsson, L. V. andKnopf, A. (1966) : Rocksand Rock Minerals,John Wiley, p. 331. Ray, G. E. (1981) : Geologyand Gold Mineralization of theCoquihalla Belt, withParticular Reference thetoCarolin Gold Deposit, in Rocksand Ores of theMiddle Wes, Geol. ASSOC. Can., Cordilleran Section,February, 1981, Abstr., pp. 24, 25...... (1982) : Carolin Mine -- Coquihalla Gold Belt, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp. 87-101. Shackleton, R. M. (1976):Shallow and Deep Level Exposures of Archean CrustinIndia and Africa, in The mrlyHistory of the Farth, B. F. Windley (editor),Wiley, pp. 317-321. Shearer, J. T. (1982) : PreliminaryInvestigation on SulphideDistribu- tion,Idaho Orebody, CarolinMines Ltd., unpub. Progress Fept. NO. 1. Spooner, E.T.C. (1981) : FluidInclusion Studies ofHydrothermal Ore Deposits Fluidin Inclusions: Application to Petrology, L. s. Hollisterand M. L. Crawford,editors, Min. Assoc. Canada, Short Course,Calgary, May, 1981, pp.209-240. Spry, A. (1969):btamorphic Textures, Pergamon Press, London. Templeman-Kluit, D. J. (1977) : Stratigraphicand Structual Felations betweenthe SelwynBasin, Pelly-CassiaPlatform, and Yukon Crystalline Terrane, Geol. Surv., Canada, Paper 77-1A. Williams, H. andSmyth, W. R. (1973):Metamorphic Aureoles beneath OphioliteSuites and Alpine Peridotites: 'Ectonic Implications with West NewfoundlandExamples, dm. Jour. Sci., Vol. 273, pp. 594-621. Wright, R. L., Nagel, J., andMcTaggart, K. C. (1982) : Alpine Ultramafic Rocksof Southwestern British Columbia, Cdn. Jour. Earth Sci., vol. 19, pp. 1156-1173.

84 THE BLUESKY - A STRATIGRAPHIC UARKW IN NORTHEASTERN BRITISH COLUMBIA (931, 0, P)

By G. V. White

Over thepast 25 yearsthere has been extensive drilling by both petroleumand coal exploration companies southof the John Hart Hi.ghway in northeasternBritish Columbia. Correlation offormation tops from the geophysical logs takenfrom the drillholes allows accurate predicti-on of formationthicknesses over an extensive area. As part of a study of Lower Cretaceoussedimentary rocks in northeastern Briti:sh Columbia, an isopach map of theBluesky transitional unit (Fig. 25) was producedfrom drill hole information.

TheGething Formation as described by D. C. FClgh (1960) consists of 'grey,silty, fine- to coarse-grained siltstones, grey to brownish grey, silty,fine tocoarse-grained sandstones, and dark grey andblack, carbonaceousshales and coal.' Wst of thebetter coals are found :,n the UpperGething and these coals are soughtafter by numerous exploration companies innortheastern British Columbia. It is because rmch of the coal is found in theupper section that it is important t.o establishthe topofthe Gething Formation, which is marked by a transitional unit calledthe Bluesky.

The Bluesky is a transitionalunit betweencontinental sedimentary rocks ofthe Gething Formation and marine shales ofthe overlying Moosebar Formation. 'he Bluesky was firstdescribed in 1954 by the Alberta Study Group who took theirdescription from theBluesky well No. 1 in Alberta (4-29-81-1, W6J. The Bluesky atthis location was found inthe in-terval 834 metres and856.5 metres, with a totalthickness of 2;!.5 metres.. The unit was described as 'fine- to medium-grainedsandstone with intnrbeds ofshale. ' %e top was characterized by black,rounded chert granules and pebbleswhich decreased in abundance downward. Glauconite was common in this type section of the Bluesky.

In 1960, D. C. Algh proposedusing Fort St. John well No. 10 from Tinter- val 987.6 metres to 999 metres as thetypical representative B:Luesky sectionin northestern British Columbia. It was described as '24 feet [ 7.3 metres] of veryfine-grained, glauconitic sandstone with carbon- aceousinclusions, 5 feet [1.5 metres] of glauconitic,sandy shale and 11 feet f3.4 metres] ofporous, fine-grained, glauconitic sandstone." EUyh extendedhis study of the Bluesky in British Columbia tothe area north ofthe John Hart Highway, where petroleumexploration corrpanies had extensivelydrilled.

In thispreliminary study emphasis is beingplaced on theBluesky unit because it marksthetop theof Gethiny Formation, which coiltains importanteconomic reserves of coal. As well, in sonenortheastern British Columbia localities,the Blueskycontains siqnificant oil a.nd gas

85 Figure 25. Isopach map of theBluesky unit, Gathing Formtlm south of PeaceRiver In northeastern British Columbia.

86 reserves. Furtherexamination of outcrops,drill core, and geophysical logsduring this study will emphasizethe distribution and charact:er of theBluesky unit throughout the Peace River Coalfield.

REFEFlENCES

AlbertaStudy Group(1954) : Lower Cretaceous of thePeace River Region, Western Canada SedimentaryBasin, in Western Canada Sedimentary Basin, Am. Assoc. Pet. Geol., R. L. Rutherford Memorial Vol., pp. 268-278.

Hudson, J. A. (1979): K3p - Structure on Top of Bluesky -' Gething, B.C. Ministry of Energy,Mines & Pet. Res. Karst, R. H. (1981):Correlation of the lower CretaceousStratigraphy of NortheasternBritish Columbiafrom FoothillsPlains,to B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1980, Paper 1981-1,pp. 78-89. Pugh, D. C. (1960) : The SubsurfaceGethinq and BlueskyFormations of NortheasternBritish Columbia, Geol. Surv., Canadd, Paper 60-1, 20 PP.

87 MONTE LAKE

LEGEND Y

RECENT

LANDSLIDE DEPOSIT

EOCENE

PINK BEDS. PORPHYRITIC iPYROYENEl VOLCANICS

=GREY BEDS. FINE-GRAINED FELSIC VOLCANICS

=BROWN BEDS. MOSTLY BASALTIC LAVASAND BRECCIA

PRL-TERTIARY

BASEMENT CRYSTALLINE ROCKS. ARGlLLITES. AND

Flyre 26. Sketch map of the geoloq of the Salmon River area,

88 BASALTS OF THE I(A13LooPS GROUP IN SALMON RIVW ARE& (82L/5)

By B. U. Church and S. G. Evans

TheSalmon RiverValley is the site of severallarge landslides 1:Evans andCruden, 1981) which are of some concernfor road and power accessto the Douglaslake area tothe west andregions beyond.Source cmf the slidesappears to bemainly incompetent Tertiary basaltic units exposed onmuglas Iake Road 8.5 to 10.5kilometres and 12.5 to 15 kilometres south from Westwold (see Fig.26). This report considers the strati- stratigraphicsetting and petrologyof the basalts.

The totalsection of lkrtiary rocks in the region exceeds 750 metres, comprisingalternating lava flows andbreccia. Reddish weathering augiteporphyry, exposed on the upper faces of slideescarpments and in cliffs, is theuppermost unit inthe local volcanic assemblage. This formation is approximately 450 metres thicknorth and west of the?ahon Riverand wedges out to the south where the unit lapsonto pre-Tertiary formations. A greyaphanitic sequence of lavas andbre,:cias below the augiteporphyry thickens northerly toward Monte Hills, attaining maximum thickness of about 200 metres. The basalunit in the section is an assemblageof basaltic rocks 200 to 250 metres thick. It rests on pre- Tertiaryargillites near the 17-kilometre marker on the muglaslake Road. The basalts are crumbly,dark brown, oftenhighly vesicular, and occasionallyrich in zeolites which fillcracks andamyg,iales. Tuffac- eous bandswith clay partings in the basaltic unit are glidesurfaces for some of thelandslide movement.

Correlation of the Salmon Rivervolcanic rocks with other Tertiary sections is uncertain owing tothe limited nature ofdetailed mapp:tng in the area. lhe 'basaltassemblage' of this report is essec.tiallythe same as the'basal beds and brown beds'of mans andCruden (1981). These appearto correlate withthe Monte IakeFormation ofIming (19el. p. 1472)and the Attenborough Creek Formation of Church(1980, 1982) ,, me ageof two samples ofSalmon Riverbasalt (Table 1) was determined by J. Harakal(University of British Columbia), by K/Ar analysis ofwhole rockspecimens, as 48.6 and 49.4 Ma. lhese values are comparable to the results of 4822 Ma reported by Mathews (1964) forthe Att.enboroughCreek ash.

TABLE 1. WHOLE ROCK K/AR ANALYSIS OF TWOSALMON RIVER BASAL1 SAM'LES

Field Latitude LongitudeLatitude Field K Ar*40 Ar*40 Age No. North west z (cc/grn) z (Ma )

EV-3 i19°54.3'50'26.6' 4.497 2.31 49.4t1.7 93.8 EV-5 500224' 119*52.2' 1.88 3.591 95.2 48.6r1.7

89 N w ?i 4 c

90 The augite porphyry and grey aphanitic sequencesover1yir.g the basaltic formation correspond to the ‘redbeds andsalmon beds‘ of Evansand Cruden(1981). %ey may correlate in part withthe mktalramin Formation ofminq (1981) near Write Lake butthere is no clear tie with the Tertiary section in the Terrace Mountain area.

Petrographicstudy of the basalts shows a predominanceofsmall (less than0.25-millimetre) laths of plagioclasealong with an ,ample admixture of olivine,of pyroxene, and magnetite grains;accessory biotite and apatite;scattered olivine and, less commonly, pyroxenephenocrysts. Amygdalesand cracks are commonly filledwith calcite, brown chlorite, andzeolites such as heulandite,chabazite, thomsonite, stilbite, and less frequently,stevensite, levyne, and offretite.

Exceptfor the most felsic rock in the collection (No. 4),chemical analyses of volcanic rocksfrom the Salmon River area show re1ativel.y low alumina content,averaging 13.5 per cent(Table 2). S,ample No. 4 is similar toan andesite (No. lo), from the Monte Lake area. Sample! Nos. 1, 5, 7, and 11 are typicalolivine basalts; No. 12 is pyroxenerich. Thesebasalts tend to weather and disintegrate readily, especially the breccias andhighly vesicular phases.

Basal basalticrocks of the KamloopsGroup in the Salmon Riversection bear greatestlithostatic pressure. Consequently, landslides occur along tuffaceousbands and other incompetent zones, particularly where the volcanicrocks are altered, highly vesicular, or fragmental. Weak zones are commonly intenselyfractured and consist of redoxidized rocks with clay on slip surfaces andabundant calcite or zeolite in cracks and joint sets.

REPERENCIS

Church, B. N. (1980) : Geology ofthe Wrrace Mountain ‘mrtiary Outlier, B.C. Ministry of Energy, Mines & Pet. Res., Prelim. Map 37...... (1982) : Notes on the Penticton Group: Progress Repor-t on a New StratigraphicSubdivision of the Tertiary,South-Central British Columbia, B.C. Ministry of Energy, Mines & Pet. >?es.,Geological Fieldwork,1981, Paper 1982-1,pp. 12-15. Evans, S. G. andCruden, D. M. (1981):Landslides in the Kamloops Group inSouth-Central British Columbia: A ProgressReport, in Current CurrentResearch, Pt. B, Geol. Surv., Canada,Paper 131-1B. Ewing, T. E. (1981):Regional Stratigraphy and Structural Settingof the KamloopsGroup, South-CentralBritish Blumbia, Can. Jour. Earth Sci., Vol. 18, No. 9,pp. 1464-1477. Mathews, W. H. (1964):Potassium-Argon Aqe DeterminationsofCenozoic Volcanic Rocksfrom British Columbia, Geol. SOC. of ,Am., Bull., vol. Vol. 75, No. 5, pp. 465-468.

91 B 9 n

92 STRATIGRAPHY AND smInmmmy mms ON THE BULL- I(OUNTAIN-PEACE RIVERCANYON, CARBON CREEK AREA NORTHEASTERN BRITISH COLUMBIA (930/15, 16; 94B/1, 2)

INTRODUCTION

As the new District Geologist at Charlie lake, 1982 fieldwork was orientedtoward gaining a grasp of theregional and loc,slstratigraphy andsedimentology of thecoal-bearing sequences in the Northeast Coal- field. In thisregard I am indebted to Dave Gibsonand Con Stott of the GeologicalSurvey of Canada, Paul Cowley and NormanDuncan of Utah Mines Ltd.,and Charlie Williams of Gulf Canada ResourcesInc. for informative discussions.

Fieldwork was concentrated in the area betweenBullhead Mountain on the east andPardonet Creek on the west (Fig.27). lhis areaincludes coal licences of Utah Mines Ltd.,Gulf Canada Resources Inc.., Shell Canada ResourcesLimited, andCinnabar Peak Mines Ltd.Recently published paperson the area includethose of Gibson(19781, St.ott and(Gibson (1980), andAnderson (1980).

There are two coal-bearingformations in the area, theGething Formation of theBullhead Groupand theBickford Formation of thme Minnes ,:roup. The GethingFormation overlies the Bickford Formation and is sepsrated from it by the Cadomin Formation,which is variablypebbly sandstone to conglomerate (see stratigraphic column, Table 1). Regionallythe Cadomin Formation may rest on unitslower in the succession than the Bickford.According toStott (1973) this is due to an unconformitywhich progressivelytruncates underlying strata in a southwest-northeast direction.

TABLE 1. SIWLIFIED STRATIGRPPHY OF THEMiNNES ANDBULLHEAD GROUPS (UPPERJWASSIC+CWER CRETACEOUS) IN THE BULLHEADMOUNTAIKPARDONET CREEK AREA

BuIGething Formationlhead bal measures &CUD Cadomin Formation Pebblysandstone, quartzitic sandstone,conglomerate

Mlnnes BickfordFormation Carbonaceousmeasures Grou p Monach FormtionFeldspathic sandstone, minor mounts of quartzite

battle Peaks Formation Interbedded sandstone and shale

bnteith Formatlon @per quartzites Lower greysandstones,, teldspathlc sandstones

93 ?he stratigraphy of thearea is notyet satisfactorily resolved (D. F. Stott,personal communication). Problems include:

(1) Identifyingthe Cadomin Formation in places where it is a sandstone ratherthan a pebblysandstone or a conglomerate. It is difficult todistinguish the Cadomin Formationwhere it overliessandstone of formationssuch as the Monach. (2) Iateralfacies variations within formations of the MinnesGroup. (3) lbe natureof the unconformity at thebase of the Cadomin Formation. Does it haverelief and hence control the thickness and distribution ofthe Cadomin?

The CarbonCreek basincontinues to be a focusof these stratigraphic difficulties. Forexample, coal measures initially identified as Gething Formation were temporarilyre-interpreted to beBickford Formation by Stott andGibson (1980).

STRATIGRAPHIC SETTINGOF THE CADOMIN POPJWTION

A number of sections were examined inorder to establishthe stratigraphicsetting theof Cadomin Formation in the area. These are summarized as follows (see Fig. 21 forlocation): RidgeSouthwest of MountMonach C oa l measures Gethinq Formation Gethinq measures Coal Thickunits of pebbly quartzitic Cadomin Formation sandstone;local siltstone and recessivebeds Gradationalcontact ? Salt-and-peppersandstone, siltstone Bickford Formation (calcareous),mudstone, carbonaceous shale,coal M a ssive flaggy sandstoneflaggy Massive Monach Formation BattleshipMountain (tributary to CarbonCreek on west side) C oa l measures Gethinq Formation Gethinq measures Coal Thickunits ofsandstone to pebble Cadomin Formation sandstone,local recessive interbeds Contactcovered Massivequartzitic sandstone, salt- Monach Formation and-peppersandstone East of CarbonCreek Road andCarbon Lake C oa l measures Gething Formation Gething measures Coal Pebblyquartzitic sandstones, Cadomin Formation quartzitelocally at base, coal Contact sharp Salt-and-pepperto quartzitic Monach Formation sandstone, minoramounts of burrowed siltstone

94 (4) BullheadMountain - west side P ebb ly sandstone,Pebblyconglomerate Cadomin Formation Contactsharp Feldspathicsandstone (flaggy), salt- Monach Formation and-peppersandstone, kaolinitic quartzite bed neartop Interbeddedfeldspathic sandstone, Beattie PeaksForma.tion burrowed siltstone,black mudstone plartzite, minoramounts of black MonteithFormation mudstone,feldspathic sandstone, dark greysandstone

The Monach, Bickford, Cadomin, andGething Formations are exposed .in the 'Whiterabbit'licence area of Gulf Canada ResourcesInc,. and inridges extendingsouthwest and west of buntbnach. They comprisethe e,?mtern limbof a major syncline. The BickfordFormation is severalhundred metres thick andgrades into the Cadomin over a width of about 5 metres. An interbed of salt-and-peppersandstone, typical of the Bickford Forma- tion, lies abovethe 10-metre thick basal, sparsely pebbly quartzitic sandstoneof the Cadomin Formation.Nineteen kilometres to thenortheast, on the east sideof the CarbonCreek syncline, theBickford Forma- tion is missing. mere the pebbly Cadomin Formationabruptly overlies a burrowed siltstone (marine ?). Off CarbonCreek Road, cm the west side ofBattleship Wuntain, it rests on flaggymassive sandstone units (Monach Formation ? ) .

Eitherthe Bickford Formation develops a marinesandy facies eastward or it is truncated by theregional unconformity described by Stott (1973). Rocks inthe anticlinal structure near bunt Rochfort arid bunt Wrigley may holdthe key. Just west ofthe core of the anticline on the west sides of the two mountains, a thin zoneofBickford Fsrmation may be exposed. On a ridgenorthwest ofbunt Wrigley, Paul Cowley OE Utah MinesLtd. (personalcommunication) describes a carbonaceousmudstone, siltstone, andsandstone sequence that underlies salt-and-pepper (to quartzitic)sandstones of the Cadomin Formation. HoWeVE!r, pebblysandstone belowand withinthe sequence makes it unclearwt.ether it is all Cadomin or whetherboth Cadomin andBickford Formations are present..

East of the CarbonCreek basin at Bullheadbuntain the Cadomin is separated fromunderlying mottled (bioturbated ?) quart.zite by s,everal centimetres of coal(the contact is exposedonly on thesouth side of the mountainalong the hydro line). Below this are feldspathicsandstones, a shalytransition zone, and quartzite. The feldspathicsandstones correspondto either the Monach Formation or a sandyupper facies of the BeattiePeaks Fbrmation. The transitionalsequence below consists of interbeddedquartzite, black shale, burrowed mudstone, feldspathic sand- tone,and ferruginous shale. It is probablythe Beattie Peaks Formation. Thissequence grades downward into thickquartzite beds of the Mclnteith Formationwhich are in rathersharp contact with underlying dark grey

95 sandstones(also Monteith Formation). These darksandstones crop out at the base ofBullhead Mountain on both its west andsouth sides.

At BullheadMountain the Cadomin Formation is in part conglomeraticand locally more than 200 metres thick(Stott, 1973). Stott alsodescribed 30 metres ofconglomerate at the mouth ofCarbon Creek. At Rattleship Mountain,however, only one 10-metre bed was pebblyand the total thicknessof the formation is at most 200 metres. Inthe Mount Rochfort-Mount Wrigley area the Cadomin is predominantlysandstone. Its appearance is notdistinctive and it wasmapped as part of the Monach sandstone. As a consequence,pebbly sandstones that are stratigraphically much higher(in theGething Formation), were mislabelled as Cadomin. Southwest of Mount Monach the Cadomin is apparentlythick (400 metres ?) butonly sparsely pebbly (maximum clastsize 2 to 3 centimetres). Clearlythe Cadomin Formation is not a simple westwardthickening and coarsening fan of fluvialsediment. A local isopach map, distribution of paleocurrentflow directions, and maximum clastsize are requireddetermineto what controls its thickness and lithology in theBullhead Mountain-Pardonet Creekarea.

TRACE F'OSSILS

Some ratherspectacular examples of tracefossils are evident in the Beattie PeaksFormation along Carbon Lake Road. Abundant verticalpipe- like burrowsup to 3 centimetres in diameter are present as well as vertical20-centimetre-deep U-shapedand steeplyinclined rhizocorallium burrows(U-shaped and spreite-filled). They are particularly well developedin a number of regressive,coarsening upsequences (shale- sandstone). The structures correspond to theSkolithos facies of Seilacher(1967) and represent suspension feeders found in the shallowest parts of thesea.

PEACE RIVER CANYON

A section was examined starting at the toe of the dam and continuing alongthe north shoreto Gething Creek. It hasbeen previously described by Stott(1973), McLearn (1923), and others. The first 57 metres of the sequence atthe toe of the dam includes three thicksandstone units and is assignedto the Cadomin Formation by Stott. These unitsare gritty at thebase, fine upward,and are ripple cross-laminated at thetop. The middlezone has extensive convoluted bedding. The units all have a sharp flat base and two of thethree are marked by inclinedinterbedding of sandstoneand shale at thetop and coal at thebase. These features sugqestthe sandstone bodies may represent distributaries of thelower or transitionaldelta plain rather than fluvial channels of theupper delta plain. Foraminiferaindicating marine influence were collected by Chamney (in Stott, 1973)from finersedimentary rocks between the sandstoneunits but according to Gibson (personal communication) the work requires re-examination. The overlyingGething Formation sediments are

96 predominantly a monotonous,repeated sequence of sandstone, horizontally interbeddedshale, and coal. Interestingfeatures do include some channelstructures, lateral accretionbedding (indicative ofmeandering), minor upward coarseningburrowed sequences (bay fills ?), andCoal- boundedcrevasse splay deposits.

Variousfloral and faunal collections have been made from theGething Formation inthe Peace River Canyon.They includedinosaur bones and trackways,pelecypods, foraminifera, spores, andremains ferns,of cycads,and conifers. The writer recentlycollected a Well-pKeSeKVed silicified tree trunkin the east side of thecanyon in .view of the dam. The trunkmeasures about a metre indiameter and a mt?tre inheight. Growth rings are well preservedand alternating thin

REPERWCES

Anderson, R. B. (1980): CarbonCreek - Geologyand Coal :Resources,Paper presented at Symposium on Northeast Coal, February 1'380, 27 pp. Gibson, D. W. (1978) : Stratigraphy andSedimentology theof Iawer CretaceousGething Formation, 'Carbon Creek Coal Basin, Northeastern British Columbia, Inst. Sed. & Pet. Geol., internalcept. McLearn, F. H. (1923) : Peace River Canyon Coal Area, Geol. Surv., Canada, Summ. Rept., 1922,Pt. B, pp. 1-46. Seilacher, A. (1967):Bathymetry of Trace Fossils,Marine Geology, Vol. 5, pp. 413-429. Stott, D. F. (1973) : Lower CretaceousBullhead Group bt?tween Bullmoose Mountainand Tetsa River, Fbcky WuntainFoothills, Northeastern British Columbia, Geol. Srv., Canada, Bull. 219, 228 pp. Stott, D. F. andGibson, D. W. (1980): Minnes Coal, NortheasternBritish Columbia, Currentin Research, Pt. C, Geol. .%rv., Canada, Paper 80-1C. pp.135-137.

4 97 "z-

I ,.1.A. :

98 INTRODUCTION

The underground mineofMosquito Creek Gold Mining Co~npany Limi.ted is locatedineast-central British Columbia 2 kilometres west ofthe historic mining town of Wells at latitude 56 degrees 6 rdnutesnorth and longitude 121 degrees 36 minutes west. me Ministryinitiated this field projectin May, 1982 inresponse to the general revival of inte.cest in precious metals in British Columbiaand the renewedmining and exploration activity in the Wells area.

The specificobjectives of theproject are:

(1) lb document structural and stratigraphiccontrols of themineralized zonesand to identify potential marker horizons that could be useful inexploration programs.

(2) lb sample onerepresentative ore zone and its hostrocks for study of theirpetrographical andgeochemical characteristics.

(3) To collect samples for fossil andradiometric studies to determine theage of hostrocks, metamorphism,and mineralization.

HISTORY AUD PREVIOUS WORK

Prospectorsdiscovered the first placer golddeposits inthe region duringthe winter 1860.of Sincethen production has been virtually continuous. Several majorplacer operations were activeduring the 1982 season; many are reworkingold placer leases withmechanized mining equipment which enables them to reach deeper Tertiary gravel beds that were inaccessible to earlyminers.

Hardrockmining started at theCariboo Gold plartz mim in 1933and at IslandMountain mine in 1934. wart from a four-yearshutdown during the war, Cariboo Gold plartz mine operateduntil 1959and IslandMmntain mine until 1967. Ihe latest undergroundoperation began in 1980with the openingof the Mosquito Creek mine.

Sutherland Brown (1957,p. 10) reviewed the extensive early geological work inthe region. Since that tulletin, major studies undertaken in the area include two unpublished summary reports by Campbell(1966, 1969), radiometricstudies ofprecious metal deposits inthe cordillera by Andrew (1982)and Andrew,Godwin, and Sinclair (thisvolume), and a continuingprogram of regional mappingby Struikof theGeological Survey of Canada(1980. 1981a. 1981b, 1982a, 198213). Carlyle(in press)

99 100 produced a geologicalreview of theMosquito Creek mine for a fieldtrip tothe mine in May, 1983before the annual GAC/MAC/ZGU meeting in Victoria.

Sutherland Brown (1957)provides the mostcomprehensive descripti-on of mineraldeposits in theregion. For detailed information about the MosquitoQ-eek, Island Mountain, and Cariboo Gold plartz mines, the reader is referredto Carlyle (inpress), Wnedict (1945), and Skerl (1948)respectively.

REGION= GEOLOGY

A simplifiedgeological map of the Wells area is presented on Figure 28. The region is dominated by a thick,highly deformed sedimentary sequence o f distinctiveof quartzites, conglomerates, grits, siltites, slates, phyllites,marbles, limestones, dolomites, amphibolites, and meta- tuff (?). mom fossilstudies Struik (1982b) ascribes an Upper Paleozoic ageto the overall sequence. He assigned a Mississippianage to rocks of the Baker member in theMosquito Creek mine based on anuncertain correlation ofmine stratawith a crinoidallimestone in thenorthwest corner o f hisof map-area. Earlier,Struik (1981b) reported conodonts of Pennsylvanianto Lower Permianage from a bioclastic 1ime:;tonebed in the Rainbow member.

The sedimentarysequence has been folded and regionally~netamorphosed to greenschistfacies. Small amounts of fineeuhdral pyrite are dissemin- atedthrough most of therocks. Struik (1981a) inferred that the main foldingevent took placebetween mrlyJurassic and Late Cretaceous time fromstratigraphic and structuralrelationships throughoutthe region. Andrew (1982)obtained a Lower Jurassic(179t8 Ma) wholerock K/nr date for a sample of phyllite from theCariboo Gold plartz mine. It is interpreted to be a metamorphicdate.

Regionalfolds trend northwesterly andareoverturlled toward the southwest,with dips ranging between 40 and 55 degreesnortheast. An importantfeature of thisfolding is therhythmic devel.opment of minor folds down thelimbs ofthe main folds. In the mine areathese drag foldsplunge 21 degrees atnorth 40 degrees west tonorth 50 degrees west;they host the majority of theore zones.

LOCAL GEOU)(;Y

Figures 29 through 32 illustrategeological relationships in the Mmquito Creekmine. In the mine workingsonly the upper pact of thepale- colouredMississippian (?) Eaker member and thelower part of thedark- colouredPennsylvanian to Lower PermianRainbow member areexposed.

101 ......

IO2 Ihe identificationof many exposuresof graded bedding in bothBaker and Rainbow rocks was a key factor in establishingstratigraphic 'tops.' Mostgraded layers are less than 10 centimetres thickbut individual beds are up to 2 metres thick. The gradedbeds generally cmsist of basal fine-grainedwhite buffto quartzite that grades upward blackto phyllite. Minor fine carbonategrains occur in bothzones and the phyllitedisplays coarse rhombic dolomite crystals. The orientation of these bedsindicates that the mine strata are overturned.

Workingson Level 3 ofthe mine expose a distinctive bed that is well up inthe Rainbow member (unit 7. Fig. 30). The bed lies about 60 metres stratigraphically above the Fainhow-Baker contact and consists OE dark greyish green, fine-grained,massive faintlyto laminated rock. with abundantfine pyrrhotite lamellae and rare scattered coarse pyrite crystals. Whilethe euhedral pyrite is interpretedto be metamorphic, thedistinctive pyrrhotite texture is thoughtto he prima:ry. Ihe rock is tentativelyidentified as metamorphosed tu€€.

Lensingout of sedimentary strata made identification ofkey marker beds in the mine workings difficult.Virtually all lithologies are correla- tableover short distances but few are continuousover the entire 500- metre lengthof the mine workings.Potentially useful units are: ore- hostinglimestones, thin-bedded white quartzites, and orange to buff- weatheringdolomite layers. All threelithologies are r(sadi1yidentifi- able,even in intenselycleaved exposures. On Level ;I (Fig. 3Cl) drag folding and intensefaulting obscure the probable continuity of these beds near thesoutheastern limit of the mine wrkings. Any ofthese markerscan he used as a prospectingguide in exploration programs in the area, and other units may proveuseful locally.

Mine scale structuralfeatures are illustrated on Figure!: 29 throu.gh 32. Several minorfolds were notedwith anaverage plunge of 21 degrees towardnorth 45 degrees west. Orientation of strata c,n Figure 31 was determinedfrom many well-exposedlithological contacts that strike north 50 degrees west withdips averaging 50 degreesnortheast. Cl.eavage variesconsiderably in both orientation and intensity. Its devel.opment rangesfrom negligible to locally so intensethat cleavage obscures rock texturesand causes poor drill core recovery. Cleavage orientation roughlyparallels the strike ofrock strata butdips are shallower, rangingfrom 0 to 50 degreesand averaging 30 degreesnortheast. The orientation ofcleavage closer to horizontalthan the dip of therock stratasupports the conclusion of overturnedfolds inthe mine area. Prominentlineations throughout the mine parallel minor fold axes.

Faults ahound in the mine. Most fall into two categories:north-south- striking,steeply east-dipping dextral faults (Fig. 383), andshallow, normal faultsparallel to thecleavage (Fig. 31). The latter are abundantbut often subtle, with little or no gouge.Benedict (1945) discusses them in some detail;they produce a limitedbut repetitive displacementwhich produces an overall apparentdip of 70 degreesnortheast inthe mine strata (Figs. 31 and 32).

103 L J

LEGEND

STRATIGRAPHY SYMBOLS

RAINBOWMEMBER SULPHIDEMINERALIZATION AND SERlClTE ALTERATION BLACKAND GREY CLASTIC SEDIMENTS REPLACEMENTMINERALIZATION ...... - I1 R BAKERMEMBER QUARTZVEIN: BARREN, MINERALIZED ...I I e \\ E (51PALE, THIN-BEDDED CLASTIC SEDIMENTS SERlClTESCHIST ZONE...... S

GREYLIMESTONE GEOLOGICAL CONTACT...... -_I..

)31PALE MIXED CLASTIC SEDIMENTS FAULT ...... aGREY LIMESTONE STOPE...... :“.:3E... .. (1( CONGLOMERATE HOLE..DRILL DIAMOND ...... /

Figure 31. Geologicalcross-section of the No. 2 Crosscut West, No. 2 Level,Mosquito Creek Gold mine.

104 MINERALIZATION

Gold oreoccurs in a large number of discrete,relatively small deposits along a totalstrike length of 45 kilometresthat includes the Mc'squito Creek,Island Mountain, and Cariboo Gold plartz mines (Fig.29) (Sutherland Brown, 1957).lhese occurrences consist of either auri.ferous pyritein quartz veins in the Rainbow member (Fig. 33) orstratabound, massiveauriferous pyrite lenses, termed'replacement ore,' within and at thecontacts of limestonebeds of the Baker member (Fig. 31 ). puartz Vein Ore

The mine rocksare cut by numerous generations of intersectingquartz veins;the majority are barren. A minority of theseveins carry coarse pyrite which is invariablyauriferous. Ore-bearing quartz veins carry up to 25 per cent pyrite andgrade up to 70 grams goldper tonne, a:lthough averageproduction grades are considerably lower. Ore veins in W)squito Creek mine reach 5 metres in width; the ultimatelength and height ofthe near-verticalveins is still to be determined.

Minerhlizedquartz veins occurred in all three of themajor mines at Wells. At Cariboo Gold plartz, where totalproduction was 1.54Inillion tonnesgrading 13.4grams goldper tonne from1933 to 1959 (Carlyle, in press),the quartz veins were the main sourceof ore. At MosquitoCreek mine,during high metal price cycles, productionhas come front three quartzveins with grades ranging from4.5 to 7.9grams gold per tonne. Thesemineralized quartz veins at MosquitoCreek mine occurwithin Baker member rocksand accessory minerals in theveins are ankerite, ,galena, sphalerite, and sericite. However, Skerl (1948)also reports free gold, cosalite,argentite, and chalcopyrite from quartzveins at Cariboo Gold puartz mine. Figure 33 is a sketchof a majorquartz vein at 13ariboo Gold plartz mine. It shows thatthe vein is mostextensively developed in Rainbow rocks kut where thevein system continues into Baker member rocks it intersects andterminates in a 'replacementore' lens.

Sericite frommineralized quartz veins at Cariboo %old plartz and MosquitoCreek mine hasyielded Late Jurassic/Farly Cretaceous K/AK dates of 141f5 (Andrew,1982) and 139 5 (G. Klein, personalcommni.cation) respectively, from sitesroughly 4 kilometresapart.

Replacement Ore

The historic term 'replacementore' is usedfor the stratabound massive pyriteore lenses despite its geneticimplications. While quar-tzvein ore is most ahndant in Rainbow rocks and onlyrarely occurs in Baker rocks,replacement oreoccurs only within Bakerrocks. Typically, replacementore lenses occur within orat the contacts of thelimestone lenses(Figs. 30 and 31). The orelenses generally OCCUK within 25 metres of the contactbetween dark Rainbow member bed:jand pale Baker beds.

105 I

1 06 In additiontothis lithologic association, most of thereplacement lensesarestructurally controlled. The massivepyrite lenses are commonly locallized in thecrests or noses ofthe minor folds and less frequentlyin fold troughs. However, significanttonnages of orealso occur in steeplydipping limbs of the main foldstructure and in flat-lyingtabular lenses where the limestoneshave 'rolled out' or flattened.

At Island Mountainmine ore lenses rangedfrom 500 to 35 000 tonnes,and averaged 2 000 to 7 000 tonnes.Typical dimensions are 2 to 3 metres thick, 6 metreswide, andfrom 30 to many hundreds of metres 1on.g down plunge.Replacement ore zones have average cross-section areas 10of square metres, necessitatingtight exploration drill spacing and careful study of peripheralalteration features in ordertorecognize 'near misses' in drilling.

The pyritelenses are fine-grained andusually massive. Locally they displayfaint banding parallel to the host strata. The finestqrained pyritecontains the highest gold values. overall grades from 30 years of production at Island Mountainmine averaged 16.5 grams gcld per tonne and 2.4' grams silver per tonne (Carlyle, in press). However, grades from replacementore alone, which supplied roughly60 per c!ent ofth.e production,averaged 23.0 grams goldper tonne and 3.4 qrams silver per tonne.Overall grades at MosquitoCreek to December, 1982 mine averaged 14.5grams gold per tonne from 49 940 tonnes of quartzvein and replacement orecombined.

Ore lenseshave sharp hangingwall and footwallcontacts; 1aterall.y they gradeprogressively into coarser barren pyrite with coarse arsenopyrite, minoramounts of disseminatedgalena, sphalerite and rarepyrrhotite, theninto silicified limestone, sericitized limestone or sericite schist. The hostrock is alwayslimestone; dolomitized, silicified, or sericit- izedlimestone; or sericite schist. In the schist, pervasiveserlcitiz- ationhas obliterated the original lithology. One small replacementore occurrence in sericiteschist host rock is illustrated on Figure 31. Comparison with ore lenses in sericitized limestone suggeststhat the schistsare derived from limestoneaswell. Carlyle (in press)noted thatsericitization is most intense in thestructural footwall of the pyrite lenses.

Short (2 to 4-metre), narrow (lessthan 5-centimetre) ,veins of massive galenaand sphalerite mineralization occur in thehangingwall oriented at rightangles to the ore lenses; similar veins occur, but are rare, in the footwall. Minoramounts of turquoise-greenchromium-bearing mariposite characterizethehangingwall alteration zones. Recognition theseof alterationfeatures and peripheralaccessory minerals theat mine enlarges'targets' for exploration diamond drilling.

Some quartzveinlets show crosscuttingrelationships that clearly postdatethe ore, but at least onemajor vein may becont.emporaneous with a massivepyrite lens. In an excellentexposure in the 2E st-ope at

107 L

Figre 33. Pian of the 19-2 stope veln system, Carlboo Gold Quartz mine (after Sker I, 1948).

108 MosquitoCreek mine, a verticalZaetre-wide barren quartzvein pene- tratesthe massive pyrite lens andterminates abruptly atthe hangingwall contactwith sericite schists. me lateralmargins of this massive white quartzvein areinterlayered with stratiform silicified galena- sphalerite-pyritemineralization which gradeslaterally into fine-grained massive pyrite of typical replacementore.

GENESIS

Carlyle(in press) describes the three main genetictheories ofmineral- izationdeveloped since miningoperations began in 1933:

(1) Metalswere remobilized from the country rock during regional metamorphismand were reconcentrated in dilationzones, such as, fold axes. (2) Hydrothermalfluids rose from a deeplyturied source along a complex fracture network of quartzveins and preferential1.yreplaced the limestonebeds. (3) Fiydrothermal fluidsrose from a deeply hriedsource upthe major north-strikingfaults and preferentiallyreplaced limestone beds. plartz veinore then developed outward from the replacement ore lenses.

Recentlydeveloped metallogenic concepts of volcanic exhalative .and/or sedimentaryexhalative deposits were consideredfor this area but neither ofthe models fits well withobserved data such as: quartz vein mineralization in thestratigraphic hangingwall; atypically high gold/base metal ratios;trace metal associations of arsenic,bismuth, tungsten; and Late Jurassic/EarlyCretaceous radiometric dates for the quartz vein ore which contrast with Carboniferous fossil dates of thehost rock.

Lead isotope analyses reported by Andrew, et al. (this volume) provide a Pb/Pbmodel age of 185t50 Ma forthe lead mineralization which covers a broadenough range to becontemporaneous with regional metamorphism (K/Ar ageof 179t8 Ma) or withpost-tectonic magmatism (K/Ar aqeof 143t14 Ma) (Pigage,1977). Andrew, et al.have concluded thatthe lead, and by inferencethe gold, in thesedeposits was derived frm crustalrocks either by lateralsecretion during MiddleMesozoic regional metamorphism or by hydrothermalleaching related to Late Jurassic/EarlyCret.3cems post-tectonic magmatism.

Giventhe distribiltion of all the known golddeposits over a 45-kilometre strikelength along a singlefold limb, a regionaltectonic control for the mineralizingevent seems necessary. The writerenvisages the gold- bearingfluids were derived from thecrustal rocks during regional metamorphismand emplaced late in thetectonic cycle during a periodof fault readjustment(-140 Ma). The fluidspenetrated the folded, overturned

1 09 strata,precipitating mineralized quartz veins and reactingwith carbonate beds when encountered.Fluids flowed along dilatant fold noses and troughswithin the limestones, precipitating in massive sulphide lenses.

EWLORATION

Successfulexploration in theregion has been based either on direct prospectingor on drillingnear the critical Rainbow-Baker contact. Trenchinghas always been an essential part of the exploration programs becauseslopes throughout the area are steep and glacial overburden is deep.

The usefulness ofgeophysical methodssuch as IP, EM/VLF-EM, and SP is limitedbecause trace disseminated pyrite is ubiquitous,carbon content is highin some strata, major faultzones are frequent, and typical orebodiesare very small. A test inducedpolarization survey at Mosquito Creekmine delineated the contact between the Baker member and thehighly carbonaceous Rainbow member. Resolution was sufficientto show dis- placementof the contact along by a majornorth-south fault. More useful results were obtainedin a recent VLF-EM survey on thebsquito Creek mines property where the Rainbow-Baker contact is delineated by bands of adjacenthigh and low anomalousvalues that follow the contact and show the same north-southfault displacement. The advantagestheof VLF systemover the IP technique lie in speed, simplicity, and lowercost. Correlation of filtered VLF results withproperty geology suggests that the anomalous VLF-EM lows ortroughs may coincidewith subcropping non- conductivelimestone units.

Geochemical soilsurveys in theregion have produced gold anomalies and arsenic,lead, bismuth, silver, and copperare being used as pathfinder elementsto avoid the problem of redistributed placer gold in the glacial till. Unfortunately,chemical metal dispersion, thick glacial overburden,soil creep, and small targets make spottingfollow-up diamond- drillholes difficult. Follow-upanomaliesof by trenching would probably be ascost-effective as drilling.

On a mine scale, systematic explorationfor replacement ore at the MosquitoCreek mine involvesestablishing a regularspacing of explora- ationcrosscuts off the main southeast-northwestdrift (Fig. 30) and a regularpattern of inclineddrill holes from eachcrosscut (Fig. 31). Thistight drill pattern is essentialbecause ore zones and their alterationhalos are small. Once ore is intersected, it is developed by miningalong the plunge of thehosting minor folds (Fig. 29).

The explorationpotential for moreof these relativelysmall, but high gradegold deposits is excellent.Surface andunderground exploration programs at MosquitoCreek mine havediscovered additional reserves of replacementore. Substantial reserves had beenestablished at depth in theIsland Mountain mine when it closedin 1967. Production from the

110 CaribooCold @art2 mine was predominantlyfrom quartz vein ore j.n the Rainbow member (Figs. 29 and33) while the existence and potential of the replacementore within the Baker memberwas unrecognized. The mineral potential of minorlimestone horizons within the Rainbow member rockshas yet to be evaluated. collcLusIolus

The Cariboo Gold Belt is one of the majorgold producing regions of the CanadianCordillera. 'Ihe tbsquito Creekmine produces ore from numbera ofdeposits that are distributed along the strike extension of ore- bearingstrata that yielded 37 697 kilograms of goldand 4 354 kilograms of silversince underground mining commenced in thearea in 1933.

The many oredeposits of thebelt occur in a structurallyover-turned metasedimentaryrock sequence of theCarboniferous Cariboo Group.Mwer Jurassicregional metamorphismproduced greenschistfacies mineralogy. Deformationproduced regional, northwest-trending overtu:?ned folds: with associatedrhythmically spaced minor folds. Early 0:etaceous lower gradequartz vein ore deposits are hosted predominantly in thedark carbonaceousrocks of the Pennsylvanian/Permian Rainbow member. Higher gradereplacement ore deposits are hosted within and at the contacts of alteredlimestone horizons in thelight-coloured Mississippian Baker member. The replacementore deposits are localized by parasitic, minor folds and the crests andtroughs of thesefolds may becontinuously or discontinuouslymineralized for many hundreds of metres down plunge..

The oredeposits are clearly epigenetic although the exact mechani.sm of their emplacementhas still to determined.be The gold was likely derived from deepercrustal rocks.

The Cariboo Gold Eelt offersexcellent exploration potential within, between,and beyond the existing mine workings. An effectiveexploration program in this environment should combine detailed prospecting and geological mapping withsoil geochemistry and VLF-EM geophysics.Initial work shouldbe followed by anaggressive trenching program. The gradeof replacementore lenses and their orientation is so uniformand predict- ablethat mining can be initiateddirectly from a subcropexposure OK a singledrill hole intersection.

ACKNU?L~ENTs

The writer thanksthe manager, R. R. Yarjau, and staff of MosquitoCreek GoldMining Company Limitedfor their generous and willing. cooperation. L. W. Carlyle, mine geologist,provided extensive discussion:; and excellentillustrations of many aspects of the mine stratigraphy and ore deposits.

111 This work hasbenefitted from discussionswith L. C. Struik, J. Kelly, D. G. MacIntyre,and M. Guiguet.John Mawdsley and Mike Fournierably andcheerfully assisted in the field.

REFERENCES

Andrew, A. (1982) : A leadIsotope Study ofSelected Precious Metal Deposits inBritish Columbia, M.Sc. thesis,University of British Columbia, 80 pp. Benedict, P. C. (1945):Structure Islandat Mountain Mine, Wells, British Columbia, C.I.M., mans., Vol. 48,pp. 755-770. Campbell, D. D. (1966) : Potential Oreof Reserves andProduction, Cariboo Gold plartz Mine, Wells, British Columbia,unpub. company rept., 28 pp...... (1969) : SurfaceExploration and Production Potential of Cariboo Gold plartz Mine, Wells, British Columbia,unpub. company rept. 24 pp. Carlyle, L. W. (in press): Geological Summary of theMosquito Creek Gold Mining Company Limited, inField Guides to Geologyand Mineral Deposits, Victoria 1983Annual meeting, GAC/MAC/CGU. Hanson, G. (1935) : Barkerville Gold Belt, Cariboo District British Columbia, Geol. Surv., Canada, Mem. 181, 42 pp. Pigage, L. C. (1977) : Rb-Sr Dates forGranodiorite Intrusions on the Northeast Marginof shuswapthe Metamorphic Complex, Cariboo Mountains,British Columbia, Cdn. Jour. Earth Sci., Vo1. 14, No. 7, pp. 1690-1695. Skerl, A. C. (1948):Geology ofthe Cariboo Gold partz Mine, Wells, British Columbia, Econ. Geol., Vol.43, pp. 571-597. Struick, L. C. (1980) : Geology of theBarkerville-Cariboo River Area, CentralBritish Columbia, Ph.D. thesis,University of Calgary, 330 pp...... (1981a): Snowshoe Formation,Central British Columbia,in CurrentResearch, Pt. A, Geol. Surv.,Canada, Paper 81-1A. pp. 213-216...... (1981b): A Fe-examinationofthe Type Area of the Devono- MississippianCariboo Orogeny, Central British Columbia, Cdn. Jour. Earth Sci., Vol. 18, pp. 1767-1775...... (1982a): Geol. Surv., Canada, O.F. 858, Map Series...... (1982b): Snowshoe Formation(19821, Central British Columbia, inCurrent Research, Pt. B, Geol. Sbrv., Canada,Paper 82-1B, pp. 117-1 24. Sutherlandmown, A. (1957):Geology of the Antler Creek Area, Cariboo District, British Columbia, B.C. Ministry of Energy, Mines & Pet. Res., Bull. 38,105 pp.

112 TELKWA COALFIELD, WEST-CENTRAL BRITISH COLUMBIA (93L)

By J. KW

INTRODUCTION

The 'Pelkwa Coalfield is situated a few kilometressouthwest of TeWm and 18 kilometressouth of Smithers in west-centralBritish Columbia. The CanadianNational Railway line and Highway 16 runthrough the town of Telkwa tothe port of PrinceRupert, 370 kilometres west of the Telkwa Coalfield,

Afterthe initial discovery of coal about 1900 until the1950's, exploration hadbeen concentrated on the coal seams exposedalong the valleys ofthe Telkwa Riverand Goathorn Creek (Dowling, 1915; Bl.sck, 1951) (Fig. 34). Telkwa coalmeasures crop out only in a few valleysthat have cut deeplythrough the thick overburden. Volcanic or intrustve rocks underlie mostof the higher ridges around the Wlkwa Coalfield. Ihe Telkwa basin lies near the southernboundary of Rowser successocbasin north of Skeena Arch withinthe Intermontane Eelt of theCanadian Cordillera (Tipper andRichards, 1976; Carter, 19811,and the Telkwa coalwasures comprisepart of a Mesozoicvolcanic and sedimentary sequence cut hy graniticintrusions of Late Cretaceous and EarlyTertiary age.

In 1969,Canex PlacerLtd. conducted a drill program toexplore the northernpart of the coalfield. Since 1979, Crows Nest ResourcesLimited hasconducted an extensiveexploration program to delineate econom1.c coal seams of thelklkwa Coalfield. Mining to datehas consisted of relatively smallscale undergroundand open pit operations in theval'leys of the Telkwa Riverand Goathorn Creek. Growth in mininghas been hampered bythe limited geological understanding of the coal measures and their coal resource potential.

The present project was initiated in early August o:f 1982 with the followingtermsreference: of description of tk.e stratigraphy, structural developnent,depositional environnents, and geologic age of the Telkwa basin;the correlation of coal seams and theirquality; definition of the areal extentof the coal measures, and theirrelation- hips to surroundingrocks. This report presents preliminary restllts of thefieldwork conducted between August and September of '1982. Geological mapping,conducted at scale 1:lO 000, was basedon investigation of outcrops andexamination of drillcores. Fieldwork for the project will be completedduring the summer of1983.

STRATIGRAPHY OF THE TELKWA COAL llEAsURES

TheTelkwa coalmeasures can be subdividedinto the Iower, Middle,and Upper units(Figs. 34, 35, and 36).

113 F1 yre 34. Slnpllfled geolog of the lelkwa Coaltle16

114 UPPER UNIT i ~ I-""-----"-~ * .-

Flpre 35. GeoIogIcaI cross-sections, Telkwa Coalf It~ld

The Lawer unit consists of conglomerate,coarse tofine-grained sandstone,mudstone, and coal seams. Thisunit compriges the lower part of the Telkwa coal measures. Its thicknessvaries from 115 to 120 metres. Up to sevenfining-upward rhythmites characterize vertical sections of this unit. Each rhythmite shows a graduallithological variation up section fromconglomerates or coarse-grained sandstone through medium- grainedsandstone to fine-grained sandstone or mudstone. The individual rhythmitesvary in thickness from 4 to 40 metres.

115 116 Conglomeratesoccur in some ofthe fining-upward rhythnites, but. only nearthe base of the Lawer unit. Most conglomeraticlayers consj.st of subangularto subrounded, relatively well-sorted clasts t.hat decrease in sizeup section from cobblesthrough pebbles to granules. The conglom- eratic layersvary in .thickness from 50 centimetresto 15 metres. Most o f theof clasts originate from red,green, orgrey volcanicflows, agglomeratesand tuffs of basaltic,andesitic, or dacitic composition.

The coarse-grainedsandstones are mainly maroon, purple,or grey. They are up to 10 metres thickand similar in composition to the conglomerates. Themedium tofine-grained sandstones are purple, grey, o:c dark grey, and range up to 40 metres in thickness. The mudstones are grey, black, or brown and range from 2 to 25 metres in thickness. In the upper part of the mwer unit, mudstone layers at thetops of thefining-upward rhythmites are relativelythick. These mudstone layersare closely associatedwith coal seams. Coalifiedplant debris up to15 centimetres long, 5 centimetreswide, and 2 centimetres thickare randomly scattered within theconglomerates and coarse to medium-grained sandstones.

The Lawer unittypifies a fluvial clastic sequence. The conglomerateand commonly crossbedded,coarse medium-grainedto sandstone layers are lenticular in shapewith limited lateral extension,and represent relativelyhigh-energy channel deposits. The fine-grainedsandstones and mudstonesform laterallyextensive layers and represent relative1.y low- energyflood plain deposits.

TheMiddle unitconsists of 90 to 140 metres of medium tofine-grained sandstonesand mudstones. This unit comprises .the midd1.e strata of the Telkwa coalmeasures. 'Ihe rocksare green, grey, orblack. Theyform relatively thick and laterallyextensive layers. Some of thelayers are upto 100 metres thickand over 1 kilometre long in lateralextent. Locally,the Middle unit contains several 2 to 20-metre-thickfining- upwardrhythmi tes. Fachrhythmi te beginswith medium-grained sands tone andends with fine-grained sandstone mudstone.to Although these rhythmic sequencesrepresent fluvial deposits, localshallow marine incursionsin the Middle unit arealso signalled by the nolluscanfaunas thatinclude brachiopods.

The Upper unit consists of more than 330 metres of sandstmes, mudstones, and coal seams. This unit comprises the upper strata of the Telkwa coal measures. The lower part of thisunit consists of up t:o 180 metres of medium fine-grainedto sandstones, mudstones, andcoal seams. This successionconsists of up to eightfining-upward rhythmi.tes that change frommedium-grained sandstone throughfine-grained sandstoneto mudstone andcoal seams. Individual rhythmitesare 10 to 30 metres thick. Coalifiedplant debris up to 5 centimetresacross are conmonly sca.ttered within the sandstones. The upperpart of thisunit is more than150 metres inthickness, consisting ofmudstone with subordxate amounts of fine-grainedsandstone and marl. The rocks are greenish greyor dark grey.

117 The &per unit is a fluvialclastic sequence consisting of rmch finer grainedsedimentary rocks than those theof Lower unit.This unit representsrelatively low-energy,recessive fluvial deposits.

Plantfossils are relatively abundant, and occur mainly in the Lower and Upper units. Hacquebard, et dl. (1967)identified these fossilplants anddetermined them to beof Iower Cretaceousage. Concretions up to a few metresacross are common in iron andcarbonate-rich rmdstones and sandstonesof the Telkwa coalmeasures. Clay rip-ups, loading, slumping, flasers,convolution, thin laminations, scour filling, and bioturbation arealso common in mostrmdstones and sandstones of the coal measures.

Erosionstripped off mch ofthe *per and Middle units in placesfrom the Telkwa Coalfield(Figs. 35 and36). Overburden ranges in thickness from fewa metres to more than100 metres outside major valleys in the coalfield.

HAZELTON VOLCANIC ROCKS

The Telkwa coal measures unconformably overlie a volcanicsequence composedof red, purple, green,greyor flow and pyroclasticrocks (Figs. 34,35, and 36). Tnesevolcanic rocks are of dacitic, andesitic, orbasaltic composition. me contact is clearly an unconformitythat is marked by basalconglomerates or coarse-grained sandstones of the Telkwa coalmeasures that lie on theuneven, erosional surface of the volcanic sequence. Similarvolcanic rocksoccur outsidethe Telkwa Coalfield. They are of Lower Jurassicage (Sinemurian to earliest Pliensbachian)and comprisepart of the Howson subaerialfacies of the TelkwaFormation, a lower stratigraphicunit of theHazelton Group (Tipperand Richards, 1976).

BULKLEY INTRUSIONS

A majorintrusion of porphyriticgranodiorite and quartz monzonite cuts thecoal measures at the north endof the Telkwa Coalfield (Figs. 34 and 35). This stock is oneof the wper Cretaceous (70 to 84 Ma) Eulkley intrusions(Carter, 1981). Elsewhere, the coal measures are also cut by upto 1O-metre-thick quartz porphyry dykes which are similar in composi- tionto the majorintrusion, and by up toZ-metre-thick mafic dykes of unknown age.

STRUCTURAL FRAMEXORK

The Telkwa coalmeasures dip mostly 5 to 15 degreesto the northeast or east(Figs. 34 and35). However, faultingcauses local variations due to dragfolding or block tilting. These faults dip mostly at high angles

118 rangingfrom 70 to 90 degreesand strike northwest,east-west, north- south, OK northeast. Some createdintensely brecciated and sheared zones upto 5 metres wide that commonly containbrecciated andsheared coal seam blocks. The high-anglefaults show reverse or norma:t displacements ofup to 30 metres (Figs. 34 and35). Mafic dykes intruded along some of thenorthwesterly faults, and all maficand felsic int.cusionsare at least partlyfault controlled. The mfic dykes are int:enselysheared and,locally, are altered to talc schist.

The coalmeasures appear tobe bounded by a number of northwesterly trendinghigh-angle faults that are parallel to faults wi.thinthe coalfield. The net displacements on theseboundary faults appear to he mainly vertical andrange from 50 to 300 metres. 'Ihe Tekwacoal hasin has a horst and graben confipration that consists of two .:>aralkl, major grabensthat contain coal measures separated bya central.horst made up ofHazelton volcanic rocks.

COAL SEAMS

The coalin the Telkwa basinoccurs in the Lower and Upp,sr units(Figs. 34,35, and 36). Coal seams, therefore, are classifie'j as lower and upper sequences.

The lower sequenceconsists of up tofour coal seams, 1 to 15 metres apart,that occur near the stratigraphic top of the Lower unit. Individlalcoal seams rangefrom 1 to 6 metres andaggregate zones from 2 to 12 metres in thickness. The lowercoal sequence extendscontinuously throughoutthe Telkwa Coalfield and varies from 2 to 40 metres in thickness.

Followinginfilling of theuneven, eroded surface of theolder Hazelton terrane by fluvialdeposits of the Lower unit of the Telkwa coal measures, an extensiveflood plain developed and bogs persisted long enough forpotentially economic coal seams to form. Periodicflooding anddeposition of river mdsoccurred. The coal swamp and floodplain environment was altered and ended by marine incursions. Sedi.ments depositedduring a few short-termtransgressions and regressions mark the end of thelower coal sequence.

The uppercoal sequence consists of up to 13coal seams. It lies .in the lower part of the@per unit. Potentially economic coal seams are closelyassociated with black mdstone layers at the tops of fining- upwardrhythmites of fluvial clastic rocks.Intervals bet:ween individual coal seams rangefrom 2 to 20 metres, almostthe thickness of individual f ininq-upwardrhythmites. Coal seams rangein individual thickness from 1 to 5 metres and inaggregate thickness up to 26 metres.

The uppercoal sequence occupies a stratigraphicinterval of 20 .to 170 metres. hridently,eutropic coal swamps andflood plains developed again in a recessive,low-lying fluvial environment, following deposition of theMiddle unit.

119 Both sapropelic and humic coals comprisethe lowerand upper coal seams. The sapropelic coal consists of black,dull canneloid type with vitrain stringersless than 1 millimetre thickand upto few a per cent of disseminatedpyrite. This coalrepresents limnic gyttja deposits. The humic coalconsists of alternatingclarain anddurain with occasionally abundantvitrain andfusain. This coal representslimno-telmatic reed moor deposits. Thelower andupper coalseams have vitrinite reflectances (% nux.)of 0.6 to 0.9 per cent. Althoughthe lklkwa coal representslargely limnic totelmatic deposits, it may alsocontain paraliccoal locally due tothe marine incursionsnear the top of the lower coalsequence and near the base of the uppercoal sequence.

Naturalburning occurred in limitedparts of some coal seams thatcrop out in thesteep cliffs along Goathorn Creek. These burnt seams occurin zonesthat lie within 10 metres of thebase of theoverburden. The sedimentarysections with burntcoal seams show localcollapse or crackle structures,red oxidation zones, melted rock fragments, and residual ash layers.

CONCLUSIONS

The Telkwa coalmeasures can be subdivided into threestratigraphically significantnap units with respect tothe potentially economic coal seams:the Lower unit,the Middle unit, and the Upper unit.

Maximum thickness of thecoal measures succession reaches 400 metres. Stratigraphic columns show typical,vertically and laterallyaccreting, fluvialclastic sequences with periodic marine incursions. The fluvial sequencesappear to comprise channel lag, point bar,braided bar, levee, crevasse-splay, and floodplain deposits.

Coal seams occur atthe upper part of the Lower unit and atthe lower part of the Upper unit. In eachunit they occur near the topsof most fining-upwardfluvial clastic rhythmites. The lowercoal seams can be tracedcontinuously throughout the lklkwa Coalfield within a relatively narrowstratigraphic interval. The uppercoal seams arerelatively thick and arebest developed in thesouthern half of the coalfield.

The coalmeasures are probably of Lower Cxetaceousage. Theyuncon- formablyoverlie Hazelton volcanic rocks, and Bulkley intrusions intrude them. The lklkwaCoalfield exists because the coal measures lie in two grabens andwere protected from erosion.

ACKNOUL~MENTS

Thanksare extended to: F. Martonhegyi, D. Handy, S. Cameron,and K. Lendellof Crows Nest ResourcesLimited and L. Gethingof Bulkley Valley Collieriesfor their willing cooperation, and I. Webster forhis able assistance. The authorthanks his colleagues in theGeological Branch fortheir helpful support in variousaspects of thisproject.

120 REPERENCES

Black, J. M. (1951) : Report Goathornon Creek Coal Area, B.C. Ministry of Energy, Mines & Pet. Res., Ann. Fept., 1951, pp. A291-AZ97. Carter, N. C. (1981): Porphyry Cbpper and Molybdenum Deposits, west- CentralBritish Qlumbia, B.C. Ministry of Energy,,Mines & Pet. Res., Bull. 64, 150 pp. DoWling, D. E. (1915): Coalfields of British Columbia, Geol. Surv., Canada, Mem. 69, pp. 167-189. Hacquebard, P. A., Birmingham, T. F., andDonaldson, J. R. (1967) : Petrography of Canadian Coals Relationin mvironmentto of Deposition,Energy, Mines & Res., Proc. of Symposium on the Scienceand Technology of Coal, MinesBranch, Ottawa, pp. 84-97. Tipper, H. W. andRichards, T. A. (1976): JurassicStratigraphy and History of North-CentralBritish Columbia, Geol. arv., Ci~nada, Bull. 270,73 pp.

121 LEGEND

QUA RTZ-FELD SPAR PORPHYRY SYMBOLS PORPHYRY QUARTZ-FELDSPAR

:PORPHYRITIC GRANODIORITE DIAMOND-DRILL HOLE ...... -

=QUARTZCONTACT, GEOLOGICAL PORPHYRY APPROXIMATE ...... """.1oeoa DIORITE FAULT, ASSUMED...... 3VOLCANIC ROCKS

(GEOLOGY AFTER COMPANY PLANS]

Flqre 31. Geoloq of Porphyry Creek prospect.

122 PORPHYRY CREEK PROPERTY ( 94D/8E)

By T. G. Schroeter

INTRODUCTION

On August19th and 20th the writer visitedthe Porphyry Creek molybdenum property (MI 94D-113) locatedapproximately 20 kilometressoutheast of Johanson Lake. '&e property was beingdrilled by Getty Mj-nes, Limited in an optionagreement with Teck Corporation. Wcess was by helicopter from JohansonLake.

GEOLOGY AND llINERALIZATION

Molybdeniterosettes and pyrite occur on fractures and in quartz veinlets withinmlti-phase dioritic to granodioritic intrusive rocksand host TaklaGroup andesitic rocks, which locally are hornfelsedand contain red garnet,epidote, and pyrite (Fig. 37).Magnetite is locallyabundant and chalcopyrite is rare. The stockhas been mapped along a northwesterly trendfor 750 metres and is 250 metres wide. Alterationminerals include quartz,potash feldspar, sericite, epidote, and garnet.

Drill hole 81-3 was deepenedfrom 242.9 to 457.2 metres andhole 82-6 was drilledto a totaldepth of748 metres, bringingtotal 'I982 drilling to 962.3 metres.

The writer acknowledgesthe hospitality of GettyMines, Iimited and Bema IndustriesLtd. during his visit to the property.

123 LAY CREEK PROPERTY (94D/9E)

Qv T. G. SchrOeter

INTRODUCTION

The Lay Creekproperty, consisting ofthe Breccia claims (60 units total), is locatedapproximately 6 kilometres east ofthe south end of JohansonLake, 210 kilometresnorth-northeast of Smithers. kcess tothe property is either by the Omineca Mining Road 170kilometres from GermansenLanding or approximately 200 kilometres via fixed wingwheel or float-equipped aircraft fromSmithers. A 2.5-kilometreroad connects the showingswith the OminecaMining Road. The writer visitedthe property on August20th.

GEOLCGY AND UINERALIZATION

Two min areas of surfacemineralization and a thirdgeophysical target were tested by diamond drilling with three drill holes totallingapproxi- mately 425 metres. The Rreccia zone trends in a northwesterlydirection apparentlyfor a continuouslength of 320 metres; dips range from35 to 50 degreessouthwest. The breccia is unusualin that it has a bedded or sheetednature wherein anFpllar thin plates to massive slabs of andesitic, dioritic, andpyroxenitic rock sit in a matrixof rhodochrosite, quartz, and chlorite with erratic clots and veinletsof chalcopyrite, pyrite, and minoramounts of magnetite.Chalcopyrite is also disseminatedinthe dioriticfragments.

The Contactzone occurs at thecontact between granodiorite and breccia andcontains chalcopyrite disseminated in granodiorite.Secondary minerals includemalachite and azurite. There is also a distinctive orange-redamorphous 'stain' which is anomalous in copper.

The writer acknowledgesthe hospitality of Silver Standard Mines Limited andLornex Mining CorporationLtd.

124 TOODOGGONE RIVER AFSA (94E)

By T. G. Schroeter

INTRODUCTION

TheToodoggone River area is situatedapproximately 300 kilometres north ofSmithers (Fig. 38). Access to the area was by aircraft,mainly from Smithers.

The writer spent two weeks in the area, mainlynorth of the Toodoggone River. work includedfill-in geological mapping using a 1:25 000 scale topographicbase, as well as detailedproperty examinations and core inspection.Particular attention was paidstructuralto controls, alterationzones, and mode and types of mineralization.

In addition, Andre Panteleyevand Larry Diakow conducteddetailed strati- graphicstudies in the area (see accompanyingreports, this vo:.ume). It is hoped that a preliminary map ofthe Toodoggone area will he available in thespring of 1983 at a scale of 1 :50 000.

WORK DONE

The following diamond drilling was completedin the Toodoggone during 1982:

(1) Kidd Creek Mines Ltd. (a) JD 1 445 metres (4 739 feet) (b) PorphyryPearl 498 metres (1 632 feet) (c) Al 1 667 metres (5 469 feet) 3 610 metres (11 840 feet)

Core from this program was briefly examined.

(2) SEREM Ltd.Approximately 3 597 metres (11 800 feet) of underground andsurface drilling on theAmethyst gold breccia zone (Lawyers property).

Core from this program was not examined.

(3) IdcanaMining Corporation. Drilled 621 metres (2 0:38 feet) on the Metsantangold breccia zone.

Core from this program was examined.

(4) Ih Pont ofCanada Exploration Limited. Approximately 915 metres (3 000 feet) was drilled on a 'new'(upper) quartz: vein at Eaker mine. Tbtal drilling in the area was 8 743 metres (28 678 feet.).

Core from this program was notexamined.

125 FI yre 30. Toodoggone map-area.

126 TOOOOGMNE RlYEK AREA, MINERAL PROPERTIES M)I No. Claim Naw YE operator NO. Claln Name operator I Aura ------SEREM Ltd. 44 Ed0 1-4 Du bnt Erp I. 2 hers 1-4 """ SEREM Ltd. 45 Metsantan1-9 Lacanaulnlng 3 Audrey 1-2 """ KIdd Creek Mlnes 46 Pot 1-3 vu mbntE>~I. 4 Audrey4 East, Audrey 22 Kldd Creek Mlnee 41 Met3 1-2 Talga Cons. mst 48 AI 1-8 KlddWeek Mines 5 Kern 1-9 """ Kidd Creek Mloss 49 mr KB""C0 6 New K-rs 1-2 21 Ksnnco 50 Scree 1-3. bo58 1-3, Kldd Week MlneS 1 Rat 25 Comlnco Ltd. &I,JO, J0 JR, 8 Wmnqranted cialm 12.13, 14 Domlnco Lid. McClolr 1-5, plus 9 Atty """ Taiga Cons. fractlmI 10 FlreLtsel 2 SEREM Ltd. 51 Air 1-2 vu mnt EWI. 11 Flrel-3 """ Vu PontEml. 52 Poo, on, LO", OXlde SEREM Ltd. 12 RICh """ Taiga Cons. 53 Bile 1-2 ~a~gamns. I3 hx 57 Can1 nm Ltd. 54 lbose 1-4 s. Y""Q 14 Fin 1-9 16 WlOCO 55 Brt, &ole, Wlnkle, Kldd Week. Mlne5 15 &ace 1-4 11. 48, 49 0. MacOlarrle Bul I, Chute, 16 hlgo 58 Cominco Ltd. Slrprise. carom, 11 RN 3. 4, 5 YlndeTraMlner Oscar Fr., Wankle

18 Pra. hl. kaPUlC0, 3, 4. 5 SEREM Ltd. Fr., htoine LOUIS, Gotch 1-2 Tour Sturdee. 019 19 Jock 1-5 8 Taiga Cons. Blrd, Kadah, Aodee, 20 Gossm 1-2 8 Lacma Mlnlng RJ Fr., JP Fr. 21 Jock 1-5 8, 39 SEREM Lfd. 57 GWP 1-43. bvgk 22 %a* 50 lntarnatlanalShasta Bear 23 SI lver Ped 45. 50 C. Kaal I 58 Gordon iBvIe5. Gordon 24 Pili """ Davlss 2 25 Wmda """ 59 eaves 1-4 ti7 eeatWBsteTn mt. 26 Nlb Movntaln 63 ltsch60 """ SEREM Ltd. 21 Orange. kys 1-4, 28, 29. 42 61 mrcuIes. llt~as SEREM '4 Ltd.. kg 1-2, OJ 1-4 62 Star, Ca, Sun 58 SEREM Ltd 28 To No. 2 """ Wich63 - -. .-" SEREM Ltd.. 29 WP 200 1 64 Roo 1-6 13, 14 R. nong 30 Golden Nelghbour 1-4, 31 65 Mm 1-2 Nenant E@.

""" NevnontElpl. Canp, Caw Fr., Jol ly 66 *np 1-2 mger, ktfui Dodger 61 Golden Llon 1-2 ".". Nenanf Elpi. 31 Sanders 40 Taiga Cons. 68 CBX 1-12 """ Ta I 98 Con 5. 32 GWP 43 """ @eat mrtm mt. 69 Cia* 46 Umx 3 4 Chappelle34 26 Du Pont E?@. 70 %nos 1-4 """ Lacana MI ling 3s pel 26 0" Po"+ &$I. 71 5u" I-2 "."_ N""+ ExpI. 36Warn-granted cldlm 27 0. McDonald 12 hodah2 """ SEREM Lfd.. 31 New Lawyers 1-4, Law 64 SEREM Lfd. 13 Pipe "."_ Kldd Reel< Mines """ KI dd Cree< ne3 1-3. U~eeze,Road I- 14 %earn MI 111. mrry 1-2, wson 15 ksap """ Q~~T~as-ern mt. 1-2, GTW 1-3. plus 16 Silver Llon """ thmont Eml. fractlonr 11 Golden Llon 3 """ Nemnt ExpI. 38 Cuke 1-2 SEREM Ltd. 18 byez 1-4 """ WwmontExpi. "_." 39 To No. I """ Du bnf Eml. 19 Golden Llon 4 Nemnt Erpl. 40 MU1 1-2 52 Du Pont Eml. 80 Castle Mtn., Castle """ rqnam1c 01 I CO. 41 SIIver Pond, Sliver 11 Geat WesternPet. Mtn. Fr. Creek, Sliver Peak, 81 Foghorn ------Kldd Creek Mines Sllver Glzziy 82 Leghorn """ Kldd Week Mlnes 42 Kodah 11 83 Axesons """ Kldd Creek Mines 43 Lars 1-4

127 I

x.. ': ...... z .+:2 :; J 14 gE E.??uz

128 GEOLOGY

The regionalgeological setting is discussedinGeological Fieldwork, 1981(Ministry of herqy, Mines andPetroleum Esources, Paper 1'382-1, pp. 122, 123).

PROPERTIES

JD (MI 94E-32)

Sixteendiamond-drill holes were drilled byKidd CreekMines Ltd. to test theSchmitt and Carbonate breccia showings on the JD claim (see Fig.39). A quartz-hematite-sulphidezone varying in width from approximately 1 to 4.6 metres was tracedalong a 600-metre strikelength (105 degrees). Dips were northinto the hill andvaried from 23 degrees at the west end to 50 degrees at the east end. me mineralizedzone is open to the east but is cut off to the west by a series of northwesterly and northeasterly trendingfaults near the Schmitt showing. A persistent gougezone was intersected on thefootwall, andminor quartzstringers were locatedin thehangingwall. The mineralizedquartz structure cccurs within a sequenceofmassive, green to maroon hornblende-feldsparporphyritic- andesiticflows and tuffs of the modoggone volcanic series. Locally, there are tuffaceousagglomerates and volcanic breccias. Alteration mineralsinclude hematite, chlorite, manganeseand Dxide.Gangue mineralsinclude amethystine to white quartz, calcite, andminor amounts ofbarite. Sulphideminerals include pyrite, chalcopyrite, acanthite, galena, and sphal.erite.Approximately 100 metres tothe southeast anotherstrong quartz vein structure was traced by hand. trenching. It may bean offset of the JD 'vein.'Native gold was recovered from this zone.

PORPHYRYPEARZ. (MI 943-31 )

Two drill holes were completed byKidd CreekMines Ltd. near the junction of Moosehornand WClairCreeks (see Fig. 38). Pyrite,galena, sphalerite, and chalcopyriteoccur as disseminations,fracture fil.lings, and in quartztcarbonate +anhydriteveins within a hypabyssalmonzonite which has been altered in varying degrees toK-feldspar and sericite.

GOLDEN FURLONG

Two holes were drilled by Kidd Creek MinesLtd. to test a fault- controlled zoneof intenselysilicified andkaolinized andesitic tuffs. The zonecontains native gold in associationwith hematite (see Fig.38). Finelybanded pyrite with traces of chalcopyrite were found in quartz- richzones which reach 35 metres inapparent thickness. Drusy, open cavitieslined with quartz and/or hematite were common.

5 1 29 SYMBOLS IIAMOND-DRILLHOLE. INCLINED ...... W lRENCH ...... - 4TTITUDE ...... 25 :AULT.ASSUMED ... .-

GALENA

*BARITE MALACHITE

ANDESITIC TUFFS

200 -IC*L~~M~II~~ LFTER COMPANY PLANS)

Flgure 40. Settlng of the Alberts Hump area.

RIDGE

Two diamond-drillholes were completed by Kidd Creek Mines Ltd. to test a highlyaltered structural zonelocated approximately 4 kilometres east along anopen grassyridge from Alberts Fiump (see Figs. 38 and 40). Andesitictuffs havebeen altered to quartz,chlorite, and hematite. Barite is a common ganguemineral. Sulphides encountered included pyrite andgalena.

BONANZA

Six diamond-drillholes were completed by Kidd Creek Mines Ltd. to test the BOnanza zoneand its relationship to theRidge zone, which adjoins to thesoutheast (see Figs. 38 and 40). Andesiticash tuffs have been

130 alteredto quartz, chlorite, and hematite.Malachite, azurite, pyrite, chalcocite,chalcopyrite, and sphaleriteoccur within silicified zones. Locally it appearsthat the pyrite was introducedas a fine-grained 'front', and lithicfragments havebeen replaced by pyrit.e.Chloritiza- tion offragments is common.

ALBERTS HUMP

Two drill holes werecorrpleted by Kidd Creek Mines Ltd. to test a large zone of quartz *alunite +_ kaolinite alteration in andesitic to d,acitic hornblende-feldsparcrystal and lithictuffs (see Fig.381, Altered zones contain many wggysections. A hypabyssalintrusion was encountered at depth.Pyrite was the main sulphidemineral encountered.

METSANTAN (MI 943-64)(Geological Fieldwork, 1981, Paper '1982-1, pp.131, 132)

The Metsantanprospect is located on thesoutheast flaric of'Metsantan Mountain. ' Illring1982 Lacana Mining Corporation colrpleted five diamond- drillholes on theMetsantan gold breccia zone (see Fig. 41). A weak quartzstockwork zone with minoramounts of galena,sphalerite, chalcopyrite, and pyrite mts crystalto lithic tuff which is locallyper- vasivelyepidotized, especially feldspar crystals and 1i.thicfragments.

GOLDEN LION

TheGolden Lion prospectsare located scuth of Claw muntain,near the headwatersof DedeeyaCreek and northof Abesti Creek (see Fig.38). During1982 Newmont Explorationof Canada Limitedconducted surface exploration on thislarge group ofclaims. On Golden Lion 1 claim, a zonetrending 155 degrees has been traced 2.5 kilometrtzs.Malachite, galena,sphalerite, pyrite, and chalcopyriteoccur in a gangueof quartz- hematite-barite. The zonehas been traced in talus and apparentlyhas a widthof 10 metres. The host rocks are 'Toodoggone' airfallhornblende- feldspar crystal to lithic tuffs.

On the Golden Lion 3 claim, a 600-metre by 75-metrealteration zone trends 340 degrees.Alteration minerals include quartz, hematite, and variousclays (alunite ?). Brightgreen fluorite moccurs, but no sulphides were observed.

LAWYERS (MI 94E-66) (Geologicalfieldwork, 1981, Paper 1982-1,p. 130)

Undergroundand fill-insurface diamond drilling by SEREll Ltd.continued to define anddevelop ore zones on the LawyersAmethyst gold breccia zone (see Fig.38). In addition,the Cliff Creekbreccia zone was eqlored byextensive surface trenching along a northwesterlylength of approximately 1 000 metres.Locally, spectacular zones with amethyst were encountered.

131 0" DDH 5

Figure 41. Settlng of thebtsantan property.

I32 BAKER MINE (MI 943-26) (GeologicalFieldwork, 1981, Paper 1982-1, pp. 129-132)

Miningcontinued at a rate of90 tonnes per day on the A vein. A limited diamond-drillprogram conprising approximately 915 metres was undertaken to test a newly discoveredquartz vein just north of A ve.in.

MOOSEHORN (Geological Fieldwork,1981, Paper 1982-1, p. 132) hlring 1982 Great WesternPetroleum Corporation conducted a detailed chip samplingprogram on their Moosehorn prospect (see Fig. 38).

MOUNT GRAVES (GeologicalFieldwork, 1981, Paper 1982-1, p. 132) hlring 1982 Great WesternPetroleum Corporation conducted a detailed chip samplingprogram on their Mount Gravesprospect (see Fig. 38).

A” A”

The writer acknowledges the hospitality and logistical support offered in thefield by thefollowing conpanies: KiddCreek Mines Ltd., Bema IndustriesLtd., Eu Pontof Canada ExplorationLimited, SEREM Ltd., Central MountainAir Services Ltd., Airlift Corporation, Iacana Mining Corporation, Newmont Exploration of Canada Limited., and Kelowna Flightcraft Ltd.

Schroeter, T. G. (1982): Toodoggone River(94E), B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1,pp. 122-133.

133 A COIQARISON OF VOLCANICSTRATIGRAPHY, STRUCTURE, AND EYDROTHERWAL ALmTION OF T€E SILVER POND (CILILKl CREEK) AND URICH-AWESOME CLAIM GROWS, -DOGGONE RIVER (94E) By L. J. Diakow

INTRODUCTION

The'Toodoggone Volcanics'comprise a northwest-trendingbelt at least 90 kilometreslong and 15 kilometres wide, located 300 kilometresnorth of Smithers. They are anEarly Jurassic, predominantly subaerial, calc- alkalinesuite probably deposited inanisland-arc environment. The regionalstratigraphic section includes a base of andesiticflows which interfingerwith and areoverlain by flows and pyroclasticrocks of andesiticto dacitic composition (Panteleyev, 1983, this volume). Silver andgold, principally as argentite and electrum(Schroeter, 1981), occur in discordantquartz veins and grosslystratabound stockworks. On the other hand,pervasive siliceous zones which arestratiform and stratabound appearto contain only minor amounts of preciousmetal mineraliza- tionalthough erratic high values are common. The veinand stockwork occurrenceshave sharp boundaries andnarrow alterationhalos; con- cordantsiliceous zones are diffuse with extensivewallrock alteration characterized by clay minerals, alunite, and barite.

Figure 42 Locatlon map for the Si lver Pond (Cloud Creek) andWrich-Awesom occurrences.

134 mis researchaddresses the problem of distribution and variabilityin morphologyandwallrock alteration of these two types of silica occurrences by analysinq two occurrences. Thewrich-Awesome, which representsthe vein and stockworktype, and Silver Pond (CloudCreek), a pervasivesiliceous zone (Fig. 42). Each area was mapped at '1:5000. Approximately150 hand specimens of altered rockand 58 chipsamples of siliceousrock were collected. lhe siliceoussamples are currently being analysedfor 16elements including gold and silver; alteration assemb- lages are being defined by x-rayanalysis.

Thisresearch constitutes part of a graduatethesis currently in progress at theUniversity of WesternOltario; it is supported in part by the Ministry of Energy,Mines and Petroleum Resources.

FIWre 43. Alteratlonmineral zoning in the SI lver Pond (CloudCreek) area.

135 SILVER POND (CLOUD CRlmK) AREA

LOCATION AND GENERAL GEOLOGY

The Silver Pond (cloudCreek) occurrence (Silver Pond, Silver Sun, silver Creekclaims) is approximately 2 kilometres west of the Lawyers prospect. It is a 5-kilometre-squarearea of low reliefthat is underlain by por- phyriticandesite with subordinate interbeds of lithiclapilli tuff and agglomerate.Attitudes measured from tuffaceousbeds strike consistently northeastwith dips of less than 20 degreesto the northwest. Exposures ofagglomerate occur in onlyone faultblock that is on thesouth-facing slopes immediatelynorth of Cloud creek.

The area is segmented by a network of faults whichacted as channelways forhydrothermal fluids. Dykes of syeniteoffset the layered rocks and are locallyaltered; perhaps they occupy early faults whichwere reactiv- atedlater to provide access to hydrothermal fluids. A freshsyenite dykedismembered by a series of en echelon faultsindicates that more more than one phase of faultingaffected the area.

ALTERATION

The Silver Pond (CloudCreek) alteration zone is circular in outlinewith a diameter of 2 kilometres. A number of isolated'patches' of intermediate-advancedaryillic alteration and silicification occupythe central zone.Alteration grades laterally into an outer propylitic zone (Fig. 43).

INTERMEDIATE-ADVANCED ARGILLIC ZONE

In this zonesecondary quartz, clay minerals, sericite, and alunite replace primary minerals in porphyriticandesites. Where micro- crystallinequartz is mostabundant there are low-lying mounds of undeterminedthickness that are up to 150 metres by 50 metresin size. Inthese mounds theoriginal porphyritic texture of theandesite is almostcompletely obliterated; only outlines of relictfeldspar phenocrysts and biotitecrystals remain. Pyrite is rare,occurring as fine, disseminatedgrains in quartz.Barite commonly occurswith quartz as crystalaggregates lining cavities or as irregular greasywhite clots up to 3 centimetresacross.

A recessive zone partiallyto completely encloseq all siliceous occurrences.Typically these rocks arewhite with yellow-orangesurface oxidation,display a remnant porphyritictexture, and are composed almost entirely of clayminerals. Dickite, kaolinite, montmorillonite, and illite arethe primary constituents; alunite and sericiteare subordinate. The stratiformnature of 'white' rockswith co-spatial pervasive silicaoccurrences suggests that a temporalrelationship exists. lhis relationshipmight bedue inpart to primary bed porosityin underlying

136 tuffs that enabled fluid movement alongthe base and through fractures in theporphyritic andesite. Red staining is imparted by hematite and goethite; commonly brillianthues of irridescentgreen andblue occur on fracturesurfaces.

A youngerphase of silica emplacementformed discontinuous veins up to 2 centimetres wide thatconsist of terminatedquartz crystals and lesser chalcedonicquartz. They cutboth white rocks and syenit".

PROPYLITIC ZONE

Thischlorite-carbonate-epidote alteration zone is widespreadand extends beyond theboundary of the mapped areaat Silver Fund. Inthe transi- tionalarea betweentheargillic and propyliticzones plagioclase phenocrysts show signs of corrosion and alterationto white chy and calcite, and amphibole is commonly replaced by chlorite,.Fine-grained, disseminatedpyrite andmagnetite are ubiquitous within this transitional area,but each rarely constitutes more than 3 per cent of therock,

Oxidationof pyrite and magnetite occurs throughout the alteration system butdoes not appear topenetrate deeply into the rocks. Further, in areas of propyliticchlorite-carbonate-epidote alteration, intensive 'bleaching'and replacement of therock by clayminerals is absent,,These observationssuggest that the broad patterns of alteration observed in theSilver Pond areaare hypogene.

LOCATION AND GENERAL GEOLOGY

The Wrich-Awesome area is 25 kilometressoutheast of Baker minesite betweenAttycelley meek and Finlay River(Fig. 42). Panteleyev(1982) presented a compilationof the regionalgeology south (of FinlayRiver. The geologyanddistribution of known quartzstockwork and vein occurrenceswithin thestudy area are shown on Figure 44. Porphyritic andesiteflows with interveningbeds of crystal lithic tuff underliethe majority ofthe mapped area. These rockscorrespond with pante.teyev's map unit 5b andgrade upward into quartzose tuffs that are similar to the overlyinggrey dacitic ash flow tuff (unit 6, Panteleyev,1982). Takla Grouppyroxene basalt, limestone, and chertcrop out along the western marginof the map-area. A faultrelationship between mkla and'modoggonevolcanic rocks is indicated.mkla chert beds outli.ne chevron-style foldswith amplitudes up to 7 metres andmost mklamcks dip :steeply northeastas opposed to shallow westward dips in thenearby 'Ibodoggone rocks.Takla rocks are also exposed in a fault-bounded wedge directly north ofAttycelley meek. Coarse-grained quartz monz(mite is ,exposed where the overlyingmodoggone rocks have beenremoved hy erosionin the northernpart of thearea.

131 Figure 44. rSology and distribution of silica occurrences in the Wr i ch-Awesons area.

I38 ALTERATION

A tabular,discontinuous zone characterized by silicification and clay minerals is alignedsubparallel to a majornorthwest-trending fault zone (Fig. 44).plartz stockwork and vein occurrences designa.ted by numbers 1 and 2 on Figure 44, formnarrow subvertical zones containing individual veinsthat are up to 4 centimetres wide inbrecciated trachyandesite. Quartzin the veins occurs mainly as clear terminatedcrystals; there are lesser amountsof amethystine quartz, Chalcedonic silica, which is white or tinted to shades of red and green by hematiteand chlorite, forms bandedveins that crosscuttheolder, clear quartzveins. Calcite commonly fillsvoids within the clear crystallineveins.

A tabularzone on the Wrich claims (3on Fig. 44), approximately 100 metres wide, is outlined by pale,clay-altered porphyritic rocks and confinedto a fault-bounded area. The pale colour of theserocks reflectsreplacement ofphenocrysts and matrix material in the host andesite by a mixtureof white quartz and clay minerals. X-ray analysis showed thatthe white rocks contain kaolinite and mnor amounts of pyrophyllite(Panteleyev, 1982). Widespread hematite and limonite impart a rustycolour to outcropsurfaces.

The quartz-kaoliniteassemblage grades outward into a larger zone characterized by chlorite-calcite-epidote-pyritealteration. This propyliticassemblage characterizes the entire trachyandesite unit and alsooccurs in the greydacite. In the area mapped, .zhe intensity of alteration decreases away from faultzones suggesting that it is fracture controlled.Pyrite occurs as fine-graineddisseminations in the altered rocks; it averages 1 to 2 per centgenerally but exceeds 5 per cent withinone-half kilometre of intrusiverocks that lie to thenorth. Fine-graineddisseminated magnetite is also present in trachyandesite and dacite.'Reddening' of feldspar phenocrysts is a phenomenon that becomes morepronounced adjacent to veinand stockwork occurrences in the area. It might be caused by albitization and oxidation of magnetite or it might be alteration to K-feldspar.

MINERALIZATION

Theonly mineralization observed in the Wrich-Awesome areaoccurs within a narrow shearzone in greydacite at location 4 on Figure 44. The occurrenceconsists of blebsof galena in a gangue of quartz,chlorite, epidote,and pyrite. Although this occurrence is small, it is important because it representsone of only two known mineralizem3occurrences in thegrey dacite map unit.

SUnnARY

Hydrothermalfluids apparentlytravelled along fractured zones and alteredsurrounding volcanicrocks to produce two dj.stincttypes of

139 silicaoccurrences in the Toodoggone belt.In the Wrich-Awesome area, quartzstockwork veins are related to a northwest-trendingfault zone thatappears to be an important control for silica-kaolinite-pyrophyllite and, to a lesser extent,chlorite-carbonate-epidote-pyrite alteration. In Silver Pond (CloudCreek) area zones of silicification and kaolinite- dickite-alunitealteration appear to be localizedatthe base of a relativelyflat-lying porphyritic andesite unit. Perhaps primary bed porositygoverned the shape and distribution of alteration in thisarea.

Chipsamples from 58 sitesat Silver Pond(Cloud Creek) reveal consistently low goldvalues. Only 11 sampleshad detectable gold (greater than 20 ppb);four were inthe 48 to 55 ppb range,and one was 164ppb. The resultsare consistent with anacid-leached clay-silica capping containingthe sulphate minerals alunite and barite.Other metals show little concentration in thealtered zonewith the exception of manganese whichoccurs consistently in the 600 to 800 ppn rangeand barium from 0.15 to 0.4 percent. These values are consistentwith results for a widevariety of elementsreported by Schroeter(Geological Fieldwork, 1981,Paper 1982-1, pp. 126-128).

In the Wrich-Awesome area,four grab samples from silicified zones shown on Figure 44 givethe following results:

Au Ag wb ppm

Slte 1 (Awesome) 24 I .25 'Site 1 (Awesom) <20 c0.4 Site 2 66 60.8 Site 3 <20 6.76

A(3RNawLEWMENTS

The writer expresseshis appreciation tothe following companies for logisticsupport, discussion, andpermission to examine theirmineral prospects: Du Pont of Canada ExplorationLimited, Great Western Petroleum Corporation, KiddCreek Mines Ltd., Lacana Mining Corporation, Newmont Exploration of CanadaLimited, and SERFM Ltd.

Thanks areextended to Dr. A. Panteleyevfor his direction and helpful discussionduring the field season. Shaun Pattendenand Mitch Mihalynuk providedcheerful, able assistance in thefield.

REPERENCES

Panteleyev, A. (1982) : ToodoggoneVolcanics South of FinlayRiver, British Columbia, B.C. Ministry of Energy,Mines S Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp. 135-141.

140 Schroeter, T. G. (1981): ToodoggoneRiver, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1980. Paper 1981-l., pp. 124-1 31...... (1982) : ToodoggoneRiver, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp. 122-133.

141 Figre 45. Geology between Toodogpne and Sturdee Rivers.

142 GEOLOGY B- TOODOGGONE AND STURDEE RIVERS (94E)

By A. Panteleyev

INTRODUCTION

Regional mapping in 'ToodoggoneVolcanics' that was initiatedsouth of FinlayRiver in 1981 was expanded in 1982 tocover the central portionof thevolcanic belt betweenToodoggone River on thenorth end and Sturdee River on thesouth. During 1982, 270 squarekilometren was mapped as shownon Figure 45. The area is beingactively explored for gold-silver deposits (see report by T. Schroeter, this volume).

Field mapping data was entered on Federal 1 inchto 1/2 mile (1 :31 680) air photographs. The detailedinformation was subsequentlytransferred to 1:25 000 base maps preparedunder contract andavailable from Burnett ResourceSurveys Ltd. Final compilation was doneonFederal 1:50 000 preliminary map sheetsfor NTS 94E/2,3, 6, and 7. L. J. Diakow examined areas exhibitinghydrothermal alteration, notably silicification and clay-alunitedevelopment, as an adjunct to these regional studies., Two ofthe more economicallyinteresting zones were studied j.n detail -- the Silver Pond(Cloud Creek) zone shown on Figure 45,and the Wrich-Awesome area,south ofFinlay River. Diakow discussesboth zones in a separate report inthis volume.

All mapping by Schroeter, Diakow,and this writer will becompiled in early 1983and released as a preliminary map at scale 1:50 000.

GEOLOGY

Six major stratigraphicsubdivisions were established as sham on Figures 45and 46. The mostwidespread and continuous rock type in the Toodoggone volcanicbelt is map unit 6, 'greydacite.' Therock is distinctive in outcropand hand specimen. 'me base of thxs unit provides the most usefulstratigraphic datum planeinthe map-area. The grey dacite is alsothe only clearly identifiable rock type that provides continuitybetween the 1982map-area and the area south ofFinlay River mapped in 1981 (see Panteleyev,1982). Although other Toodoggone rocksthat underlie grey dacite (map units 1 to5) are lithologically similar northand south of Finlay River, the map unitsdescribed in this report are notstratigraphic equivalents of thosedescribed in 1981. The stratigraphic section betweenToodoggone and SturdeeRivers includes thefollowing map-units as shown on Figure 45:

Unit 1

Tuffand tuffaceous sandstone 'red beds. ' A well-layered sequence of graded,feldspathic crystal-lithic ash to dusttuffs or reworked (epiclastic) tuffs. Some coarseboulder conglomerate lenses.

143 SAUNDERS-WESTJOCK CREEK FAULTSYSTEM

Flyre 46. Dlagramticstratlgraphlc column, Toodoggone- Sturdee River area.

1 44 Unitla

Volcanicflow unit ofundetermined extent, exposed only in Moc,sehorn Creekand overlain by tuffaceousred beds (unit 1) . The flows consist of up to 15 per cent pinkalbitized plagioclase phenocrysts 3 to 6 millimetres inlength in an aphanitic, dark green matrix that contains chlor- itizedbiotite and abundantvery fine-grained magnetite.

Unit 2

Andesiteflows -- medium-grainedhornblende feldspar porphyry. Grey- green to purplish brownwhen fresh,pervasively oxidized to salmcn pink or orange in weatheredand hydrothermally altered outcrops. Sparse reddish brown apatite (?) grains to 1 millimetre in size are distinctive andcharacteristic ofthis rock type. Epidote alteration with minor amountsof associated pyrite is common. This is anex.tensive map unit derived from a homogeneous magma source. It consistsmainly of rxassive flows,although some displaytrachytoid crystal alignment. Less common is flow breccia andthere are minoramounts of pyroc1a:;tic breccia and tuff.

Unit 3

Andesiteflows and tuffs -- a heterogeneousassemblage of flow and pyroclastic rocks -- predominantlyhornblende feldspar porphyry flows and lithicash tuffs. In thesoutheast corner of the map-area grey,fine to medium-grainedcrowded porphyry flows are common. Interspersed in at least threelevels in thesuccession are quartzoselithic-crystal. tufEs that are believed to be lateralequivalents to map unit. 4. Map unit 3 appears to be a temporalequivalent of map unit 2 andprobably inter- fingers with it. unit 4

Quartzose andesite pyroclastic rocks -- an extremelyheterogeneous unit in terms ofcolour, clast size, and origin. Clasts range in size from dustto coarse blocks in brecciaand compositions cover the spectrumfrom purecrystal tuff tosolely lithic material. In detail,lava flows, breccia,agglomerate, thick crudely layered ash andb'locky ashflows, occasionalwell-bedded ash fall deposits, and some reworked (epiclastic) units make up this map unit.

Unit 5

Andesiteand trachyandesite flows -- a thin,dissected unit that caps pyroclasticrocks of map unit 4. It signalsthe endex]?losiveof pyroclasticactivity and theonset oflava eruptions,, Flows oE the bimodal suite -- andesite andtrachyandesite -- are interlayered along with minor tuffs. me volume, regionalextent, and significanceof the alkalinerocks is notcurrently known.

145 Units 5a.5b, and 5c

A basalticsequence found onlyeast ofthe major Sunders Creek-West Jock Creek faultsystem. The sequence containswell-layered ashtuffs (unit 5a).coarse-grained hornblende plagioclase porphyry flows (unit 5b), and mixed ashto coarse lapilli tuff beds (unit5c). The rocksare strongly epidotized and,where oxidized,are stained a hematitic,deep purple ochre colour .

Unit 5ai

Pyroxenebasalt intrusion -- possibly a laccolith or sill. Iherock is made upof 5 to 10 percent pyroxene phenocrysts in a matrixof plagio- clasemicrolaths. It is generallyunaltered but near the faulted western contact it is extensivelyzeolitized.

Unit 6

Grey dacite -- greyto grey-green rocks that weather dark grey to brown and form resistant, blocky-jointedscarps. The rocks containup to 25 percent biotite, hornblende, quartz, feldspar phenocrysts and abundant clasts of quartzfeldspar porphyry. No internalbanding is present in theunit but compaction, clast orientation, and locallydeveloped welding impart a weak layering-foliationto outcrops. Ihe base of the unit most commonly is a relativelyclast-poor, chloritic, devitrified, vitrophyric crystaltuff. Locally it is a coarsefragmental ash flow with abundant, rounded clasts up to 10 centimetresindiameter. This coarse pyroclastic rockprobably formed as a turbiditylag deposit that reflects turbulencedeveloped by localtopographic features along the base of an overalllaminar ash flow.

AGE OF VOLCANICS

Radiometricdates forhornblende and rubidium-strontium samples from volcanic and relatedintrusive rocks in themodoggone area range from 179 to 207 Ma (Gabrielse, et dl., 1980). A sampleof alunitehas been reportedto be190?7 Ma (Schroeter,1982). A new date of 204 Ma is the firstto be reported from biotite in modoggonevolcanic rocks. The sample of biotite-bearingquartzose crystal ash tuff was collectedsouth ofFinlay River from rocks of Panteleyev's 1981 map unit 5a.Ihese rocks are probablyequivalent to map unit 4 in thisreport. The 204 Ma date correspondsto 202and 207 Ma dates fromnearby graniticintrusions at Kemess deposit (ann and Godwin, 1980).Collectively, radiometric dates fromsouth of Finlay River to the Stikine River suggest that modoggone volcanicswere deposited over a 20-million-yearperiod from approximately 200 to 180 Ma.

1 46 Sample Data:

Sanpie NO. MaterialLocation %K ~*40 % Rad. Apparent Age Analysed Ar*40 (Ida )

81AP-TZ8 57'05'38"N81otite6.87t0.02 (3) 25.743 97.5 213427 126°39'30'lW

NOTES K determined by theAnalytical Laboratory, Ministry of Energ,Mines and Petrolem Reswrces; number in parenthesis refers to number of K analyses. Ar determination and agecalculation by J. E. Mrakal,hiverslty of tfi.tIsh Colunbla. Constants used: h = 0.581 x lO-l%r-I; h6 4.96 x 10-l%r-l; K40/K = 1.167 x

DISCUSSION

The volcanicassemblage mapped represents a subaerial,.predominantly pyroclasticaccumulation that was probablyrestricted to a relatively small island or island chain. Magma underwent little differentiation, judgingfrom the preponderance of andesitic rocks. Some differentiation took place toproduce quartzose andesitic rocksthat are transitionalto dacite.True dacite erupted only at the end ofpyroc1asti.c activitf that producedthe grey dacite ash flows. Small, probably isolated, individual magma chambersproduced localized basaltic and trachytic volcanic rocks and small intrusions. No rhyolitebeenhasfound. Hydrothermal alteration produced pale, quartz-bearing, commonly banded rocksthat resemblerhyolite. The alteredrocks, which are composedrquartzof grains,clay minerals, and alunite, are invariablylocalized in fault zones.

The greydacite is interpretedto be a massiveash flow sheet or !sheets that acted as a single coolingunit. It is at least 250 metres thick and coveredan area at least 15 kilometres by 40 kilometres. "ne volume of thegrey dacitesheet is a minimum of 125 cubic kilometres, which is equivalent to majorash flow sheets described in othervolcanic .fields (for example, see Stevenand Lipman, 1976). Compared to a.sh flows in the SanJuan volcanic region of Colorado, the grey dacite map unitranks as a 'moderate volume ash flow. '

Sites of mineralization/alteration do notappear tohave any simple lithologiccontrol although mineralization tends tofavour andesitic flowsand flow contacts with tuffs rather than pyroclastic rocks. %is is possibly a consequence of hydrothermal fhidsbeing channeled by well- defined,long-lived fracture/fault systems andesite.in contrast,In hydrothermalfluids that entered pyroclastic units became dispersed and diffused by intergranularflow in the highly porous and permeable rocks. In addition,fluid-rock interaction in andesites was minimal as opposed

147 tothe strongly hydrothermally altered pyroclastic rocks where much alteration of glassshards and crystals tookplace to produce abundant clay minerals.

Volcanic-relatedhydrothermal activity was controlled by olderfaults and fracturezones; many of thesetrend northerly tonorth-northeasterly. The alteredzones are independent of the predominantlynorthwesterly- southeasterlytrending younger faults shownon Figure 45.

A" A"

Bema Industries Ltd.provided expert expediting services from Smithers. Central MDuntain Air ServicesLtd., Airlift Corporation, andKelowna Flightcraft Ltd.provided air services. The writer acknowledgesthe courtesy and support by Ix1 Pont of Canada ExplorationLimited, SEREM Ltd.,and KiddCreek Mines Ltd. Mitch Mihalynuk and Shaun Pattenden ably assistedthe writer; Larry Diakow was a capablesenior assistant.

REFEREXES

Cann, R. M. and Godwin, C. I. (1980) : Geologyand Age of the Kemess Porphyry Copper-Molybdenum Deposit,North-Central British Columbia, C.I.M., Bull., Vol. 73, pp. 94-99. Gabrielse, H., Wanless, R. K., Armstrong, R. L., andErdman, L. R. (1980) : Isotopic Dating of EarlyJurassic Volcanism and Plutonism in North-CentralBritish Columbia, inCurrent Research, Pt. A, Geol.Surv., Canada, Paper 80-1A. pp. 27-32. Panteleyev, A. (1982) : Toodoggone VolcanicsSouth Finlayof River, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, Fieldwork, 1981, Paper 1982-1, pp. 135-141. Schroeter, T. G. (1982): ToodoggoneRiver (94E). B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp. 122-133. Steven, T. A. andLipman, P. W. (1976) : Calderastheof San Juan VolcanicField, Southwestern Colorado, U.S.G.S., Prof.Paper 958, 35 PP.

148 A COWARISON OF THEGEOLOGIC SIZTTING OF STRATIFORM llAsSIVESUIPHIDE DWOSITS OF "HE GATAGA DISTRICT WITH TEE UIDWAY AND WINDY-CRAGGY DmOSITS, NORTHEMBRITISE COLUMBIA (94F. I; 1040/16; 114P/1:2)

BY D.G. MacIntyre

INTRODUCTION

A study of the stratigraphic and structuralsetting of sediment-hosted zinc-lead-baritedeposits of theGataga district of northeastern British Columbia was initiated in 1979and continuedthrough the 1980and 1981 fieldseasons (see MacIntyre,1980a, 1980b. 1B81a,1981t1, 1982a, 1982b, 1982c;MacIntyre andDiakow, 1982). In 1982 further mapping in the Gataga district was curtailed due tobudget restraints. However,a short visit to the Driftpile Creekproperty wasmade in late Juneto emmine drillcore. The scope of theGataga project 'hasbeen expanded; it is now a regionalstudy of Paleozoic stratiform ma:;sive sulphidedeposits in northernBritish Columbia.During 1982 geologic fieldwork was done on tm suchdeposits, Midway (1040/16) andWindy-Craggy 1,1 14P/12E). If budgetsallow and suitable logistical support c,3n be obtained,additional work will bedone on thesedeposits during 1983.

Paleozoic and particularlyLate Devonian clasticsedimentary strata in northernBritish Columbiahave tremendous resmrcepotential for zinc- lead-baritedeposits. Consequently, all areas underlain by theserocks arepotentially important and will be studied t3 assessthe potential and to provide a betterunderstanding of thegeologic setting and genetic controlsfor this important class of mineraldeposits.

The purposeof thispaper is to compare and contraststratiform massive sulphide? barite deposits of the Gataga districtwith the Midwa.y and Windy-Craggy deposits. The paper will show that each of the three sedimentary?volcanicterranes discussed host distinct types of stratiform massivesulphide? barite deposits. Those of theGataga district are barite rich, occur within a linearsedimentary trough, andhave .3 very minorpre-ore volcanic component. Midway is a stratabmndsilver-rich massivepyrite-sphalerite-galena deposit within transgressiveclastic rocks and platformalcarbonates. Windy-Cragqy is a thickcupriferous massivepyrrhotitefpyrite deposit that is relatedto a.ltered basaltic volcanicrocks.

GATAGA DISTRICT

The history,geology, and mineraldeposits of the Gataga distric~thave beendiscussed in previousreports and papers(for example, VacIntyre, 1982b).Figure 47 shows thesetting of theGataga district with respect

1 49 tothe Selwyn basin andKechika "rough and Figure 48 shows locations of mineraldeposits and thegeneral geology of the district. An idealized stratigraphic column is shownon Figure 49 alongwith those for the Midway and Windy-Craggy areas.

Recentwrk by Gordey(19821, Gordey, et al.(1982), and Dawson and Orchard(1982) has helped to refinethe stratigraphy of the selwyn basin. The informalnomenclature proposed by theseauthors has been adopted for the Gataga district.That is, all rocksoverlying Kechika Group and underlyingMiddle to Late Devonian siliceous clastic rocks are included withthe Road River Group. Overlying Ute Devonian to Mississippian transgressive'black clastics' are includedwith the Earn Group. It shouldbe noted that microfossil studies are continuing and hopefully =;;;,4;HONOUS

PALEOZOIC PLATFORM =PALEOZOIC.. . BASIN i i

Figrre 41. Tectonic subdlvlslons of thenorthern cord1 Ilera and location of the htaga dlstrlct (1). the Midway (2). andWlnd/-Cragg, (3) deposlts. inset shwsrestoration prlor to 450-kl lometre rlght lateral dlsplacemnt along Tlntlna and northern Rocky Mountaln Trenches.

150 furtherrefinement of agerelationships will be possible whennew data become available. Much uncertainty still remainsabout the exact ages of stratiformbarite-sulphide deposits of thedistrict; most age:; are inferred by stratigraphic position rather thanpaleontological data.

LEGEND

-1gure 48. Gsneral geology andlocatlon of stratiformba-itesuiphlde deposits ot the Gataga district.

151 As shown on Figure 49, stratiformbarite-sulphide bedsoccur atseveral different stratigraphic levelswithin the basinal faciessuccession of theGataga district. The oldest known depositsare late Middle to early LateOrdovician age as indicated by graptoliteassemblages collected from hangingwallblack shales (identification by B. Norford,Institute of Sedimentaryand Petroleum Geology, Calgary).Both barren barite (for example,Aikie-Sika) and massive pyrite (for example, Reb) end members arepresent. The formeroccurs immediately above a quartz wacke turbidite unit and is located just outboardof the MacDonald platform; thelatter occurs within ananomalously thick section of blackshales and chertthat probably represents a relativelydeep water basin. Both depositsare overlain by a transgressiveblack shale unit. This unit diachronouslyonlaps platformal carbonates outside the district.

Stratiformbarite-sulphide deposits of Early Silurianage have recently beendiscovered by ComincoLtd. in thesouthern part of theGataga district(for example, CT and ERN prospects).Fbotwall rocks are shallow waterthin-bedded limestones, dolostones, and quartzites that are locally brecciated and mineralizedwith pyrite. Hangingwall rocks include calcareoussiltstone, shale, and chertymudstone. Mineralization varies upsection from predominantly pyrite with variableamounts of sphalerite and minor galena to mainly barite. lhe stratigraphicsuccession suggests mineralizationoccurred during an Early Silurian marine transgression that was terminated by a majorregression in Middle Silurian time. This regressionresulted in erosion of BrlySilurian and olderrocks and partialfilling of theKechika Trough with dolomitic detritus. The stratigraphicsetting ofEarly Silurian deposits in the Gataga district is strikinglysimilar to that of the Howard's Passarea of the Selwyn basin(Morganti, 1981).

The most importantstratiform barite-sulphide deposits of theGataga districtoccur within a 180-kilometre-longbelt of blackcherts, cherty mudstones,argillites, and siliceousshales and siltstones of the Middle to Late DevonianGunsteel 'Formation' of the lower Earn Group. The deposits of thedistrict can be fittedinto a Meggan-typezoning model. In this modela central,vent proximal, massive pyrite zonewith local high-gradesphalerite andgalena concentrations grades outward into massive,barren bedded barite. The Driftpile Creekand Bear deposits wouldbe examples of the massive pyrite zone, the Cirque, Elf, and MOunt Alcockdeposits appear to be atthe transition frommassive pyriteto barite andthe Kwadacha, Pie, and DPP depositsare examples of the relativelybarren bedded baritefacies. Bedsof nodularand thinly laminatedbarite at the mugh, men, Kwad, Yule, Gnome, Del, Aki, Gin, andPesika properties may be thedistal equivalents of themassive pyrite andbedded baritedeposits.

Footwallrocks for the Late Devonian stratiformbarite-sulphide deposits of the Gataga districtare typically rhythmically beddedblack cherts (porcellanites),cherty mudstonesand argillites,siliceous shales, and lesserintercalated turbiditic siltstones. These rocks represent a starvedbasin regime with periodic turbidite sedimentation. lhickness of

152 thefootwall unit varies. It is relativelythin (10 to 20 metres) in the southern and eastern parts of thedistrict where it onlapsslope and shelfcarbonates and underlies massive barren bedded barite: and laminated nodularbarite occurrences (for example,Kwadacha, Pesika, Del, Gin, Aki, Gnome, Pie, Yule, Kwad, DPP). It is relativelythick (100 to 200 me.tres) withchert-rich sections where it underliesstratiform massive badded barite-pyrite-sphalerite-galenadeposits (for example,Elf, Fluke, Cirque,bunt Alcock) andlaminated pyrite-sphalerite? barite depxits (for example,Bear, DriftpileCreek).

2 UPPER 1 SYLVESTER

LOWER SYLVESTER 3

McDAME

SD ROAD RIVER,

"i- ROADRIVER OS OR KECHIKA?

i.-:Kg;'; ...... :., .... GOG OR ATAN MIDWAY bI?l...... WINDY-CRAGGY GATAGA LEOEND

Figure 49. Stratigraphic colurms forthe Cetaga district (1). the Midray (2). and Windy- Crag9 (3) areas.

153 SURFACETRACE OF MINERALIZED @,ONE

GUN STEEL FORMATION CHERTYARGILLITE, SILICEOUS SHALE,CHERT; MINOR SILTSTONE, LIMESTONE

ROAD RIVER GROUP

SYMBOLS

SURFACESHOWING: Py=PYRITE,Ba=BARITE ......

FAULTBALL ON DOWNTHROWN BLOCK ...... -

DRILL HOLE 1979-1981 ...... +

1982 DRILL HOLE ...... "-.

Flyre 50. General geolog and drl II hole locatlons. Drlftplle Creekproperty.

I54 Siliceousto nonsiliceous pyritic black silty mudstones,argillites,, and shales form theimmediate hangingwall for the Late De.vonian ba.rite- sulphidedeposits of theGataga district. Calcareous 'nodules' and septarianconcretions are common inhangingwall rocks at Ilriftpile (Creek andthe Bear. Some of the'nodules' may be limybeds that werepulled apartduring compaction. The shalesare locally phosphatic and c'nerty andcontain silty interbeds interpreted to be distalturbidites. In general,hangingwall rocks have a relativelyhigh claistic component compared tofootwall rocks. This suggests amore open marj.ne environment withhigher sedimentation rates followed formation of thedeposits. This chanaecoincides with a major eastwardadvancing Late Cevonian msrine transgression. Much of theclastic material deposited in the Kechika Trough atthis time may havebeen derived from uplifted fault blocks to thewest (Gordey, 1982).

DRIWILE CREEK

Driftpile Creek was theonly property in the Gataga districtthat was visitedduring 1982. The following is a brief summary ofthe work done on this propertyto date. From 1978 to 1982a total of 54 drillholes werecompleted atDriftpile Creek.Approximate location of these holes relativeto the projected and known surfacetraces of the mineralized zone(s)are shown on Figure 50. The Gataga JointVenture (Welcome North Mines Ltd.,Chevron Canada Limited, Getty Mining Pacifi"Limited, and Canterra Energy Ltd.)has now earned a 50 per cent equity in the Driftpileproperty; Placer DevelopmentLimited and partners must now matchthe expenditures of the Gataga Joint Venture in orderto retain their 50 percent interest.

Drillingduring 1982 (holes 51 to 54) furtherdelineate3 a northwest- trendingmoderately east-dipping zone located approximately 300 metres east of the camp. This zone consists of laminatedpyrite withlocal high-gradeconcentrations of galena and sphalerite;minor amounts of bariteoccur at the base of thepyritic interval. The sectionappears to be upright with stratigraphic tops to the northeast. The mineralized zone is underlain by typical banded chertyblack mudstones;and siliceous argillite of theGunsteel Formation (uD%) and is overlain by nodular black silty shalesthat the author includes with thetransqressive shales ofthe Besa RiverFormation (uDMB).Both hangingwall and footwall rocks areconsidered part of theLate Devonian toMississippian Earn Group (blackclastics) following the recent usage of Gordey, et al.(1982) for the Selwyn basin.

Sparseoutcrop and structuralcomplexity have made delineation ofminer- alizedzones difficult, even with relatively close spaced drilling. High- angle normaland reverse(thrust ?) faultsare common and typically offsetearlier developed fold structures.

It is still uncertainwhether the baritic and pyriticmineralization intersectedin drilling at Driftpile Creek is partof one laterally

155 156 continuouszone repeated by folding and faulting or actuallyrepresents severaldiscrete mineralized zones at different stratiqraphiclttvels. Recentbiostratigraphic workby Dawson andOrchard (1982:' inthe Selwyn basinindicates both Middle Devonian and Mississippian (Osagean) barite deposits are present,inaddition tothe regionally extensive Late Devonian(Frasnian) barite-sulphide horizon. Apparently a similar time- stratigraphicdistribution of depositsapplies to the '3riftpile Creek area (Gordey,1982). . However, the main sulphide-bearingzone at Ilrift- pile Creek is most likelyFrasnian in age, as it is in bcNth thesouthern partof the Gataga district and MacMillanPass area of Selwynbasin.. Thin limestoneinterbeds collected from drill core at Driftpile Creek art? currently being dissolved in the hopes of findingconodonts.

MIDWAY

The Midway deposit, which is situatedwithin a broadsynclinorium of Paleozoicplatformal carbonates and transgressive clastic rocks immedi- atelyeast of the Cassiar batholith(Fig. 47), was descrj.bed in a previousreport (MacIntyre, 1982~). Regional stratigraphy is summarized on figure 49,and Figure 51 shows thegeology inthe vicinity of the deposit.

Sixdiamond-drill holes were completed on the Midway propertyat t'he end ofthe 1981 exploration program with encouraging results (Remyional Resources MWS Release, November 23, 1981);15additional holes: were drilledin 1982 (Fig. 52). lhe work done todate, whichhas been funded by Amax of Canada Limitedand Procan Exploration Company withRegional ResourcesLtd. as operator,has defined a high-gradestratabound zinc- lead-silverdeposit in a block of moderatelynortheast-6,ipping Cevonian to Mississippian carbonateand clastic rocksthat are part of the McDame limestoneandlower Sylvester Group respectively(Gabrielse, 1969). Massivestratabound pyrite-sphalerite-galena mineralization occurs at threedifferent stratigraphic levels (Fig. 52). These levels are referred to as the Lower, Discovery,and Upper zones(Stollery and Sellmer, 1982). Several pyritic cherty exhalite beds also occur in a 50- metre section of argillitesoverlying the Upper zone.

The Lawer zoneoccurs atthe top of the MiddleDevonian I4cDame lim,estone (Gabrielse,1969). lhe mineralization is mainlyhosted by thelimstone which is locallystrongly brecciated. Drilling indicates: that the Lower zone is present in a subcircular area roughly 500 metres by 700 metres in size. The zone,which is locallyvery high grade, varies in thickness from less than 1 metre in its peripheryto approximately 23 metres in diamond-drillhole 82-7 (Fig.52). Combined lead+zincqrades vary from 2.65 to 32.75 per cent with 42 to 630grams silver per tonne (George Cross News Letter, No. 188, September 30, 1982). The bt?stintersection todate is indrill hole 82-8 with 2.6 metres averaging 21.61 percent lead, 14.89 per cent zinc, and 1 371 grams silverper tonne. The lower zone is estimated to contain 2.7 million tonneswith 370 to 435 grams silverper tonne and 18 to 20 per cent combinedzinc-lead (J. Stollery,

157 personalcommunication). In addition, a weightedaverage ofcomposite results from eightdrill intersections contains 0.65grams gold per tonne, 0.35 per cent copper, 0.14 per cent titanium, and 0.11 per cent bismuth(George Cross News Letter, November 25, 1982).

The Lower zone is overlain by an upward coarsening clastic sedimentary cyclethat is approximately100 metres thick. lbe cycle is characterized by increasing frequency, thickness, andcoarseness of lithic wacke and pebbleconglomerate intercalations up section.

The Discoveryzone occurs approximately 100 metres up section from the Lower zone. The zone is well exposed by surfacetrenching (Fig. 52). The mineralization on surfaceconsists of relativelycoarse-grained pyriteintergrown with light-coloured sphalerite and lesser galena. me zone was intersected in all 1981 drillholes. Grades from1981 drill holesranged from4.24 to 9.29 per centlead-zinc with 62 to 99grams silver per tonne. The Discoveryzone apparently grades eastward into pyritic and bariticcherty exhalite.

SEE FIGURE 51 FOR LEGEND SYMBOLS

UE = UPPER PYRlTlC EXHALITE TRENCH ...... - UZ = UPPER ZONE LZ DL DISCOVERY LONE DDH LONE DISCOVERY DL ...... h LZ = LOWERZONE ROAO ...... -- "

BEDDING...... i- $?%* OUTCROP ...... -,,.A*'

MINERALIZED HORIZON...... -

- Figure 52. Geology and drill hole locatlons, Midway prcperty.

158 me Upper zoneoccurs 10 to 20 metres above theDiscovery zone. This zone,which was intersectedin 1981 drillholes, is relati.velythin (less than 3 metres) andlower grade than the Discovery and Lower zones.

Host rocksfor the Discovery and Upper zones are chertyargillites and siltyblack shales at the base of thesecond coarsening-upward sedi- mentarycycle.

Mapping inthe vicinity ofthe Discovery showing suggests that there are severalpale-coloured pyritic cherty exhalite beds in rocks over1yin.g the Upperzone (UE, fig.52). South of the Midway deposit$cherty exh.alite bedsoccur at a similar stratigraphicposition (Fig. 51); these may representthe distal equivalents of themassive sulphide zones. A primaryobjective of our 1982 work on the Midway property was to collect samplesfrom the exhalite horizons for lithogeochemical studies. Silt samples were also collected from drainagesinthe vi.cinity of the deposit,and all limestoneand chert units were sampledfornucro- paleontological work. Results will bepublished when analytical work is completed.

The panelofrocks containing the Midway deposits is separated from McDame limestone by a high-anglefault of unknown displacement. The progressive downward displacementtoward the east of the Lower zone suggests similar high-anglefaults might also bepresent: between drill holes 2 and 7, holes 9 and 18, and holes 18 and 17. Sam,? small bedding planeshear zones were alsonoted in trenches on theproperty suggesting that some horizontal movement hasalso taken place.

The Midway is a new, economicallysignificant example of! a stratabound carbonate-hostedmassive sulphide deposit that is overlain by clastic rockscontaining sedimentary-exhalative-type mineralization. Unlike deposits ofSelwyn basin and theGataga district, whichprobably formed instarved third order basins, the Midway appearsto have formed in a relativelyshallow water platformal environment. Sulphide precipitation occurredduring short-lived episodes of fine clastic sedimentation that precededperiods of coarse clastic deposition. The significan,ze to exploration is that a starvedbasin environment is notnecessary to form this typeof deposit. Probably the most criticalfactor in determining where deposits of this type are formed is thelocation of hydrothermal vents, not hostrock composition or sedimentaryenvironme.?t. Such vents areprobably located along major crustal breaks; these can occuranywhere in a basin,slope, or platformenvironment. In the case of the Lower zone at Midway, karstingof the WDame limestone pr:.or to cl.astic sedimentationmight have established favourable sites for later SUI-phide deposition.

WINDY-CRAGGY

The Windy-Craggy stratiformcupriferous massive sulph!.de deposit is locatedin the Alsek-Tatshenshini River area of theSt. Elias Mountains

159 inthe extreme northwesterncorner of British Columbia.Because of the ruggedand inaccessible nature of this area andextensive ice fields and glaciers, little is known about the stratigraphicrelationships and mineralresource potential of the various geologic units present.

Regional 1:250 000 scale mapping by Campbelland Dodds (1979)defined severalmajor fault-bounded geologic terranes within theAlexander allochthon(Fig. 47). The Windy-Craggy depositoccurs within a broad belt of volcanicand sedimentary rocks (Fig. 53) assumed to belargely Paleozoic in age.These rocks are intruded by intermediateto felsic plutonicrocks of Late Paleozoicto Tertiary age (unit MTg, Fig. 53).

I ie 138.00. I 114P/llW. 12.13.14W

Flyre 55 Generalgeolog, in the vlclnity ot the Wln&f-Craggydeposit. Ps = predominantlysedimentary rocks; Pv = predominantly matlc to intermediate volcanic rocks; DL = Devonian limestone; MTg = Mesozoic to Tertiary intrusive rocks; TS = Tertiaryclastic rocks; 1 = Wln&f

160 rn the Windy-Craggy area thestratigraphic succession, which is inform- allycalled the Kaskawulsh moup(Campbell andWdds, 19?9), consists of a lowerunit of intermediateto mafic locally pillowed flows and volcanic brecciaof unknown age(unit Pv, Fig. 53). It is apparentlyoverlain by intercalatedcalcareous andnoncalcareous carbonaceous siltstones, greywackes,carbonates, and andesitic to dacitic tuffs and flows (unit ps 1 Fig.53). Mike Orchard(Geological Survey ofCanada, Vancouver) hasrecently identified four Upper Triassic (Norian)and one Devonian conodontfauna from a thinlimestone debris flow bed that presumably occurs at thebase of this unit and inthe immediatehangingwall 'of the Windy-Craggy deposit. TheDevonian fauna is interpreted to frombe Devonianlimestone clasts inthe debris flow. A limestoneunit is presentnortheast Windy-Craggyof and contains Devonianmacrofossils (unit D~,Fig. 53).

The Windy-Craggy deposit and the Alsek (Tats) and Mus showings all occur at ornear the contact between analtered pillow basaltunit and over- lyinginterbedded tuff and calcareous siltstone units (Figs. 49 an'3 53). The mafic volcanicrocks appear to form thecore of a major antif,ormof unknown complexity and attitude.

HISTORY

The Windy-Craggy gossan was first noted by J. J. MzDougall of Falcon- bridgeLimited while doing aerial reconnaissance ofthe area. A follow- upground survey in1958 resulted indiscovery of the Windy-Craggy showing. lhe discoveryshowing is essentially a narrowgossan along the southernheadwall of a cirqueglacier. Packsack drillfing in 1960 (1 1 holestotalling 240 metres) by VenturesLtd. (later abscrbed by F,slcon- bridgeLimited) intersected a massivesulphide body beneath the surface gossan. lhree diamond-drillholes totalling 410 metres were completed in 1965(65-1, 2, 3; Fig. 54),and an additional 10 holestotalling 2 250 metres were drilled in 1981.

In 1982 hole 1981-9 was extendedand two new holes (1 1 and 121 were completedfor a total of 1 364 metres of drilling.This work was financed byGeddes Resources Limited through a drillingfund; work on the property was managed by FalconbridgeLimited. By spending $1 500 000 in 1981 and 1982, Geddes WsourcesLimited has now earned a 49 per cent undividedinterest in the Windy-Craggy property.

DEPOSIT GEOLOGY

Surfacegeology and drillhole locations are shown on Figure 54. Drillingto date on the Windy-Craggy propertyhas defined a concordant, tabular,steeply northeast-dipping pyrrhotite-chalcopyrite+pyrite massive sulphide body over 1 000 metres longand averaging approximate1.y 100 metres inthickness. mere are unknown extensionsalong strike an'3 down dip.mpper grades are variable,ranging from less than 'I per centup to

6 161 14 per cent in narrowhigh-grade supergene enriched intersections. The drill-indicated reserves ofthe best grade part of themassive sulphide zone are reported to be over 85 milliontonnes averaging 3.04 percent copper and 0.03 per centcobalt within an overallinferred tonnage for thedeposit of 300 milliontonnes averaging 1.52 per centcopper and 0.08 per cent cobalt(Northern Miner, January 13, 1983).

Figre 54. Geology and drll I hole locations, Wlndy-Craggy dewsit.

162 The most northerlydrill hole, 82-12, intersected a predominantlymassive pyrite zonefrom 24 to 187 metresthat averaged 1.78 Eer centcopper (includes 53 metresaveraging 3.09 per centcopper). Ihe top 12.5metres ofthis intersection also averaged 0.58 percent zinc, '79 grams silver pertonne, and 1.34 grams gold per tonne, and the bott.om 38.7 metres averaged1.75 per centzinc, 16.25 grams silver per tonne, and0.47 grams gold per tonne.Concentrations of zinc, silver, and goldappear to increase towardthe northern end of thedeposit which iis predominantly pyrite.Pyritic sections also tend to be coarser andmore granularin texture andframboidal texture is locally well developed.Massive pyrrhotitesections are generally much finergrained. Stilpnomelane is a common accessorymineral in the massivesulphide zone, which is also locallymagnetite rich. Pyrite and pyrrhotitebands artd laminaealso occur in argillites and cherts of theimmediate hangingwall and footwall ofthe deposit. Small-scale fold structures are common in the bandedand laminatedsulphide zones.

One of the most interestingfeatures of the Windy-Craggy deposit IS the relativelyhigh concentration of cobalt in massivepyrrhotite sections. Drill intersectionsaveraging greater than 0.1 perc'ent cobalt are common;some shortintersections contain greater than 0.2 percent.. Ihe bestcobalt grades do notnecessarily correlate with better copper grades as shown on Figure 56. FalconbridgeLimited research indicates no discreetcobalt mineral is present;cobalt is probably in solidsolution with pyrrhotite and it mightnot beeconomically recoveralle.

In additionIn massiveto sulphide mineralization, a hrge zone with stringers and disseminationsof pyrrhotite and chalcopyriteoccurs in chlorite-epidote-serpentinealtered pillow basalts, cherts,. and argillitesalong both sides ofthe massive sulphide body. The gradeof stringermineralization generally averages 0.5 to 0.8 1-r cent ,copper withsporadic intersections up to 2 per cent. The stringer zonehas relatively low cobalt,silver, andgoldconcentrations. A major northwest-trendingfault zone separates stringer mineralization from relativelyunaltered interbedded calcareous siltstones and andesitic to dacitictuffs and flowssouthwest of the deposit. A similarfault may also be present belowthe glacier on thenortheast side of thedepo:;it as indicated by drillhole 81-10 (Fig. 56).

The mixed calcareoussiltstone-volcanic unit is probatilythe strati- graphichangingwall of thedeposit. Ifaltered mafic Elillowed b,asalts andcherts with stringer sulphide mineralization comprise the strati- graphicfootwall of thedeposit, asthey normally do in theclassic volcanogenicmassive sulphide model (Fig.55). then drillhole data could beinterpreted as shown on Figure 56. In thisstructural model the massivesulphide body is foldedinto tight anticline-syncline pair); that areseparated and displaced by high-anglenormal and reve.rse faults. In this model thebest copper grades are located at the bast! of theumssive sulphide bodyand in theimmediate footwall.

163 Flyre 55. %delfor Cyprus-typevoicanogenlc massive sulphide deposits. bdified after Hutchinson and Searie (1971).

INTERPRETIVE DRILL SECTION - WINDY-CRAGGY DEPOSIT

SW NE

Fipre 56. interpretivedrl ii section,Wind/.Crag(y deposit.

164 r d' z e 2

165 The massivesulphide intersection in drillhole 82-12 is bounded by interbeddedvolcanic rocks and calcareous siltstones but does not appear to come to surface.Perhaps the intersection is nearthe top of a tight anticlinalfold structure. As describedpreviously, zinc concentration increasestoward the 'upper' and 'lower' contacts of the massive sulphide intersectionsuggesting that zinc is enrichedat the top of themassive sulphide body. Thisapparent zonation ofcopper and zincwithin the Windy-Craggy deposit is consistentwith that normally observed in volcanogenicmassive sulphide deposits.

GEIIETIC MODELS

The threestratiform massive sulphide deposit types described in this paperhave one unifying characteristic; they allformed by in situ precipitation ofsulphides onto the seafloor, probably in closeproximity to a hydrothermalvent. lbese vents or fumaroles were probablysituated alongmajor faults that provided escape conduits for heated formational watersand convectively circulating seawater. Differences in themetal contentand mineralogy of the deposits (Table 1) canbest be explained in terms of differenttemperature regimes assuggested by Finlow-Bates (1980). Large (1977), and others (Fig. 58).

Stratiformdeposits of theGataga district formed in a fault-controlled continentalmargin sedimentary basin or troughand typically have low temperaturecharacteristics. ?hat is, theyhave very low coppercontent, highbarite content, and no appreciablefootwall alteration or veining. The lack of coevalvolcanic rocks in the section is consistentwith the inferred low temperatureenvironment of formation. In contrast,the Midway deposits formedboth within platformal carbonates and in overlying transgressiveclastic rocks. Periodic movements alongnearby growth faultsprobably triggered episodes ofcoarse clastic sedimentation that produced the coarsening upward sedimentarycycles. Unlike deposits of the Gataga district, whichgrade outward into thin laminae of nodular barite,distal equivalents of the Midway stratiformmassive sulphide zone are mainly pyriticcherty exhalites that haveonly minor amounts of intercalatedbarite. Mineralization on the Midway property is predominantlymassive, locally recrystallized pyrite. It haslocal high-grade zinc,lead, and silver values but low bariteconcentrations. The Lower zonealso contains copper with some gold, titanium, and bismuth. These featuressuggest the Midway deposits formed atslightly higher temper- tures,and/or closer to hydrothermal vents than deposits of the Gataga district. A majorhigh-angle fault occurs on the west side of Midway deposit;this fault might have beenthe main conduitfor hydrothermal fluids,not only for Midway butalso for the nearby Silvertip silver- lead-zincvein system.

In contrast to the stratiform pyrite sphalerite baritetgalena deposits of theGataga district and the Midway deposit,the cupriferous massive sulphidedeposit at Windy-Craggy is much likethe Cyprus-type volcanogenicmassive sulphide deposits. Cyprus deposits occur in a sequence

1 66 of alteredpillow basalts of ophioliticaffinity (Hutchinson and S?arle, 1971).Typically they have a well-developedunderlying stringer and disseminatedsulphide zone. The massivecupriferous pyrite body is overlain by unalteredvolcanic and pelagic sedimentary rocks (Fig. 55). All these features are present at Windy-Craggy.

TheCyprus depositsoccur atthe contact of thesubcircular ‘Iroodos Igneous Complex which consists of an ultramaficbase, a xjheeted gabbroic dyke swarm, andupper altered pillow basalts. me complex is believedto haveformed at a spreadingrift system within continental crust” The Windy-Craggy depositandother nearby stratiform missive sulphide occurrences of unknown significancealso occur atthe contact of a subcircular mass of mafic volcanicrocks (Fig. 53) and this mass may have anophiolitic core similar tothat of the TroodosIgneous Cnmplex. Therefore a similarenvironment of formationmight apply to the Windy- Craggy area,that is, a spreadingrift systemwithin continental crust, perhaps in a back arcbasin setting similar to that ofthe present day JapaneseIslands or calf of California(Fig. 57). The andesiticto dacitictuffaceous rocks intercalated with sedimentary strata overlying the windy-Craggy deposit may, in fact,represent fallout: from anactive volcanicarc that was located West of thebasin. ‘These ide,3s are speculative and requireadditional regional mapping to substantiate.

HYPOTHETICALEVOLUTION OF THEWINDY - CRAGGYDEPOSIT

SPREADING CENTRE

COMPRESSION

Figure 57. Hypotheticalevolutlon of thewlndyaraggyceposit.

167 pH =4 ZCI = 1 M

PO, = lU" atm

HEMATITE PYRITE BARITE

EXHALATIVE Y DEPOSITS HEMATITE I MAGNETITE I

L I I 100 SO?iH,S 300 T OC AFTERFINLOW-BATES. 1980

pH=5 S=lU'M

MAGNETIT

HEMATITE

PYRRHOTITE

CHALCOPYRITE

100 200 300

1 = GATAGADEPOSITS 2 = MIDWAY 3 =WINDY - CRAGGY

Fiyre 58. Log totalsulphur-temperature and log oxfgen fugacity-temperature dl agraffi and stab1 I ity fields of phases comn to exhaiativedeposits. Hypothetical f lei& of formtion for deposits of the Gataga district and the Midwayand Winq

168 The highcopper and anomalous cobalt content of the Windy-Craggy ore is consistentwith modela of convective downward circulation of seawater andleaching of metals from a maficto ultramafic vo1ca:nic pile in the mannerdescribed by Spooner (1980) forformation of the Cyprus deposits. Although Windy-Craggy hasalmost all thefeatures of thse Cyprusnodel, there is onevery important difference -- size.Ihe Windy-Craggy deposit hasinferred reserves on theorder of 300 milliontonnes, which i:3 much largerthan the largestof the known Cyprus deposits (15 milliontonnes). The discovery of a Cyprus-typedeposit of thissize and grade in this relativelyunexplored area suggests that volcanic-sedimentary rocks of theAlexander terrane have a veryhigh resource ptenti(n1. In v:iew of thedeposit model presented in thispaper, the contact between altered maficvolcanic rocks and overlyingunaltered volcanic-sedimentary rocks wouldbe a primeexploration target. The apparentLate Triassic ageof thehangingwall rocks at Windy-Craggy shouldalso be taken into consider- ation.Ifthe mafic pillowed volcanic rocks are Paleozoicinage as inferred by theregional mapping of Campbelland Dodds (1979), then a majorunconformity or thrust fault may exist betweenthe mafic volcanic rocks and theoverlying volcanic-sedimentary unit. Alt.ernatively, the entire packagemight be Late hiassic in ageand thereforecorrelate with othermafic volcanic units such as theStuhini Groupof the Intermontane Belt and theKarmutsen-Nikolai assemblage of theInsular 'Wlt.

AcKuIniLmGMmTs

The author would like to thank Rob Came and Mike Philips of Archer, CathroHoldings Limited, Brian Ball of Cordilleranhgineering Limited, and Wrry Chandlerand Jim McDougallof FalconbridgeLimited for much valuableinformation and logistical support during visits totheir respectiveproperties. Mike Fournierprovided able andch,eerful assistancein the field.

REFERENCES

Campbell, R. B. andDodds, C. J. (1979): operation Saint Elias,Elritish Columbia, in currentResearch, Pt. A, Geol. Surv., tknada, Paper 79-1A, pp. 17-20. Dawson, K. M. and Orchard, M. J. (1982): RegionalMetallogeny ofthe NorthernCordillera: Biostratigraphy, Correlation, and Metallogenic Significance Beddedof Barite Ozcurrencesin Ea!;tern Yukon and Western District Mackenzie,of in CurrentResearch, Pt. C, Geol. Surv., Canada, Paper 82-1C, pp. 31-38. Finlow-Bates, T. (1980): TheChemical and PhysicalCbntrols Dn the Genesis of SubmarineExhalative Orebodies and their Implications for FormulatingExploration Concepts -- A Review, Gecd. Jb., Vol. 40, pp. 131-168.

169 Gabrielse, H. (1969) : Geology of theJennings River Map-Area, British Columbia, Geol. Surv., Canada, Paper 68-55, 37 pp. Gordey, S. P. (1982):Devono-Mississippian ('Black Clastic') Sedimen- tation andTectonism in theNorthern Cordillera, in Program andAbstracts, Geol. dssoc. Can., CordilleranSection, Meeting, Vancouver, B.C., February1982. Gordey, S. P., Abbott, J. G., and Orchard, M. J. (1982) : Devono- Mississippian(Earn Group) and Younger Strata in East-Central Yukon, in CurrentResearch, Geol. Surv., Canada, Paper 82-1B, pp.93-100. Hutchinson, R. W. andSearle, D. L. (1971):Stratabound Pyrite Deposits in Cyprusand Relations toOther Sulphide Ores, SOC. Min. Geol., Japan, SpecialIssue No. 3,pp. 198-205. Large, R. R. (1977):Chemical Evolution and Zonation of Massive Sulphide Deposits in VolcanicTerrains, Econ. Geol., Vol. 72, pp.549-572. MacIntyre, D. G. (1980a):Driftpile Creek-AkieRiver Project, B.C. Ministry of Energy,Mines & Pet. Res, GeologicalFieldwork, 1979, Paper 1980-1, pp. 55-67...... (1980b) : CirqueBarite-Zinc-Lead-Silver Deposit, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1979,Paper 1980-1, pp. 69-74...... (1981a): Akie RiverProject, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1980. Paper 1981-1, pp. 32-41...... (1981b):Geology of the Akie RiverBarite-Lead-Zinc Mineral District, B.C. Ministry of Energy,Mines & Pet. Res., Prelim. Map 44...... (1982a) : Akie River Project, B.C. Ministry of Energy, Mines & Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp. 142-148...... (1 982133 : Geologic Setting of Recently Discovered Stratiform Barite-SulphideDeposits in Northeast mitish Columbia, C.I.M., Bull., Vol.75, NO. 840,pp. 99-113...... (1982~): Midway Occurrence, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp.162-166. MacIntyre, D. G. andDiakow, L. (1982): Kwadacha Barite Deposit, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1981,Paper 1982-1, pp. 149-155. Morganti, J. M. (1981): Sedimentary-TypeStratiform Ore Deposits: Some Modelsand a New Classification, Geoscience Can., Vol. 8, No. 2,pp, 65-75. Spooner, E.T.C. (1980) : Copper-PyriteMineralization and Seawater Con- vection in Oceanic Crust -- The Ophiolitic Ore Deposits of Cyprus in The ContinentalCrust and Its MineralDeposits, D. W. Strangway, editor, Geol. Assoc. Can., SpecialPaper 20,pp. 685-703. Stollery, J. W. andSellmer, W. H. (1982) : Midway, An Analysis of a New Massive SulphideDiscovery, Cdn.Min. Jour., Vo1. 103, No. 4, pp.68-71.

170 INTRODUCTION

The Brucejack Lake (Sulphurets, MI lO4B-118) preciousm!tals epithermal prospect,located approximately 65 kilometresnorthwest of Stewart, was examinedfrom August 3rd to 6th inclusive. Brucejack Iake, part of the largerSulphurets property, is covered by the Red 1 Group mineral claims (RedRiver, Red River 2 to 7 inclusive, and Tedray 12). In total,the Sulphurets propertyconsists of 240 units includingthree fractional claimsand six two-post claims. It coversparts of 104B,/8E, 8W. 9E, and 9W. me claims areheld by GranducMines Limited, Esso ResourcesCanada Limited,and Sidney F. Ross. The property is beingoperated ly Esso ResourcesCanada Limited under option from Granduc Mines Limitedand Sidney F. Ross. Access is by helicopter from Stewart.During exploration, Esso ResourcesCanada Limited utilized a helicopterfrom thei.r base camp located on thenorth side of MitchellCreek, about 200 metreseast of McTagg Creek.

GEOLOGY MID IIIUERALIZATION

Smallprecious base metal showingsoccur over a largearea within altered EarlyJurassic andesitic volcanic and sedimentaryrocks (arenite and argillites) of the Unuk RiverFormation. The mineralizationoccurs in sericiteschists that represent areas of moderate to intense wallrock alteration.Hornblende syenites and alltalifeldspar syenites that intrudethesequence have also undergone local intense alteration. Numerous north-south to northwesterlyfaults cut acrossthe property -- includingthe Brucejack fault. Middle Jurassic Betty Creek Formation rocksoccur to the east. The dominantalteration products include sericite, K-feldspar. silica, carbonate, and chlorite.Sulphide mineralization, found in fiveseparate mineralized zones spaced along a 7- kilometrebelt, occurs as low-gradedisseminations ('porphyry' gol.d), as veins(for example, Iron Cap), and as epithermal stockworks (for example, BrucejackLake) . Mineralsinclude pyrite, chalcopyrite, molybdenite, ruby silver, stephanite,cerargyrite, electrum, native gold, tetrahedrite,freibergite, argentite, galena, sphalerite, a!nd bornite in a gangue of quartz,barite, and calcite.Cerargyrite has been identified in a purplerind on silver-bearingveins in the Brucejack area. (Dane Bridge,personal communication, 1982).

The main area of interest this year was Brucejack Lake where:several showings of precious metal mineralization havebeen found and partially testedover a 2-square-kilometrearea. At the time of thewriter's visit, 120 short,hand-blasted trenches hadbeen completed and $diamond drilling was inprogress.

171 172 During 1982,53 diamond-drill holes totalling 4 633.4 metres were drilled onthe Sulphurets property. On the Brucejack Lake prospect 1981 and 1982 drillingincludes diamond-drill holes 28, 29,32, 40 to 44 and63 to 76 inthe Peninsula zone; 54 to 62 and 80 to 91 in the Westzone; 33 to 36 in theStockwork zone; 52, 53 and 92 to 95 in theGalena showing; 45 to 48 in the 5.9 vein; and 17, 30 and 31 in theDiscovery area o,n the peninsula.

Two principalzones havebeen identified:

(1) PENINSULA ZONE (NearShore zone), which has been traced far 265 metres and to a depth of 140 metres by intersections in 22 drill holes. The zone is still open.Grab samples cctllected bsy the writer ranged in value from 0.1 ppn gold and43 ppn silver up to 2 ppn gold and 2 924 ppn silverwith lead andzinc values up to 1.49 per cent and 3.33 per centrespectively.

(2) WEST ZONE, which was tested by 21 drillholes along a length of 310 metres and to a depthof 60 metres. It is still open.True widths areestimated torange from 0.6 to 4.0 metres. Some veryhigh gradesovernarrow widths havebeen obtained. Ruby silver, freibergite, electrum, nativegold, stephanite, galena, pyrite, and sphaleriteoccur in a stockworkofquartz veinlets in sericitic andesitictuff. Mineralized grab samples containing sulphides in quartzveinlets that the writer collected ranged in valuefrom 4.8 ppn gold and severalthousand ppn silver up to 2;’5ppn goldand 67525 ppn silver. Copper rangedfrom 0.54 per cent up to 2.74 per cent,lead from 0.4 per cent up to 2.50 per cent,. and zinc from 0.027 percent up to 4.5 per cent.

Othershowings or zones tested include (see Fig.59):

(3) GALENA SHWING -- galena, sphalerite,pyrite, chalcopyrite, and nativegold occur in quartz and bariteveinlets in sericite schist (alteredandesitic tuff); grab samples collected by the writer ranged in value from 1 ppn goldand 69 ppn silver to 9.3 ppn gold and 1 276 ppn silver;copper values ranged from0.02 to 0.!52 per cent,lead from 0.04 to 7.7 percent, and zinc from 0.02 to 4.78 per cent.

(4) TRENCH 108-111 RIDGE -- galena,tetrahedrite, electrum, argentite, sphalerite,pyrite, and chalcopyriteoccur in a quartzstockwork in sericiteschist (altered andesitic tuff); grab samp:.es collected by the writer rangedin value from 0.3 ppn goldand 10 ppn silver to 56 ppn goldand 5 166 ppn silver;copper values ranged from0.05 to 0.68per cent, lead from 0.6 to 5.9 percent, and zinc from 0.12 to 5.87 per cent.

(5) 0.5 VEIN -- sulphides in quartz veins in serici.te schist;:grab samplescollected by the writer ranged in value from 16.5 pp gold and187 ppn silverto 36ppn gold and 235 ppn silver; copperranged

173 from 0.25 to 0.66 percent, lead from 1.19 to 3.8 percent, and zinc from 3.01 to 4.5 per cent.

(61 STOCKWORK ZONE -- pyrite,galena, and Sphaleritein a quartzstockwork in sericiteschist.

(7) 5.9 VEIN -- nativegold, electrum, pyrite, galena, sphalerite, ruby silverin a quartzstockwork in sericiteschist.

The writer muldlike to acknowledgethe cooperation and logistical supportprovided by ESSO ResourcesCanada Limited.

174 MOUNT JOHNNY PROSPECT (104B/11E)

By T. G. Schroeter

INTRODUCTION

On Wgust5th the writer made a brief visit to Skyline wloration lAtd.'s Mount Johnny (Reg claims, MI 104B-77) massivesulphide prcperty, whj.ch is locatedapproximately 120 kilometres northwest of Stewart onthe west flankof Mount Johnny (see Fig. 60). Access to theproperty, which consists 172of units, is viahelicopter from eiti-.er Stewart or Eddontenajon.

FIgJre 60. Location map, Mount Johnny prospect.

175 GEOLOGY AUD III~IZATION

The base of bunt Johnny is underlain by intercalatedphyllitic grits, siltstone, andan andesitic-rhyoliticsequence ofEarly Jurassic age (Unuk RiverFormation ?). The volcanicsequence locally shows persistent autometamorphictextures. A sequencelowerof Middle Jurassicrocks (BettyCreek Formation ?) overliesthe Early Jurassic rocks but are devoid of significant mineralization.

Copper-goldmassive sulphide mineralization has been located in three zones:Pick Axe, Cloutier, and McFadden (see Fig. 61). The Pick Axe andCloutier zones are localized in a sequence of rhyolitictuffaceous rocks.Mineralization consists of nearmassive chalcopyrite and pyrite in c rtztcarbonategangue.

Figure 61. bunt Johnny prospect (Inset on Fig. 60) (based on covany Plans).

176 (1 ) Pick Axe Zone

Reportedlytraced more than 1 000 metres,the zone has beencon- firmed by drillingalong a length of 15 metres(George Cross wws Letter, May 14, 1982). Assay results fromgrab samp1,es collected by thewriter are as follows:

Saw I e Br I et No. Descrlptlon Gold SI lver CopperLead Zinc ppm ppnper cent per cent per cent

JM-82-2 Mass Ive 0.018 0.,04 2 3.93 124 chalcopyrltepyrite

JM-82-3 ChalcopKltkpyrlte 2 90 3.57 0,.02 0.078 In quartz

JM-82-5 Chalcopyritepyrlte 2.3 4.32111

JM-82-6 Chalccpyritepyrlte 0.7 255 3.42 <0.02 0.012 In 'rhyolite'

JM-82-8 bar masslve pyrite 1 100 2.63 0.045 0.090 and chalcopyrite

(2) Cloutier Zone

Apparentlytraced along a lengthof 490 metres(GeDrge Cross hews Letter, May 14, 1982). Assay results€or grab samp1.e~ collected by thewriter are as follows:

Saw le &let No. Oescrlptlon Gold SI lverLead Copper Zlnc Pppm pm percent per cent per cent

BJ-82-9 Chalcopyrite-pyrite 1.7 19 1.37 0.03 0.,03 In sillclfled tutt

BJ-82-11 Pyrite In slllcltled

8J-82-13 bar massive 2.3 19 2.1 <0.02 0..022 chalcopyrltepyrlte

8J-82-14 Chalcopyrite-pyrite

BJ-82-15 bar masste-pyri Ive 3.4 140 6.50 co.02 0.045 chalcopyrite

8J-82-16 bsslve pyrite- 0.3 65 5.12 <0.02 0.017 chalcopyrite

E.!-82-I7 Chalcopyrltepyrlte 0.3 45 4.15 c0.02 0.012 in quartz

177 At the time of the writer's visit,drilling was inprogress on diamond-drillhole 10. Diamond-drillhole 9 intersected a massive sulphidesection from 35.8 to 38 metres.

(3) McFadden Zone

High-grademassive pyrite boulders were found in anarea 245 metres by 45 metres(George Cross News Letter, May 14,1982) that is locatedapproximately 1 kilometresoutheast of theCloutier zone.

Diamond drilling exceeded 750 metres in eightholes, and geophysical surveys were carriedout throughout the summer and fall. In mid- September,Placer Developnent Limited optioned the property from Skyline ExplorationsLtd.

178 KUTCHO (IREEK PROPERTY (1041/1)

By T. G. Schrater

INTRODUCTION

The part of theKutcho Creek massive sulphide deposit (MI 104/1-60) owned by Sumac Mines Ltd. was visited on August30th. It is locatedapproximately 100 kilometres east of Ease Lake. During1982, Sumac Mines Ltd. constructed a 12-kilometretote road from theKutcho airstrip t.o the property. The company thenflew surface and underground equipment to Kutcho airstrip and moved it to theproperty.

Sumac MinesLtd. completed a 218-metre crosscutinto the ore zone for bulksampling purposes and collected 145 tonnes of ore (see Fig.62). They alsoconducted 1 525 metres of surface diamond drilling.This bringsthe total number of holesdrilled by Sumac Mines Ltd. to 128 for approximately 21 335 metres in total. ESSO Minerals Canada, ownBrs of part of themssive sulphide mineralization, has also drilled 9 200 metres. Consequently,total drilling on the KutchoCreek property exceeds more than 30 535 metres.

Fi yre 62 Sketch oi Sumac Mines Ltd. '5 KutchoCreek property.

179 i

180 Estimatedreserves for the Sumac Mines Ltd.property are approximate.ly 11 milliontonnes grading 1.68 per cent copper, 2.14 per centzinc, 25.23 grams silver per tonne, and 0.26 grams gold per tonne.

GEOLOGY AND IIIUERALIZATIOU

Thegeology of the crosscut is shown on figure 63. Twc, main zones of massivesulphide ore mineralizationconsisting of chalcopyrite,pyrite, bornite,sphalerite, and minorgalena and tetrahedrite were intersected in the crosscut. The first, A zone, is 4 metres wide, theseca'nd, R zone, is 13 metres.

In addition, a C zone was intersected below B zoneand consists of greaterthan 80 metres of massivefine-grained pyrite (see Fig,. 63). Metal zoningwith a zinc-richhangingwall appears toexist. The ore zonesdip 45 degrees to thenorth and crosscut theenclos.ing rocks which have an averagedip of 70 degrees to the north.

AcKNmlXlamTs

The writer acknowledgesthe hospitality of Taiji &no, Roy Suzuki, ,and Ed Holt of Sumac Mines Ltd.while visiting the property.

181 MAJORMINERAL DEPOSITS

1. SCOTTIEGOLD MINE 2. DAG0HILL DEPOSIT 3. BIGMISSOURI MINE

4. CONSOLIDATEDSILVER BUTTE DEPOSIT

5. INDIANMINE 6. SEBAKWE MINE 7. E.C. SILVERMINE

8. SILEAKPREMIER MINE 9. RIVERSIDEMINE 10. DUNWELLMINE

11. SILVERADOMINE

12. PROSPERITYAND PORTER IDAHO MINES

Figure 64. Regional geoloy and mineraldeposits.

182 SWON RIVER PROJECT, STFXART, BRITISHCOLUPLB:tA 104B/1)

By D. J. Alldrick

INTRODUCTION

InJuly, 1982 the Ministryinitiated a study of the geologicalsetting of precious metal deposits in the Salmon RiverValley which trends north fromStewart for 35 kilometres. The specificobjectives are:

Document structuraland stratigraphic relationships of the host. rock volcanicsequence and its contactrelationships with adjacent terranes.

Determinethe evolution and depositional environment of thevolcanic system from petrographic and geochemicalstudies of the sequenc!e.

Analysethe structural, stratigraphic,mineralogical, and trace elementcharacteristics of theprecious metal andbase metal deposits of the area.

Conductmetallogenic studies and define areas of: high mineral potential.

Sample for fossil andradiometric dating of thehost rocks and ore zonesand compare them withother volcanic terranes aroundthe Middle Jurassic Bowser basin.

HISTORY AUO PREVIOUS WORK

Prospectorsbegan to explore the Stewartarea in 1898 enroute to the Klondike. No major placer gold deposits were foundbut mineralized float led to thediscovery of gold-quartzvein deposits. Continued prospecting locatedthe gossan at SilbakPremier mine in 1910,Subsequently, the Stewart camp became thethird greatest lode gold proc3ucing ar’aa in British Columbia. Between 1918and 1968 theSilbak Premier mine production alone totalled 4.3 milliontomes grading 13 grams gold per tonne and 298grams silver per tonne.Tipper and Richards (1976) outlined the tectonic evolution ofthe region. Major reports by Gsove (1971)and Galley(1981) include historical reviews of geologicalstudies in the area andextensive bibliographies. Barr (1980)provides a concise geologicalreview of the SilbakPremier mining camp.

Explorationin the Stewart area duringthe past few yearshas been intensive. Companies are reassessing several known propertie:s and testinginteresting new prospects; for example, theProsperity/I’orter Idahosilver deposits; the Silbak Premier, Indianand Big Missouri mines;

183 REGIONAL VOLCANIC VOLCANIC SEQUENCE SEQUENCE ONTHE BIG MISSOURI PROPERTY

...... -.-. -. - . -...... - ......

Pr0"i"Ce iE & W) zones Consolidated Silver Butte 1 b

=:=.-..--dc.-,=

b ...... -. -. -. -. a

......

.?. ..

EPicIasfics along Bear River Ridee

61a 61b

~ ~~~

Figure 65. Schemtlcstratigraphic column.

184 theConsolidated Silver Butte MinesLtd. deposit; and many scattered depositsin the BigMissouri claim group. There is also anongoing exqlorationprogram around the producingScottie Gold mine.

REGIOMAL GBOMGY

The north-northwest-trendingbelt of volcanic rocks (shaded on Fig. 64) throughthe central part of the projectarea is the focus of thisstudy. It is bounded by a thicksedimentary sequence trending north-northwest alongthe eastern edge of the map-areaand is cutoff by a series of intrusiverocks to the west (Tipper and Richards, 1976).

All themajor ore deposits andalmost all the smaller mineraldeposits of the area occurwithin the volcanic sequence. Hanson (1935) andGrove (1971) identifiedthis sequence as 'Hazelton Group'and 'Hazelton Assemblage'respectively. They assumed that all thevolcanic terranes of

LEGEND (ALSO FOR FIGURES 66 AND 67)

SEDIMENTARYSEQUENCE

Ba CONGLOMERATICBLACK SILTSTONES AND Bc BLACKTOGREY SILTSTONES SH ALE S Ed BLACK SILTSTONES AND PYRITIC SHALESPYRITIC ANDSILTSTONES BLACK Ed SHALES BbFOSSILIFEROUS LIMESTONE

VOLCANICSEQUENCE

7 BLACKSILTSTONE FELSICVOLCANIC ROCKS (CONTINUEDI 3 GRADEDGREY TUFF lCONTlNUEDI INTERMEDIATEVOLCANIC ROCKS 3c WITHTUFF. LENSES OF 3d BLA C K TUFF 6.3 BLACK TUFF 36 MAROON 6b BLACKLAPILLI TUFF, BLEACHED FRAG- Za RHYOLITEASH FLOWTUFIz, HIGHLY PYRITIC, ME NT S LIMESTONE BOULDERS, SCORIA FRAGMENTS SCORIA BOULDERS, LIMESTONE MENTS 5a GREENTUFF BRECCIA 2b RHYOLITEASH FLOW 'TUFF, MINOR OR 5b GREENTUFFS, LAPILLI TUFFS, AND FLOWS TRACEPYRITE, FRAGME'NTS OF le AN0 5c PURPLE TUFF SCORIA 5d CHERT-CARBONATE LENSES, iSULPHlDES la BLACKTUFF, FINE TO MEDIUM GRAINED 4 PURPLE ANDMAROON TUFFBRECCIA. lb FOSSILIFEROUSLIMESTONE LAPILLITUFF, TUFF, AND EPlCLASTlC ROCK IC PALEGREEN TUFF FELSICVOLCANIC ROCKS Id GREY-GREENTUFF 3 GRADEDGREY TUFF: le BLACKCARBONACEOUS LAPILLI TIJFF, 3a TUFFBRECCIA ABUNDANTPUMICE FRAGMENTS, LOCAL lb 3bLAPILLI TUFF NODULES,LOCAL PYRITE

SYMBOLS

LITHOLOGICCONTACT ...... -._. -.. FAULT ...... -.A-

LITHOFACIESCONTACT THRUSTFAULT ...... 3/

185 theregion arecontemporaneous with those of the typeHazelton area 200 kilometres to the southeast. Since fault and intrusivecontacts border thevolcanic sequence in theStewart area, the correlation is tenuous. A richlyfossiliferous limestone unit and fossiliferouslimestone nodules occur in darktuffaceous rocks of thesequence and may provide a defin- itiveage for this metal-rich volcanic belt.

Throughoutthe area mapped thisseason, the sedimentary rocks were thrust westwardover the volcanicrocks. The sedimentarysequence consists of black and greysiltstones and shales with basalconglomeratic horizons. A thinfossiliferous limestone crops out near the base of thesequence. Fossilage determinations completed in themid-1960's (Grove, 1971) defined a broadMesozoic age range. Grove assumed a Middle Jurassicage andidentified these rocks as 'Bowser Assemblage.'Subsequently, Tipper andRichards (1976) described similar sedimentary sequences from the upperHazelton Group. Consequently the exactage and correlation of this sedimentarysequence remains uncertain and thefossil horizon has been resampledfor further macroand microfossilstudy.

A complex series of intrusiverocks along the western edgeof the map- areadefine the eastern margin of theCoast Plutonic Complex.Based on limited K/Ar age dating by the United StatesGeological Survey, the variousbatholiths and smallerstocks range in agefrom Middle Jurassic to MiddleEocene (Grove, 1971). ?he compositions range from granodiorite todiorite. A wide variety of dykerocks occur throughout the belt -- compositionsrange from aplite togabbro. In some areasthe intrusive rocksare spatially related to ore deposits, for example, at theScottie Goldand Silbak Premier mines.

VOKANIC STRATIGRAPHY

Volcanicunits within the map-area (Fig.66) strike north tonorth- northwestand generally dip to the west. E'ragmentsof subjacentlith- ologies in tuff breccia,and grading in thethick ash flow of unit 3, suggestthat stratigraphic tops are to the west. Galley(1981) identi- fiedgraded beds in epiclasticrocks of unit 4 which also show that stratigraphictops are to the west.

The overallthickness ofthe volcanic sequence mst exceed 700 metres (Fig. 65) buttotal thickness cannot be estimated on thebasis of this season's work. The siltstones of unit 7 may mark thetop of the sequence. The lower part ofthe stratigraphic section has not been studied in detailbut includes a thick section of tuffs,airfall tuffs, andepiclastic rocks (Fig. 65b). lhese are exposed along the Bear River Ridgesouth of Mount ShortyStevenson.

Galley(1981) developed a detailedtype section ofthe stratigraphy on the Big Missouriproperty. Thefew modificationsto Galley's work are based on excellentrock exposures along the west slope ofMount Dillworth beyond his map-area. Selectedfeatures of thestratigraphic sequence (Fig.65) are described following.

186 A fossiliferouslimestone band (lb) is interbedded with tuffs of unit la on thenorthwes't edge of the Mount Dillworthsnowfield. Nearby, large nodules of the same fossiliferouslimestone, up to 0.5 me'xe across,are envelopedinblack carbonaceous hff(unit le). Textures suggest that thenodules were unlithifiedcarbonate rmd balls when incorporatedinto thetuff. The same carbonaceoustuff typically contains angular white pumicefragments and locally hosts blebs of pyrite up to 3 centimetres in diameter. Dykes (personalcomnunication) traced unit le ?IS farsouth as Fetter Lake beside Dag0 Hill. Thishorizon either underlies unit 2 directly or is separatedfrom it by a thinlayer of unit la tuff.

Variouswrkers identified the rocks of unit 2 asrhyolite, chert, or exhalite, !xt theexact conposition and originhas not been determined. Resistantrhyolite ash flow tuffs (facies 2a) weather to bright rusty red,nochlar outcrops that form a continuousridge along the western edge of Mount Dillworth. They extend from theRoy Plats to the Unicorn No. 3 workingssouth of Mount Dillworth where a gradualdecrease in thedensity offragments and inthe pyrite content marks thechange to facies 2b, which is exposeddiscontinuously as far south as Fetter Iake. One thin exposureof facies 2b OCCUKS on thewest side of Slate huntain,, and anotherexposure of this unit canbe traced from southeast of Long Lake tothe west slope of Mount ShortyStevenson; southward it gradually changesto facies 2a. Facies 2a carries up to 20 percent disseminated veryfine-grained pyrite in a translucentgrey siliceous matrix. Locally thepyrite occurs asmassive blebs up to 20 centimetreslong. One stratiformpyrite seam on Mount Dillworth is 8 centimetresthick and 6 metres long. This tuff contains numerousrounded carbonate boulders that arerecrystallized (?) to coarse-grainedcalcite; loca.lly there are abundant,large angular fragments of blackscoria.

Unit 3 consists principally of grey tuff. lhe altered maroon facies(3d) is significant because it develops by progressive alteration of the green-greyfine-grained tuff of facies 3c. Oxidation may result from eithersubaerial exposure OK passageof oxygenating fluids through the tuff.

With theexception of themnwell and Riversidemines, 2.11 themineral deposits on Figure 64 arehosted within medium greenandesitic volcanic rocks of unit 5. The rocksare crystal tuffs, 1apil.ti hffs, tuff breccias, andflows. They arecharacterized by plagioclaseand, less commonly, hornblendecrystals and crystalfragments. The basaltuff brecciacontains fragments up to 1.5 metres in diameter andone intact hexagonalfragment of columnar andesite, 1.2 metresacross,, is exposed on Mount Dillworth.Galley mapped a thin,trough-like lens of pillowed andesites on the BigMissouri property. Intermittent exposures and rapid lateralfacies changes in the tuffs preventcorrelation of individual strataalong strike. Perhaps the purple tuff facies in thissequence will providetime-stratigraphic markers of local and posisiblyregional significance to mappingand explorationprograms.

187 y1 r t

188 Intermittentlymineralized lenses of chert, chert-carbonate,and limestone(unit 5d) conpriseore host rocks along Big MissouriRidge. Theserocks and their precious metal mineralization were the €ocus of Galley'spetrographic and geochemical research and his results are summarizedhere. There are many ofthese lenses on t'he Big Missouri property hut only fewa aremineralized. The chert-carbonatezones can occuras individual lenses or as a series of two orthret? stacked lenses lying 2 to 20 metresapart. me individuallenses vary up to 7 metres in thicknessand have been traced over a maximum strikelength of 1.8 kilometres.Typically, they containangular andesite fragment.5: near their lowercontacts; lenses lower in thesequence carry akundant finely disseminatedcarbon. The chert-carbonatelenses may gradeinto massive chert or massivecarbonate zones along strike.

The contactbetween units 5 and 6 is gradational. The medium greenfine- grainedandesites of unit 5 graduallydarken and give way tothe black tuff of unit 6. Rock texturesremain the same in both units and the gradationalcontact undulates through large outcrop exposures. The orientation of contactsbetween units 5 and 6 and also between units 6 and 7 areuncertain (Fig. 67).

Greenschistfacies metamorphism affectedthe volcanic sequence thrmghout the map-area.However, there is no macroscopicevidewe of ext2nsive thermalmetamorphism adjacent to major intrusive bodies. - WEST EAST

MOUNT DILLVVORTH

"49"

GRANDVC

SALMON

METRES

FIgure 67. Geological crosssectton on the west side of bunt Dl I Irarth.

189 On a regional scale thevolcanic sequence forms a west-dippinghomocline averaging 50 degreesdip. Beds steepen to vertical and are locally overturnedadjacent tothe thrust fault contact (Fig. 67), butdips flatten on muntShorty Stevenson. Grove (1971) interpreted a major north-northwest-trendinganticlinal axis east of Bear RiverRidge. On property scale, gentlesecondary warping has a 60-degreetrend at Big Missouri(Galley, 1981) .

Faultingwithin this terrane is common on bothregional and local scales. Regionalnorth-striking features formmajor topographic lineaments. One ofthese, the Long Lake fault,has strata down-dropped on the east side. Directionof movement along many of thefaults has not been determined, but two northeast-trendingfault zones have left lateral displacementand onemajor northwest-trendingfault has relative right lateral movement.

Small-scalefaulting is abundantthroughout the area and creates diffi- cultiesboth in correlating mineralized chert-limestone horizons and in estimatingdilution factors for ore reserve calculations.

HINERALIZATIOU

Mineraldeposits of the Salmon RiverValley are categorizedaccording to theirstructural settings as follows:

(1) Stratabounddeposits (?mineralized wallrock veins) (a) Stratabounddisseminated sulphide deposits: Big Missourimine, Dag0 Hill prospect,Province East zone, ConsolidatedSilver Butte MinesLtd. prospect (?) (b) Strataboundmassive sulphide deposits: Creekzone, Martha Ellen zone, Province West zone, TBI-3 zone, Premier NO. 3 zone,Silbak Premier mine (?)

(2) Massivesulphide vein deposits in major shear zones: Scottie Goldmine, Prosperity/Porter Idaho/Silverado mines, Indian mine

(3) Quartz/brecciafissure vein deposits: OutlandSilver Bar, Lakeview,Spider, Unicorn No. 3, Silver Tip

There is insufficientdata available to classify the importantSilbak Premier mineand ConsolidatedSilver Butte MinesLtd. prospect withany certainty.Galley (1981) provides detailed descriptions and illustra- tions of selectedexamples of type la, lb, and 3 deposits.

Theabundance and specific mineralogyof sulphides distinguish the two categories of stratabounddeposits. However, bothcan occur in the same area, as at the Dag0 Hill prospect. The disseminatedtypes typically carryhigher grades ofgold and silver in pyrite, minor amounts of associatedgalena and sphalerite, and negligible chalcopyrite. The

190 massivesulphide types have typicalpolymetallic volcanogenic massive sulphidemetal concentrations, that is, theyhave ore grade copper, lead andzinc sulphides with accessory hlt recoverableprecious metals. Both styles of mineralizationoccur in chert-carbonatelenses (unit M); the massivesulphide types contain angular andesite fragmen'x and underlie thecherty material. In contrast, in theCalcite CUts showingnear Dag0 Hill, disseminatedsulphides are distributed through the k.angingwal:l side ofthe chert but thelower half of the chert-carbonate lens is virtually barren.

Wallrockveins cut footwall strata or cut both hangingwall and footwall rocks in anarea of stacked lenses. Disseminated coarse-grained pyrite, galena,sphalerite, and highprecious metal values occur in blua-grey quartz-carbonateveins. If the vein density is highenough, the wa:llrock zone may constituteore.

MASSIVE SULPHIDE VEIP DEPOSITS IN WOR SH- ZONES

Thesedeposits have few featuresin common, but all art?hosted within major fault/shearsystems cutting through medium greenandesite.

At Scottie Gold mine, ore-bearingveins are distributed al.ong a conljugate shearsystem developed within and on thenorthern wall of a major:southeast-trendingfault. The high-gradegold mineralizati'sn occurs in a massivepyrrhotite zoneup to 5 metreswide. This zone is symmetr-ically bordered by swarms ofquartz-carbonate-pyrrhotite-base metal su'tphide veinswhich envelope wallrock fragments thathave been intensely hematized,silicified, and carbonatized(Williams, persmal commlnica- tion). Boththe massive pyrrhotite core vein and the bordering vein swarms beargold -- entirestopes with up to 60 grams gold pertonne have beenproduced from thisstructure. Averageproduction grades to September,1982 have been 17.5 grams gold per tonne. Overall gold/silver ratiosare about 2 to 1.

Access to the mine workings is from anadit developed in thesteep hill- sideoverlooking ammit Lake,and exploration work hasoutlined additionalore grade material both above and below thepresent rnining levels. To thesoutheast, the mineralization and theshear ,system featherout; to the northwest, towardthe ammit Lake dioritestock, the shear and veincontinue kt preciousmetal values drop and basemetal grades of thevein increase.

High-gradesilver deposits of the Prosperity/PorterIdaho mine are 4 kilometressoutheast of Stewart.Mineralization is 1ocalj.zed in a :series ofat least six parallel shear zones. '%e shearzones trend 165 degrees, dip 60 degreeswestward, and are roughly 175 metres apart. lb the:south, theshears terminate at, or are displaced by, a majornorth-dipping east- westfault zone. lb the north, the shears arebelieved to continue under thepermanent snowcap of munt Raineyfor more than 2.5 kilometresto the Silverado mine workings where sporadic mineralization is hosted by

191 parallelshear zones of identicalorientation. Mineralization pinches andswells with thewidth of a shearzone, resulting in well-mineralized zonesthat are up to 11 metres wide, 250 metres long,and extend to at least 175metres depth whereold mineworkings end, still in mineralization. The zones are complex, consisting of one or typically two centralmassive sulphide bands each about 60 centimetres wide but locallyconverging and swelling to 2 metres in width.This massive sulphidecore is composed ofargentiferous galena and lesser sphalerite; it provided 29 000 tonnes of directshipping ore with anaverage grade of 2 500grams silverper tonne (Grove, 1971). The wallrockadjacent to the massivesulphide veins carries an average grade of 686 grams silverper tonneover typical widths of5 to 6 metres on bothsides of thevein. Thesemineralized borders consist of intenselysheared country rock that is alteredtoquartz, buff carbonate, abundant manganese oxide, and sulphides. Qrly mrkers reported a mineralsuite consisting ofgalena, sphalerite,native silver, ruby silver,freibergite, andminor amounts of pyrite,chalcopyrite, and argentite. Gold is conspicuous by its absence in this deposit -- typicalassays are 0.17grams gold per tonne.

At theIndian mine, mineralization is localized in part of a major, vertical,155-degree-trending shear and fault zone.Mineralization exposed in the dumps, trenches, and oldmrkings consists of massive, fine coarse-grainedto galena with minoramounts of pyrite and sphalerite.Quartz with minoramounts of carbonate and chloriteare gangueminerals. The sulphides are bandedand brecciated -- features that are attributed to post-mineralization movement alongthe fault zone. Major slickensidesurfaces are exposed at the Galena Cuts zonewhere massivesulphide mineralization is 3 metres wide. Themine produced 13 000 tonnesof ore grading 120grams silverper tonne, 3 grams goldper tonne, 4.4 per cent lead, and 5.5 per centzinc (Grove, 1971). &so Minerals Canada tracedthe fault structure for more than 1 200 metres north of the mine workings (McGuigan, personalcommunication).

QUART?i/BRECCIA FISSURE VEIN DmOSITS

Deposits of thistype are abundant in the Salmon RiverValley but have low tonnagepotential andconsequently are of lesser economic importance. The veinscut volcanic, sedimentary, and intrusive rocks, thus they represent a verylate-stage mineralizing event.

The veinsconsist primarily of quartzbut carry angular wallrock frag- mentsplus scattered coarse crystals and fine-grainedblebs and pods of sulphideminerals. Wallrock fragments within the veins are commonly silicified,but vein walls are sharp with little or no silicification of the wallrock.the Drusy vugs are common. Sulphide mineralsoccur as euhedralcrystals and ascrystal aggregates of pyrite,sphalerite, galena,chalcopyrite, chalcocite, and freibergite;there is minor associatednative silver. Ihe sulphidesare typically concentrated near thecentre of the quartzvein and sulphidecrystals may beup to 3

192 centimetresacross. lhese vein deposits were extensivelyprospected and locally mined fortheir silver content. Galley (1981) reports gold valuesinthe sulphides where fissureveins intersect a stratabound, sulphide-bearingchert-limestone horizon, andGrove (1 9’71) noted free gold in theSilver Tip workings.

EXPIDRATIOU

All themineral discoveries in theregion can be attribut,%d to intensive prospecting. The recentdiscovery ofa preciousmetal deposit by 5so ‘Minerals Canada on theConsolidated Silver Butte MinesLtd. property (NorthernMiner, November 4, 1982)resulted from an aggressivetrenching program. ate showingarea has widespread, pervasive sericitic alteration withzones of abundantbarren pyrite mineralization which hadbeen trenched andsampled by previousworkers.

The generalsequence ofexploration programs in the regioncan be summarized asfollows:

(1 ) Regionalreconnaissance mapping tolocate bleached and altered andesiticvolcanic rocks, chert-carbonate zones, sulphide or mineralizationin veins or fractures.

(2) Detailedfollow-up mappingand prospecting.

(3) Intensivetrenching and sampling.

(4) Tightlyspaced diamond-drill holes.

Geophysicaltest surveys have been completed over stratabound mineralized zoneswith moderately encouraging results (Dykes, personal communication),Electromagnetic surveys produce anomalous responses over the massivesulphide zones butabundant minor faulting “hat is common throughoutthearea creates problems. Water-saturated fault gouge produces anomalies and fault offsets disrupt the c0ntinuit.yand intensity of theofanomalous response from a conductivemassive sulphide lens. Inducedpolarization showsmore promise as an explorationtool because it appearsto discriminate between stratabound disseminated sulphide zones (stronglyanomalous) and zones of disseminated pyrite in t.he alteredhost rocks(moderately anomalous). The cost reconnai,ssanceof induced polarizationsurveys in this ruggedterrane would beprohi.bitive, but the techniquemight be applied effectively over small grids as a preludeto trenching in areasof widespread or deep overburden.

GENESIS

The veindeposits of thearea are clearly epigenetic, but. theprocess of formation of the stratabounddeposits is less obvious.Stratigraphic relationshipssuggest that the chert-carbonate lenses are synvolcanic. A

1 193 volcanicexhalative genesis can beargued for the banded massive sulphide lenses whichhave 'normal' precious metal concentrations but the forma- ation ofdisseminated precious metal-rich stratabound deposits may be morecomplex. c(MIcLus10Iss

TheSalmon RiverValley is oneof themost active exploration areas in British Columbiaand represents a distinctmetallogenic province in the region. The preciousmetal deposits occur in a variety of structural settings but all the major deposits are hostedwithin one thick andesitic unit in a differentiatedvolcanic sequence. The deposits can be classifiedaccording theirto geologic setting as (1) stratabound deposits ofundetermined origin and (2) epigeneticvein deposits. Major explorationprograms and prospectevaluation are expected to continue throughoutthe belt in 1983.

AcKNlmLEDGumTs

It is a pleasure to acknowledge the generoushospitality and logistical support of &so Minerals Canada, PacificCassiar Limited, Scottie Gold MinesLtd., and Westmin ResourcesLimited during visits to their operations. I am indebtedto Dane Bridge,Shaun Dykes, John Greig, Mike Kenyon, Paul McGuigan,and DavidWilliams for discussions about many aspects of thegeology and nineraldeposits of theregion.

John Mawdsley providedable assistance inthe field.

RJwmmicEs

Barr, D. (1980): Gold in theCanadian Cordillera, C.I.M., Bull.,Vol. 73, NO. 818, pp.59-76. Dykes, S. M., Meade, H., and Galley, A. (1982):Geology theofBig MissouriDeposit with Reference to Premier Silbak, G.A.C., Annual Meeting of theCordillern Section, February 19, 1982. Galley, A. (1981) : VolcanicStratigraphy and Gold-Silver Occurrences on the BigMissouri Claim Group, Stewart,British Columbia, University of WesternOntario, M.Sc. thesis, 181pp. Grove, E. W. (1971) : Geologyand Mineral Wposits of theStewart Area, B.C. Ministry of Energy,Mines S Pet. Res., Bull.58, 219 pp. Hanson, G. (1935) : Portland Canal Area, British Columbia,Geol. Surv., Canada, Mem. 175,179 pp. NorthernMiner, Esso Makes ImpressiveDiscovery on SilverButte's MissouriClaims, 1982, Vol. 68, No. 35, p. 1.

194 Tipper, H. W. andRichards, T. A. (1976): JurassicStratigraphy and History of North-CentralBritish Columbia, Geol. SJrv., Ca.nada, Bull. 270, 73 pp. White, W. H. (1939): Geology and Ore Deposition of Silbak Premier Mines Ltd., University of British Columbia, M.A.Sc. thesis.

195 HAPPING OF SILICA OCCUEREUC!ES IN BRITISE COLUMBIB

By 2. R. Bora

This project was startedin 1981and continuedduring the 1982 field season. The followingproperties not included in the 1981 survey were examinedfor information on size and quality:

(1) QUARTZITE UNITS

EX (82E/3E,49°00.5'-119006')

About 5 kilometressouthwest of Ezidesvillefine-grained cherty quartzitecrops out on severalsmall knolls over an area 200 metres by100 metres. Ihe quartzite is mostlymassive but has local quartz cementedbreccia zones. The surroundingrocks are dominated by phyllitic slate; however, siliceousbands and, less commonly, zones of fine-grainedmassive greenish grey volcanic rock occur. The rocksare part of thePermo-Triassic Anarchist Group.

WIN (930/2W, 55°02'-122054')

The quartzite from thisproperty, which is a medium grainedbuff to whiterock, is 150 metres wide andhas been traced for about 700 metres alongthe strike. It cropsout in the northern part of the summit of bunt Chingee.approximately 15 kilometres southeast of the Hart Highway between Fort McLeod andMackenzie. Numerous coarse-grained,massive white quartz veins of varyingwidths that strike mainlynorth-south cut the quartzite. Ihe surroundingrocks are blackslates and brown schistosegreywacke of the Cambrian (?) MisinchinkaGroup.

NONDA QUARTZITE (94H/14W, 53O57"12l027' 1

About100 kilometres east of Prince George a thick band of pure whiteorthoquartzite crops out approximately 3 kilometresnorth of the town of Longworth on thenorth side of theFraser River. The quartzite is massive and consists well-sorted,of well-rounded quartzgrains in a siliceousmatrix. ltvo parallelbands, each 100 to 250 metres thick,are separated by 300 a to 500-metre-thick sequenceof carbonate rocks. The carbonates are mainlylimestone, butdolomite is also present. Outcrops of the lowerband lieat elevationsbetween 1 000 to 1 150 metres, whilethe higher band is exposedin the upper part of the slopebetween 1 300 and 1 650 metres. Outcropsoccur for several kilometres. The quartzite is part of the Silurian Nonda Formation.

1 96 ROUNDTOP MOUNTAIN (93A/14E,52°55'-121018')

A 300 to 500-metre-wide quartzite band extends in a northwest- southeast direction fromRoundtop Mountain in the Car'ibooLake area. The quartzite is predominantly medium tofine grained and consists of well-roundedgrains. It is whiteto buff-weathering with mica flakes on foliationplanes. Theband continuesfor at least 15 kilometresalong strike, mostly atelevations between 1 OClO and 1 700 metres. The quartzite is part of the Hadryniarh/Cambrian Yanks PeakFormation.

YANKS PEAK (93A/14W, 52'51'-121°26')

A foldedband of massive, white, fine-grained quartzite crops ,out on Yanks Peak, 12 kilometresnorthwest of Cariboo Lake.The rock is composed of well-sorted androunded quartz grains in a siliceous matrix;tiny flakes of muscoviteoccur rarely. lhe quartzite, which is exposedover the area of approximately 300 metres by 500 m*stres, is apparentlyHadrynian (?).

MARYSVILLE (82G/12W, 49°36'-115057')

Medium tocoarse-grained massive quartzite 90 to 100 metres thick is exposed in the Perry Creekarea, 2 kilometres south ofMarysville. The range of quartzitecolours is from whiteto green and brown. White and light pinkrocks that constitute the upper part of the quartzitesequence consist of well-rounded,moderately sorted grains in a siliceousmatrix. The quartzite is part of the Calnbrian CranbrookFormation.

( 2) DYKE AND VEIN OCCURRENCES

SWAN (82E/12W, 49°43'-119054'1

Quartz on this property forms part of a pegmatite body that is exposedin scattered outcrops, road cuts, and trenchesover an area of approximately 60 metres by 120 metres. The property lies 27 kilometresnorthwest of Summerland at an elevation of 1 475 metres. The shaving is on a steepnortheast-facing slope and the vertical exposure of thepegmatite body is approximately 75 metres.In exposedareas, pure quartz constitutes approximately 25 per cent of thepegmatite body; therest is eithercontaminated by muscovite(10 percent), intergrown with feldspar (55 per cent), or composedof massivefeldspar (10 per cent).

FS (82L/13W,50°49"1 19'49' )

A milkywhite quartz vein crops out in two locations on Nisconlith Creek, approximately10 kilometres west of the town of Chase. A whitemassive quartz vein from 3.5 to 15 metreswide, wh:.ch is

197 exposedover the length of about 110 metres, comprises the southern outcropofthe north-south-striking vein. Occasionally, crystals developedthat are up to 30 centimetreslong and 15 centimetres in diameter. The quartzitein this area is quarriedfor industrial uses. The northernoutcrop is about 400 metresfrom the southern outcrop. The outcrop is dome shapedand consists of leucocratic granitic rock mt by quartzstockwork veining and a ZO-metre-wide quartzvein. The outcrop is 120 metres by 200 metres.

CAMPANIA ISLAND (103H/3W, 53O05'-129'25')

The silicaprospect is 160kilometres south of Prince Fupert on the westside ofCampania Island,about 1 kilometre from thecoast. 'Ihe mainshowing is a quartzoutcrop 105 metres by 35 metres in size thatrises 20 metresabove the surrounding terrane. "ne main component is milky white quartz;occasional fragments of granitichost rock occuralong the southern and northernmargins of the quartz exposure.Granitic inclusions are estimated to be less than 5 per cent. A smaller,parallel quartz vein is exposed 160 metreseast of the main showing. lhe vein is exposed in threenorth-south outcrops and is apparently 10 metres in width.

BANKS ISLAND (103G/8E,53"28'-130°02')

A numberof outcropsof pure white quartz occur near Patsy Cbve south ofPrince Fupert. The mtcropsare part of a northeastly trending body that is at least 20 to 30 metres wide. At thesouth- westernend of these outcrops the quartz is exposed in a 10-metre cliff. The quartz is massive,coarse grained, and milky white. 'Ihe quartz body is inCoast granodiorite intrusions, but the contact is notexposed so its real size and orientationare uncertain.

GLACIER CREEK (103P/13W,55O59'-129'55') plartzveins 3 to 9 metres wide are reported from severalold propertiesabout 5 kilometresnortheast of Stewart. cXlr recon- naissancestudy concentrated on veinsintersected in mnwell Mines Limited No. 4 adit and in theSilver Princess aditnorth ofGlacier Creek. However, veins in thearea are zones of predominantly quartz-argillitebreccia, rather than pure quartz.

MORRIS SUMMIT (104B/lE.56°13'-130005')

'A huge quartzlode' was reportedat a site 110 metres north of Scottie Gold Mines Ltd.'s 1 097 metreadit about 35 kilometresnorth of Stewart. 'Ihe exposureconsists of quartz vein breccia with many altered,rusty orange rock fragments.

198 MAPLE BAY (103P/5W, 55°25'-130000')

Thisarea provided a significanttonnage of quartzflux for the Anyox smelterduring the years of its activity. Maple Bay is located on the east shore of PortlandCanal about 56 kilometres south of Stewart.Nine major veinscrop out east andnorthceast of Maple Bay; theycontain variable amounts of sulphides. meFriday veinoccurs 25 kilometresnorth ofMaple Bay, about:500 metresfrom theshoreline. It consists of coarse-grained, milky quartz, is 4 to 5 metres wideand is at least 50 metreslong.

Fieldwork was carried out by 2. D. HOra and Jennifer Pel1 withGaorielle Suttonas a fieldassistant. Analysis of datacollected during the summer is currently in progress.

199 I'

200 OTHER IBVESTIGATIONS

RECENT MINERAL RESOURCE ASSESSMENT STUDIES m BRITISH COLUMBIA.

By K. E. Northcote K. E. Northcote L AssociatesLtd., Agassiz, British Columbia and W. R. Smyth and H. R. Schmitt B.C. Ministry ofEnergy, Mines and Petroleum Resources

INTRODICTIOU

A number ofmineral resource assessment studies were undertakenin 1982 toassist governmentplanning and decision making on landuse i.ssues. They were conducted inresponse to specific requests fromIands, Parks andHousing to create provincialparks, and from Forests andMunicipal Affairsfor coordinated land use planning programs. The aim of the studies was toidentify areas favourablefor mineral deposit discoveries and to ensurethat the planning process doesnot alienate such areas from explorationand mining. Summariesof four assessments are presented becausethey might be of use to theexploration industry in identifying andrating exploration target areas. Figure68 also shows thelocation ofother planning areas for whichassessment reports are inpreparation.

All thestudies were office-basedand carried out by K. E. Northcote undercontract to theMinistry of Energy, Minesand Petroleum Resources. Sincetheir completion, two ofus (W. R. Smyth and H. R. Schmitt)joined theMinistry andhave revised and added to the original reports. The reports will bereleased as open filesafter they have keen submitted to theplanning teams.

METHODS

Mineralpotential assessments of theplanning areas are qualitative. Mineralpotential ratings ranging from high (1) to low (5) were assigned tothe different geological units or packages in a study area., The ratingof each package was based on theoccurrence csf known rnineral depositsand its perceivedpotential for hosting undiscovered mineral resources. lhe types of mineraldeposits that may befound are discussed inthe text and theirpotential values estimated.

Parameters used to classify mineral potential include:

(1) Favourablegeological environments for mineralizatic'n.

(2)Production history of properties in the area and/orin similar geologicenvironments elsewhere.

201 Figrre 69. GaoIoq of Chi iko Lake DeferredPlanning Area.

202 ROCK UNITS OCCURRING IN CHILKO LAKE D.P.A.

203 (3) Known mineraloccurrences, regardless of present economic viability, because: (a) overburden may coverthe best mineralized zones (b)mineralization is three-dimensional;higher grade mineralization may occur atdepth

(4) Past and presentmining exploration activity; this is shownby the nunberand location of presentand former mineral claims, Crown grants,placer leases, etc.

The size of known and potentialdeposits in eachrating class is expressed on thebasis ofestimated total value of containedmetal. Classificationsare as follows: (A) large(greater than $1 billion); (B) medium ($50 millionto $1 billion); (C) small ($1 millionto $50 million).

Each report includesthe following:

( 1) A geologicalcompilation map at 1 : 250 000 scale or smaller.

(2) A mineraloccurrence map constructed from theMinistry's MINFILE, whichcategorizes occurrences according to size and typeof minerals present.

(3) A map showing thedistribution of mineralclaims that are in good s tanding.

(4) A mineralpotential map.

(5) A bibliographyofregional andeconomic geology reports for the studyarea.

(6) A discussion of thegeology of thearea with emphasis on major map units,structural features, and geologicalenvironments perceived to havemetallogenic significance.

(7) A discussion of the potentialtypes of mineral deposits expected in eachunit and estimates of theirpotential values.

(8) &pending on the optionsavailable to the planning team, recommen- dationsfor future fieldwork.

CHILKO lAKB PLANNING AREA (92N. 0)

INTRODUCTION

The olilko Lake DeferredPlanning Area (DPA on figures)lies at the easternedge of theCoast Range approximately 240 kilometresnorth of Vancouverand 150 kilometressouthwest of Williams Lake (Fig. 68). The areaextends from StikelanCreek on thewest to TasekoLakes on theeast

204 andfrom thenorth end ofChilko Lake southward to Stanley Peak (Fig. 69). It encompasses more than 2 000 squarekilometres wit'o parts accessible by gravelroad from theChilcotin Highway to the nort:h.

GEOLOGY

The planning area straddlesthe boundary between the Coast Plutonic Complex on thesouthwest and the Intermontane Belt on thenortk,east. Figure 69 is a compilationof the geology of theplanning area after Tipper (1969,1978) and Woodsworth (1977). The Intermont,Ine Belt i.n the area consists three,of northwest-southeast-trending, fault-bounded blocksof Triassic to Cretaceoussedimentary andvolcanic rocks. Andesiticflows and associated tuffs and breccias constitute the bulk of thevolcanic rocks and these are intercalatedwith waterlain tuffs, siltstones,shales, minorsandstone, and carbonate rocks. These are unconformablyoverlain by scatteredoutliers of Miocen'eand Pli.ocene plateaulavas. Plutonic rocks emplaced in Cretaceous and Tertiary times are granodiorite,quartz diorite, and diorite. Theyform the main mass ofthe Coast MDuntainsand lie mainlysouthwest of the study area. How- ever,throughout the area relateddykes, stocks, and sills intrudethe volcanic and sedimentaryrocks.

MINERALIZATION

Most of the known mineral occurrences (Fig.70) are found involcanic andsedimentary rocks at or close to plutonic contacts and withinthe plutons. A significantporphyry-type copper-molybdenum prospect is hosted by a granodioriteintrusion and adjacent volcanic roclcs at TchaikazanRiver inthe southeast part ofthe planning area. The volcanicrocks structurally above thispluton are cut by quartzveins thathost free gold and tellurideminerals. These veins were discovered by H. Warren in 1945and have been re-examined and c.rilled on many occasionssince. The Pellaire prospect(Fig. 70), located about 7 kilometres southeast of the lkhaikazanproperty, consists of pyrite, chalcopyrite,gold, silver, and bornite mineralization shatteredin quartz veinsthat cut a granodioriteintrusion.

A number of molybdenum andtungsten occurrences have been known since 1910 at thenorthwest end of Franklyn Arm ofChilko Lake. Skarn-type mineralizationoccurs in Triassic limestones andlimy sedimentary rocks nearcontact with granodiorite intrusions. The best known is the IXisie prospect (92N/Zb, Fig.70)which contains chalcopyrite, pyrrhotite, molybdenite,silver, and scheelitemineralization.

MINERAL DEPOSIT MODELS AND MINERAL POTENTIAL RATINGS

Severalgeologic environments identified theinplanning area are favourablehosts for a variety ofmineral deposits.

205 ,".

Figre 10. Mineraloccurrences of Chiiko Lake DeferredPlanning Area.

206 (1) PorphyryCopper-Molybdenum (Gold) Deposits

Based on the Tchaikazan Riverprospect and theprssence of other porphyry-type prospects thatoccur in geologicallysimilar environ- mentsadjacent to the area, parts of thestudy area are judged to havehigh potential forporphyry-type deposits. The Fish Lake deposit, 6 kilometresto the northeast of thestudy area, contains 180 000000 tnnnes of0.25 per cent copper and0.51 grams gold per tonne(Wolfhard, 1976) and the Poisonmuntain prospect, 56 kilometresto the east, contains 170 000 000 tonnes of 0.34 pel? cent copper and0.016 per cent molybdenum,and 0.34 gramgold per tonne (Seraphim and Painboth,1976) . me most likelyareas for porphyry- typemineralization are within, atthe margins, and adjacentto post-tectonicintrusions. In thestudy area, units displaying these characteristics havebeen assigned a 2B rating(Fig. 71). the highestassigned in the area.

Flyre 71. Mineralpotential of Chi Iko Lake Deferred Planning Area.

207 (2) Gold-SilverEpithermal Vein kposits

The Warren-Charlieprospects on 'EhaikazanRiver are examples of epithermalgold-silver vein deposits related to intrusions of the CoastPlutonic Complex. Preciousmetal vein deposits of volcano- genicorigin are in calc-alkalicvolcanic sequences in other areas, particularlyclose to faults and siliceousvolcanic centres. Most ofthe study area is underlain by volcanicrocks with this favour- ablegeologic environment but because occurrences of this type are unknown in thearea, these units are assigned a moderate (38 OK 3C) potential.

The Alexisoccurrence, located on the west side ofChilko Lake (Fig. 70). is a limoniticbreccia stained with malachite in volcanic rocksclose to a majorfault. The trace of thefault zone is assigned a moderate (3B) potentialfor precious metal vein deposits (Fig. 71).

(3) Skarn Deposits

Areascontaining carbonate-rich rocks have moderate potential for discovery of additionalcopper, molybdenum, tungsten,silver, and gold contactmetasomatic deposits of the Daisie type. However, outside of theFranklyn Arm areaexisting geological maps do not reportother areas of limestone in proximityintrusions.to Consequentlyonly the Franklyn Arm area is assigned a high (2C) potential.

(4) Others

Areas of lkrtiary volcanicrocks are assigned lowa (4) mineral potential.Environments may existfor epithermal vein deposits or forbasal-type uranium depositsat erosional unconformities below thevolcanic rocks but no suchdeposits are known. Suitable environments may also exist forCarlin-type gold deposits associated with carbonate-bearingsequences. There is no informationto supportthis possibility but it shouldbeborne in mind while conductingmineral exploration in the area.

KAKWA PLAMlING AREA (93H, I)

INTRODUCTION

The Kakwa PlanningArea, located along the eastern slope of the Rocky Mountains, is bounded on the east by theAlberta border and on thesouth and west by thedrainage divide between the Arctic and Pacific drainage system (Fig. 68). The areacovers approximately 33 750 hectares. A road built in 1982 to gain access to a quartzite prospect at Babette Lake is the only roadinto the area. lbe area is characterized by highrugged mountains,glaciers, and rockwalls interspersed with wooded valleys and smallglacial lakes.

208 GEOLOGY

The planning area lies withinthe Rocky MountainFold and 'I'hrust Belt and is characterized by a thicksequence of Late Precambrian to rawer Cretaceousmiogeoclinal andplatformal carbonate and clastic rocks (Fig. 72) . The clasticrocks include conglomerates thrcugh sandstones andquartzites, and siltstones toshales and argilliteswith some carbonaceousand coaly members inthe upper part of the sequence. The carbonaterocks range from calcareousshales toshaly limestones, and massive limes tonesto dolomites. The rock units havebeen compressed and displacednortheastward by a series of thrustfaults.

Explorationcompanies have not been active in the area, pactlybecause of poor access and partlybecause the geology is known only on a regional basis from reconnaissance mapping by theGeological SVcvey of Canada (Campbell, et dl., 1973;Taylor and Scott, 1979). From th,?sesurveys the geologyappears to betypical of the Rocky MountainFold and Thrust Belt. Withoutthe benefit ofmineral exploration reports on the area, the followingdiscussion on themineral potential relies heavily on ccmmpar- isons withanalagous geological settings outsidethe planning areathat hostmineral deposits.

METALLIC MINERAL DEPOSITMODELS AND MINERAL POTENTIAL RATING

(1) Carbonate-HostedLead-Zinc Deposits

A major lead-zincdeposit (Robb Lake) and 16 smaller occurrences havebeen discovered in platformalcarbonate rocks of the Rocky MountainFold and 'Ihrust Belt in northeasternBritish Columbia. Thesedeposits occur in Evoniandolomites andlimestones at a facies changeor 'shale out' frommassive carbonate rocks in the southeast to shalycarbonate rocks in thenorthwest (Macqueenand Thompson, 1978).In the Kakwa Planning Area the upper Wvonian Palliser Formationundergoes a similar change and, by analogy, is an excellentreconnaissance target. The Robb Lake deposit, which occurs in a similar geologicenvironment 360 kilometres t.o the northwest,contains approximately 6.1 milliontonnes of 7.3 per cent combined Lead and zinc, giving a grossvalue of about $350 million. For thisreason, the Palliser Formation is designat,zd as 38 con the mineralpotential map (Fig. 73),indicating moderate potential for finding a medium-sized deposit.

Potentialalso exists for Mississippi Valley-type lead-zinc deposits in themassive carbonate rocks that crop out extensively i.n the studyarea. Although the Cambrian Mural Formationhosts lead-zinc mineralizationoutside of the study area, nometallotects have been recognized in thearea for this type of deposit.Consequently the carbonate units are designated as moderatepotent:.al (3) with no sizeclassification.

209 Flqre 72 G3olog of Kakwa Lake Deferred Planning A rea.

210 (2) Clastic-HostedSulphide Deposits

Barite-lead-zincdeposits hosted by Devonian-Mississippian clastic rocks are a majortype of depositin the miogeoclinalrocks of the Rocky WuntainFold and lhrust Belt (MacIntyre,1982). Although knmndeposits theinKechika Troughof northeasternBlritish Columbia arerestricted to the westernhalf of the RDcky MDuntain Foldand Thrust Belt, potentialexists for discovering this type of depositin the shale units of the study area. By analogywith the age of thehost rocks of the known deposits, Devonian shales in the study area are assigned a moderatepotential (3); athershales are assigned a lower designation (4) (Fig. 73).

Much ofthe western part of the study area is under'tain by Cambrian quartzites andsandstones of theWNaughton and M2:hto Ebrmations. Although these andother quartzites in the study are.3 are assigned a low potential (4), strataboundlead-zinc-silver mineralization occurs in rocks of similar ageand settingin other mountain belts, for example,Laisvall, Sweden (Rickard, et dl., 1979).

INDUSTRIAL MINERAL AND MATERIAL POTENTIAL

(1) ptartzite

Good qualityquartzite for industrial use for building stone and as a source of silica occurs in the WNaughtonFormation throughout the study area. The quartzite is massivewith uniform beds u:? to 8 metres thick. A quartzitequarry at Wishaw Lake nearBabette Lake is underdevelopment. This site was chosen1arge:ly because it is more accessiblethan many otherprospective sites. Preliminary marketsurveys by thedeveloper indicate that the quartzite has many desirable and aesthetic properties fOK use as building stone.

Good quality gypsum 15 metres thickoccurs in the mi.ddle part ofthe WhitehorseFormation 7 kilometres east of theplannhg area (Govett, 1961) . Thisformation crops out at the eastern margin of the planning area around Cecilia Lake; its gypsum potential is untested.

(3) Phosphate

Phosphatedeposits were discoveredrecently about 30 kilometres northeast of thestudy area in theTriassic Sulphur Mountain Formation(HefEernan, 1980). This formation extentis into the study area where its potential is unknown.

21 1 Flpre 73. Mineralpotential of Kakwa Lake Deferred PlanningArea.

21 2 ENERGY RESOURCE POTENTIAL

The PetroleumIlesources Division assessed the energy resource potential ofthe study area in a separatereport that is summarized brieflyhere.

(1) Petroleum and Natural Gas

Favourableareas for petroleum and natural gas accumulations occur in theFernie Groupand under theCecilia lhrust Plate. In the Kakwa PlanningArea, leases and permits partly cover areas of interestbut detailed exploration has yet to be undertaken.

(2) Coal

The southern limit of thePeace River Coalfield, currently under developnentto the northwest, crosses the northeast corner of the planningarea. Coal licences extend from thestu3y area north- westwardalong strike (Fig. 73). Detailedexploration has yet to be undertaken on licencesadjacent to and in thestudy area but it is underlain by thecoal-bearing Minnes Group.

SUMMARY

The Kakwa Planning Area presents gooda example of thedifficulties involved in assessingthe mineral potential ofan area with only a broad regionalgeological data base and no detailedprivate exploration reports. In this case the Ministry of herqy, Minesand Petroleum Resources recommended tothe planning team that a groundassessment of themineral potential (mapping, stream geochemistry, 1ithogeochemi.stry) should be carriedout prior to anyland use decision that wouldwithdraw land from exploration and mining.

FLOWILLS PLANNING AREA (93A/lW, 92P/16W)

INTRODUCTION

Flourmillsoeferred Planning Area (Fig. 68) centres 3n latitute 52 degrees 06 minutesnorth and longitude 120 degrees 20 minuteswest.. me planningarea encompasses 9 000 hectares of the southernportion of the QuesnelHighlands, a highlydissected plateau of moderatecelieE. It is bounded tothe north, east, and south by WellsGray Provincial Park, and onthe west by Spanishmeek. Elevations range from 1 100 metresalong SpanishCreek to more than 2 100 metres on Wells Gray Provincial.Park boundary.Pleistocene glaciation rounded peaks and leftextensive valley bottom till deposits.Several well-preserved, post-g:Lacial volcanic cones,cinder deposits, and flows that lie near the eastern boundary of theplanning area provided the impetus for a proposal by the Ministry of Lands,Parks andHousing toannex all, orpart of, the planning area to WellsGray Provincial Park.

21 3

GEOLOGY

Figure 74 is a generalizedgeologic map of theregion sllrrounding the FlourmillsWferred Planning Area. The area is underlainpredominantly by Lower Cambrianand younger metamorphosed rocks of the !SnowshoeForm- ation of theCariboo Group (unit7a). Dominant lithologies are brown and greyquartz-mica schist, quartzite, thin-bedded marble, qlartz-feldspar mica gneiss, andamphibolite pegmatite (Campbell, 1963; Campbell and Tipper,1971). Along thesouthern boundary, these rocks an3 a minorarea of Triassic Nicola Group metasedimentaryrocks are intruded by Jurassic and/or Cretaceous monzonite to granodioriteplutons, which, by proxirrtity, might correspond to thenearby Raft andBaldy batholiths. Superimposed onthe general geologic pattern just described are Miocene to Recent volcanicflows culminating in a number of well-preservedcones and bl.ocky lava flows. lhese are found inthe northwest and central to southwes:tern part of theplanning area. Pervasiveylacial deposits and recent alluvium limit rockexposures.

MINERALIZATION

Thereare no metallic mineraloccurrences inthe Flourmills Deferred Planning Area. Scoria and ashdeposits were investigated by a private company,mi-Ag Resources Ltd., kt no results are documented to provide anindication of economic value. A mica depositassociated with pegma- tites ofthe Snowshoe Formationadjacent to thenorthwes.: boundary was investigatedin 1930, buthas received little recentattent.ion.

MINERAL DEPOSIT MODELS

By analoqywith geological environments and mineraldeposits adjacent to theplanning area, a variety of mineralizationpossibilities exi.st: for FlourmillsDeferred Planning Area:

(1 ) Porphyry-style molybdenum or copper mineralizaticnrelnted to Jurassic/Cretaceousplutons. (2) mngsten-bearingskarn mineralization associated with Snowshoe Formation-hostedJurassic/Cretaceous plutons. (3) Disseminatedgold mineralization iron-carbonate-richin Triassic phyllites. lbese rocks may extendsoutheast from the Crooked Lake- MacKay RiverValley.

MINERAL POTENTIAL

Figure 75 shows mineral potential for theregion surrounding Flourmills DeferredPlanning Area. Mineralpotential was considered to be low prior to about 1980. Regionalexploration work, initiatedafter publication of Federal-Provincialregional geochemical silt sample data for NTS 92P and 93A. raisedthe designation ofmineral potential from low to moderate.

21 5

Highest mineral potential for porphyry and skarn mineralization exists in thesouth where number a of stocks intrude the Snowshoe Formation. Central and northernparts of theplanning area that are underlain by Snowshoe Formation require detailed geologic mapping todetermine whether gold-bearinggeologic environments extend southeast from CrookedLake- MacKay Riverinto the planning area. Consequently, these rocks are designatedas having indeterminate mineral potential. Areas covered by post-glacialvolcanic cones and lavaflows are considered to have low metallic mineral potential.

GEOTHERMAL POTENTIAL

Explorationforgeothermal resources is in its infancy in mitish Columbia;the Flourmills area has not been investigated. Deep-seated structurescontrolled Tertiary to Recent volcanism in thearea. There- fore,while geothermal energy potential presently is unknown, it couldbe high.

SUMMARY AND RECOMMENDATIONS

FlourmillsDeferred Planning Area covers 9 000 hectare!; of relatively unexploredland in thesouthern mesne1 Highlands. Recent exploration adjacentto the planning area indicates that mineral potential may be considerablyhigher than previously thought. Untested mineralization possibilitiesinclude molybdenum-copper porphyries,tungsten-bearing skarns, and disseminatedstratabound gold.

Industrialmineral potential is minlyfor scoria, ash, andmica. The economicsof these commodities, particularly scoria and ash,are dependent on proximity to readymarkets.

Geothermalenergy potential, which is generallyhigh in areas of!recent volcanicactivity, is untestedbut may prove to be significant.

At present, it is stronglyemphasized that the current level of geologic knowledge forthe Flourmills Deferred Planning Area needsenhancement by more detailedgeological, geochemical, and geothermalsurveys to permit considerationand endorsement of proposals to alienate laridfrom exploration and development.

SOUTH MORESBX PLANNING FmJ3A (103B, C; 1020)

INTRODUCTION

The South Moresby Planning Area is located on thepleen Ckarlotte Islands approximately 200 kilometressouthwest of Princempert. The planning areacovers 145 270 hectares and includesall land and adjacentislands south ofan east-west-trending boundary south of TangilPeninsula. The

21 7 pleen Charlotte Ranges are thedominant physiographic unit, with the San Christoval Rangesforming the major subdivision. Elevations range from sea levelto more than 1 100 metres. Alpineconditions extend locally to near sea level.

Duringthe Pleistocene, tbresby and adjacent islands were intensively glaciated as evidenced by widespreadand varied glacial featuresin mountainous areas. Some paleoecologists thinkthere were glacialrefugia becausenunataks existed even during the maximum stage of glaciation.

Dailyflights fromVancouver toSandspit andtwice-weekly ferryservice fromPrince Rupert provide access to the meen Charlottes. Access tothe planning area is by boat, seaplane, orhelicopter. Limited access by loggingroads is available on parts of Lye11 Island and oldmining roads and trails are still discerniblenear Jedway.

The Environmentand Land Use Committee (ELUC) initiatedthe South Moresby ResourcePlanning Program in 1979 inresponse to numerousproposals by publicinterest groups for establishment of a largewilderness park, and inresponse to native Haidaconcerns about proposed logging on Burnaby Island. Ihe Environmentand land Use Committee terms ofreference called for a five-yearmultiple land use allocationplan to be produced. Mineral resources were among the many issues that the planning team addressed. The Ministryof Energy, Mines andPetroleum Resources' major input to the planningprogram during the last two andone-half years consisted of the following:

District Geologist or Mineral Land Use Geologistparticipated in monthly meetings. MineralPotential Evaluation Report (1981) prepared by K. E. Northcoteof Bema IndustriesLtd. MineralResources Wchnical Report, includinganeconomic evaluation,written by K. E. Northcoteof K. E. Northcote & Associates Ltd., and ResourceData and Analysis Division. Close liaison keptwith mining companies actively working in the area and theBritish Columbiaand YukonChamber of Mines. Proposalsfor one sizeable and two small ecological reserves evaluated.

The planningprogram meetings will conclude in early 1983.Following a final set of publicmeetings, a series ofland use options supported by extensiveresource evaluations will be presented to themvironment and Land Use Committee. A policydecision will follow.

GEOLOGY

A. Sutherland Brown, from1958 to 1963, geologically mapped the pleen CharlotteIslands at ~a scale of1:125 000. The results of his work, which are documented in Bulletin No. 54, arethe basis for all subsequent

218 geologicalstudies andmining exploration on theislands. Recent explorationfor gold deposits that are similar to the Cinola deposit on Graham Island provide further detailed geologic data.

The stratigraphicsection on Moresby Island is fairlyconplet,e and similartothat theofother ween Charlotte Islands. Three major periods ofvolcanic activity are separated by fourperiods of deposition offossiliferous marine sedimentary rocks. Two periodsof plutonism are present,Iate Jurassic syntectonic intrusions and IateTertiary post- tectonicintrusions. Volcanic and plutonicrocks have evolved with time, frombasic to acidic, from quartzpoor to quartz rich (Sutherland Brown, 1968).

A continuouslinkage of northwestward-trending fault systems dissects the islands.These major crustal fractures dominated the tectonicdevelop- mentand controlthe distribution of rocktypes. The Rennell-Louscoone fault zone,active predominantly from Iate Jurassic to Cretaceous time, extendsthroughout the planning area fromLye11 Island :tn thenorth to KunghitIsland in the south (Fig. 76).

A diversityof geologic environments for mineral deposit formation exist. Thewide variety ofvolcanic and sedimentary rocks; the syntectonic and post-tectonicplutons, dykes and sills; and thelarge deep-seated faults on Moresbyand adjacentislands can all create environmtznts favourable formineral deposition.

MINERALIZATION AND MINERAL DEPOSIT MODELS

FrancisPoole discovered chalcopyrite and magnetitemineralization in South Moresby Planning Area in 1862 in thevicinity of Skincuttle 1:nlet. Forthe next 80 yearsexploration intensity fluctuated and there was limitedproduction of primarilycopper-bearing ores.

(1) ContactMetasomatic Deposits

From thelate 1940's to 1970 attentionfocused on (exploration and developmentcontactof metasomatic (replacement) iron-ctopper depositswith accompanyinggold and silvervalues. The foll.owing featurestypify these deposits:

(a)Proximal to the contact of massivelimestone of the KungaForm- ationwith altered basalts of theKarmutsen Formation. (b)Pdjacent to a plutonic body. (c)Faulting, pre-ore diorite porphyry andabundant .post-ore dlykes. (d)Brecciation and common presence ofa skarnenvelope. (e) Orebodiesoccur in tabular-lensoidto pipe-like deposits that areconcordant or discordant to bedding andconfsist of massive magnetitewith variable amounts of chalcopyrite,pyrite, and pyrrhotite.

219 SYMBOLS

PRINCIPALFAULTS AND LINEARS: DEFINED, APPROXIMATE, ASSUMED ...... ,.. DEPOSITS AN0 OCCURRENCES ......

MINES...... X

Figure 16. Majorfaults and linears showing relationship to known mineraldeposits and occurrences,South Moresbj Planning Area.

220 Jedway, thebest known ofthese deposits inside the planning area, producedover 2 milliontonnes of iron concentrate frcm 1962 to 1968 with a valueof more than $21 millionand provided direct employment for up to 150workers. Significant reserves remain in other nearby deposits.

(2) Gold Deposits

Thediscovery of the Cinola gold deposit on Graham Island by :=rem Specognaand John Trico in 1970 stimulated a widespreadsearch for similar deposits. They occur insilicified deep-seated faults and shearzones and are interpreted as variations of theCarlin Nevada- typeof deposit. Exploration concentrated first on Graham Island aroundthe original discovery and then, predictably, spread to similar geologicenvironments on Moresbyand adjacentislands.

The Cinola golddeposit is located on the west sideof theSandspit fault where Haidasandstone and shale are structurally over1a:tn by EarlyTertiary volcanic rocks. Poorly lithified Mio-Pliocene sandstone,shale, and conglomerate of the Skonun Formaticnoccur on the east sideofthe fault. Rhyolite porphyry crosscuts sedimentary units. Goldand silvermineralization is localizedinintensely silicifiedrocks and quartzveins that appear tc'be spatially relatedto the rhyolite porphyry. Barr (1980)published estimates ofreserves that ranged up to 22 million tonnesaveraqing 2.49grams goldper tonne; recent conpany reports state reservesin the order of 41 milliontonnes with 1.9 grams gold per tonne.

Gold exploration in the planning area involves a fairly wide variety ofrock types but a narrowrange of mineralizing environments. The following are significant as explorationguides:

(a) Silicification andquartz veining accompanied by sulphides proximal to deep-seated faults, shear zones, and major fault splays. Major fault systemstraverse the cueen Charlotte Islands fromnorthwest to southeast (sutherland :3rown, 1968). (b)Silicification andsulphide mineralization that is associated withTertiary (?) andesitic to rhyolitic dyke swarms. (c) Silicificationin brecciated rhyolitic rocks near eruptive or collapsecentres; these likely targets are areasof Tertiary (Massett) volcanism. Dyke swarms withinthese volcanic rocks mightalso be significant.

Companiesdiscovered significant mineralization on northern Lye11 Islandand on Moresby Islandnorth ofBigsby Inlet. Some miner- alizedzones may extend more than 1 kilometrealong well-defined faultstructures. Exploration for golddeposits inthe planning area is in its early stages; we anticipate rmchmore tofollow.

221 METALLICMINERAL POTENTIAL Area Class SOMEDEPOSITS KNOWN; TYPE OF OCCURRENCE AN0GEOLOGICAL ENVIRONMENT FAVOURABLE: SOME EXPLORATION AT ADVANCED STA- GES: CONTINUEDEXPLORATION

NO SIGNIFICANTDEPOSITS KNOWN; GEOLOGICALENVIRONMENT FAV- OURABLE:PRESENT AND FUTURE EXPLORATIONLIKELY

SOME INDICATION OF MINERAL POTENTIAL:GEOLOGICAL STATUS INDETERMINATEAT PRESENT; EX- PLORATIONPOSSIBLE

Fiyre 11. Metallic mineral potential of SouthMoresb/ Planning Area.

222 volcanogenicMassive Sulphide Deposits

Massivevolcanogenic sulphide deposits and gold mineralization may occurin the predominantly acid submarine volcanic sequence of the Yakoun Formation.This possibility remains virtually untested, partlybecause areas underlain by the Yakoun Formation are not extensive.

Post-TectonicPorphyry Systems and Gold-Bearing Veins

Post-tectonic intrusions merit exploration for differentiated copper and molybdenum porphyrysystems as well as goldd.eposits. The Catfaceporphyry copper-molybdenum depositand Zeballos gold-be.sring quartzveins on Vancouver Island are examplesofmineraliz.stion relatedto similar post-tectonicintrusions in a similar geologic terrane.

Other Possibilities

Otherpotentially economictypes of mineralizationinclude c'opper and lesser vanadium in amygdules inthe tops of Karnutsen vokanic flows,and paleoplacer deposits proximal to areasofgold mineralization.

MINERAL POTENTIAL

In 1981, undercontract to the Ministry, K. E. Northcote,then with Bema IndustriesLtd., prepared a mineralpotential map at scale 1:125 000 for theplanning area. The map was compiledfrom Ministry file?s and informa- tionprovided by industry. General conceptsof mineral potential outlined earlier were utilized. A reduced,slightly modified version of this map is presented on Figure 77.

Mineralpotential is summarized as follows:

All areas where Kunga or interlavalimestones are incontact with Karmutsen volcanic rocks, and are cut by or are close to intrusions, are considered to be areas ofhigh (2) potential for iron,copper, gold,and silver mineralization in the formof contact meta-som,stic deposits . Areas thatare underlain byany of thefeatures descr:.bedprevi'3usly under'Gold Deposits' are classified as havinghiqh to modmerate potential (3 to 2) forgold deposits. Ongoing exploration will necessitateperiodic map revisions; some Class 4 areas will b,ecome Class 3, and some Class 3, Class 2. Areas underlain by the Yakoun Formationand post-tectonic intrusions are classified as havingmoderate potential (3) forvolcanogenic massivesulphide deposits and porphyry systems respectively. Syn- tectonicintrusions are assigned low mineralpotential (4). Deep emplacementand lack differentiationof make them unfavourable explorationtargets.

223 SUMMARY AND RECOMMENDATIONS

For 120 yearsthe South Moresby Planning Area hasexperienced varying intensities of mineralexploration andproduction of ore. Prior to 1980 most of themineral exploration concentrated on searchingfor contact metasomatic(copper, iron, gold, and silver) deposits.Exploration for thesekinds of depositshas reached a maturestage, as attested by the nmber of known properties in thisgeologic environment. Even now, con- siderablescope exists for expanding known reserves. In theearly 1960's more than $1 million was spentexploring for such deposits inthe SkincuttleInlet area andculminated in the mining of the Jedway iron deposit. It is probablethat producers will develop new minesfrom these kinds of deposits on southern Moresby Island or Burnaby Islandin the future.Geologic environments which may hostcontact metasomatic depositsshould, therefore, be protected from alienation.

Discoveryof Cinola (gold) deposit on Graham Islandstimulated explorationin similar geological environments in the planning area. Work is in its initialstages but results obtained to datein areas such as Lye11 Island,have proved encouraging. Exploration inthe near future will likely be focusedon areas close tothe major fault systems that extend southeasterlythrough the length of theplanning area.

The South Moresby Planning Area program presented a majorresource plan- ningchallenge. Many areas of highmineral potential and undeveloped depositscoincide with areas highof scenic, ecological, and core recreationpotential. lhe main thrustof this Ministry's involvement has been to documentresource values, analyse conflicts with other resources, andensure that mineral resources are fully,consideredin the range of optionspresented for a decision.

REFERENCES

Barr, D. A. (1980) : Gold inthe CanadianCordillera, C.I.M., Bull., Vol. 73, No. 18, pp. 59-76. B.C. Ministry ai Energy, Mines & Pet. Res., Assessment Repts. 271,3131, 3271,3319, 3427, 3507, 3948, 3949, 5357, 5719, 7156, 7574, 8295, 8682,9231; RevisedMineral Inventory Map 93A (MI), plesnel Lake. Relik, G. C. (1981): Geologicaland Geochemical Report on the Frasergold Property,Cariboo Mining Division, British Columbia, 93A/7E, Keron HoldingsLtd., B.C. Ministry of Energy,Mines & Pet. Res., Assess- ment Rept. 9751. Campbell, R. B. (1963) : Geology,plesnel Lake (East Half), British Columbia, Geol. Surv.,Canada, Map 1-1963. Campbell, R. B., buntjoy, E. W., and Young, F. G. (1973): Geologyof McBride Map-Area, British Columbia, Geol. Sbrv.,Canada, Paper 72-35. Campbell, R. B. andTipper, H. W. (1971): Geology ofEmnaparte Lake Map- Area, British Columbia, Geo.2. mrv., Canada, Mem. 363.

224 Chevalier, A. (1981):Assessment Report on the Rock Sam.@lingShrvey of the lhree Mineral Claim Groups inthe lreka Property, Cariboo MiningDivision, 93A/7, Lhnex Inc., B.C. Ministry a? Energy,Mines & Pet. Res., Assessment Rept. 9786. Davis, N.F.G. (1930): Clearwater Lake Area, E%itishIblumbia, Geol. Surv., Canada, Summ. Rept.,1929, Pt. A, pp. 274A-29dA. Fahrni, K. C. (1961): Ekplorationand Reserves, Jedway Iron-OreLtd., Harriet Harbour,pleen Charlotte Island, unpub. rept., 9 pp.and maps. Govett, G.J.S. (1961):Occurrence and Stratigraphy of !SomeGypsum and Anhydrite&posits in Alberta, Research Council, Alberta, Bull.. 7. Heffernan, K. J. (1980):Report on Geological Mapping., Samplingand Drilling, WAPITI 1-25 Claims, LiardMining Division, B.C. Ministry of Energy,Mines & Pet. Res., Assessment Rept. 8407. Holland, S. S. (1964): Landforms of British Columbia, A Physiogi!aphic Cutline, B.C. Ministry of Energy,Mines & Pet. Res., Bull. 48. MacIntyre, D. G. (1982) : Geologic Setting Recentlyof Discovered StratiformBarite-Sulphide Deposits in Northeast British Columbia, C.I.M., Bull., Vol. 75, No. 840, pp. 99-113. Maqueen, R. W. and Thompson, R. I. (1978):Carbonate-Hosted Lead-Zinc Occurrencesin Northeastern British Columbia with:mphasis on the Robb Lake Deposit, Cdn. Jour. Earth Sci., Vol. 15, No. 11, pp. 1737-1 762. Mellin, R. G. (1930):Report on the Clearwater Mica Mine, B.C. Mi.nistry of Energy,Mines & Pet. Res. Northcote, K. E. (1 981) : Mineraland Ekploration PotMonkman Pass[93I), Map-Area, NortheasternBritish Columbia, Geol. Surv., Canada,@en File Map 630.

8 225 Tipper, H. W. (1 969) : Mount Waddington, Geol. Lhrv., Canada,Paper 68-33...... (1978):Taseko Lakes (920) Map-Area, Geol. Surv., Canada, Map 534. Wolfhard, M. R. (1976): Fish Lake, in PorphyryDeposits of theCanadian Cordillera, C.I.M., Special Vol. 15, pp. 317-322. Woodsworth, G. J. (1977) : Pemberton(92J) Map-Area, Geol. Surv., Canada, open File 482. Young, F. G. (1978) : The Lowermost Paleozoic McNaughton Formationand EquivalentCariboo Groupof Fastern British Columbia,Piedmont and Tidal Complex, Geol. Lhrv., Canada, m11. 288.

226 SILVER-GOLD ZONATIOU IN ME LASS VEIN SYSTEW, BEAVERDKLL CAlp, SOUTH-CEWTRAL BRITISH COLUMBIA ( 82E/6E)

By P. H. Watson Indianand Northern Affairs Canada, Whitehorse, Yukon Territory and C. I. Godwin Department of GeologicalSciences, 'Ihe Universityof British Columbia

INTRODKTION

The Beaverdellsilver, lead, zinc (gold) vein camp (Fig. 781, in the southern part of the Cmineca Crystalline Wlt insouth-central Ehitish Columbia,has been a silverproducer since the turn of the century. In recentyears some goldhas been reported in the eastern, and deeper, end ofthe Lass veinsystem (Lower Lass mine; 8. Goetting,personal communication,1979). 'Ihis study was initiated to examine the distribut.ionof major andminor elements in the Upper (Highland) Lass and Lower Lass vein systemand to describethe zoning patterns, with emphasis on the eaonomi- callyimportant gold and silver.

The area is Underlain by granodiorite of theWestkettle batholith, which hasbeen intruded by theBeaverdell quartz monzonite stoc'k (Fig. 78). Ihe granodioritecontains remnant pendants and/or screens of metamorphosed volcanicand sedimentary rocks of the Wallace Formation(Reinecke, 1915; Christopher,1975a, 1975b, 1976). A detailed summary of the geology is given by Watson (1981)and Watson, et dl. (1982).

GE0uX;y

Mineralization is found in a northeast-trending3-kilometre by 0.8- kilometrebelt, referred to as the Beaverdell mine area, on the west slope of Wallace Mountain(Kidd and Perry, 1958). From westto eas,t, the major producingmines were: Wellington,Sally, Bell,, Highland Lass (Upper Lass), and Iower Lass (Fig. 78). 'Ihe Upper and :bower Lass mines are presentlybeing operated by lbckCorporation Ltd., and the samples collectedfor this study are from these and related workings.

Most of theveins are hostedin the JurassicWestkett:le granodiorite. Some mineralization is also found in the Older Permj.an (?) Wallace Formationgneissic rocks, which overlie the batholith at theeastern end ofthe mine area, althoughstructures tend to horsetail and dispersein thesegneisses (Goetting, personal communication, 1979). Despite the apparentlack ofmineralization ir. the younger,Terti.ary, Beaverdell stock, which intrudes the batholith at the westernend (of the conlplexly

227 faulted mine area, K/Rr andgalena-lead isotope studies demonstrate that theveins are genetically related to the Beaverdell stock (Watson, 1981; Watson, et dl., 1982).Propylitic alteration is found in thewallrock up to 8 metres from the veins (R. Verzosa,personal communication, 1979) and thinsections of this alteredgranodiorite show amphibolesalmost entirelyconverted tochlorite, and feldsparsreplaced by clay and calcite.

The mineralizedveins occupy fissures along east-trending faults in the western part ofthe mine area andalong northeast-trending faults in the easternportion of the system (part of Bell, Upper Lass, and Lower Lass). Veins rangefrom a few centimetres to a metre in width,and average 0.3 metres (White,1949) but are rarely continuous for more than 5 to 10 metres withoutoffset. However some ore shoots show onlyminor offset overhorizontal distances up to 150 metres(White, 1949). The extensive faultinghas been classified by White(1949). The mostimportant type of post-orefaulting is highangle andnormal. A series ofwidely spaced, northnortheast-striking,to southeast-dipping faults divide the mineralizedsystem into large blocks, often with up to 100metres of verticaldisplacement between them. The West Terminalfault, separating the Bell and Lass mines, and the East Terminal fault, separating the Upper and lawer Lass mines, are of this type (Figs. 78 and 79) . The veinsare chopped into small segments by northeast-striking,closely spacednormal faults, which flatten the dip of thevein from 50 to 34 degrees(White, 1949). These faultsdip to thenorthwest, and generally show less than a metre displacement.

Major metallicminerals in the veins are galena, sphalerite, and pyrite, with lesser amounts of arsenopyrite,tetrahedrite, pyrargyrite, chalcopyrite,polybasite, acanthite, nativesilver, and pyrrhotite(Reinecke, 1915;Staples and Warren, 1946a, 1946b; Watson, 1981; Watson, et dl., 1982). The gangue material is mainlyquartz, with some alteredwallrock fragmentsincluded in thevein; small concentrations of calcite and fluorite are also foundoccasionally. Some supergenesilver mineralization is present,chiefly as nativesilver wires and plates. However, most of the mineralization is of hypogene origin(McKinstry, 1928; Staples andWarren, 1946a, 194613). Supergenematerial is notconsidered in thisstudy.

DATA CoLLpCTIoll AUD AEALYSIS

Bulk chip andhand samples of vein material within the granodiorite were collected from209 locations in the Lass system (Fig.79). A systematic samplespacing was notpossible due to veingeometry, so veinmaterial was chipsampled wherever accessible thein workings. Samples from mined-out areas were takenfrom the edges of oreshoots.

Samples were analysed by atomicabsorption spectrophotometry at the Departmentof Geological Sciences, "he University of British Columbia for zinc,lead, iron, copper, cadmium, silver,calcium, magnesium,manganese,

228 cobalt, and nickel.Gold, arsenic, mercury, and antimony were a.nalysed for by Min-En LaboratoriesLtd., NorthVancouver, Earitish Columbia. Resultsare in Table 1. Duplicateanalyses sample:;of were evaluated usingthe methodof Thompson and mwarth(1978). The followingi:ldicate theprecisions for each element (at average concentrations) determined by this method: (1) between 5 and 10 per cent:copper, catdmium, antimony, arsenic, andmanganese; (2) between 10 and 20 per cent: zinc,lead, calcium,and magnesium; (3) between 20 and 30 percent: silver; and (4) between 40 and 45 per cent,gold. Precision for elements estimated as the mean relativeerror rather than as a functionof concentration as in the 'Pnompson andmwarth method are:nickel, 10 per cent; iron, 35 per cent;cobalt, 38 per cent; andmercury, 120 per cent.

The truespatial relationship betweensamples atthe time ofemplacement cannot be seen usingthe mine plan viewbecause of post-orefaulting. Therefore, the veins were palinspasticallyreconstructed by removing the movement alongmajor faults. Since most mining was ca.rriedout on the fault-boundedsegments of thevein, the oreencountered along a drift couldrepresent either a series of parallelveins or progressively lower sections ofthe same vein.Within the fault-bounded, major sections, therefore, it is assumed that successivesamples represent a [general continuation of themajor vein system, down dip. Thisreconstructed plane may beup to 100 metres thickin some areas,because not all movement hasbeen removedand themineralization probably occurs within a series of subparallelveins. Inthis study, however, thisplane is consideredto represent a singlevein, or a series of veinsfor whichan overallzoning pattern can beexamined. Figure 79 shows thesample locations on thecomposite plan of theworkings. The reconstructed plans,used for all subsequent interpretations, are shownon Figures 80 to 84. Changes in element content down thedip of the vein can be examined by projecting all pointsonto an east-west line (approximately down dip), and plottingvalue versus distance along this line. These plots,called section plots, are shown withreconstructed plans on Figures 80. 81,and 84.

INTEWREIATION AND DISCUSSIOU

Histograms show thatall elements havelognormal distril3utions. Nickel and cobalt are often not present in detectable quantities and will not be consideredfurther. Poor reproducibility formercury analyses makes their use suspect,but mercury will be discussedbecause of its importance in many ore-formingenvironments.

Each elementcan be partitioned into populations using lognormal prob- abilityplots as outlined in Sinclair(1976). 'Pnree populationscan be definedfor silver and lead, andone for mercuryand calcium. All. other elementscan be partitionedinto two populations. The means, standard deviations, and population proportions arelisted in Table 1.n2. this tableelements aregrouped on therelative proportions anomalousof

229 population (A) andbackground populations (B and B') . The lower two silverpopulations show a splitsimilar to zincand cadmium, while the mostanomalous population is proportionatelysimilar tocopper and arsenic. This suggeststhat the mostanomalous silvervalues may be associatedwith copper and arsenic minerals such as sulphosalts, while themoderately anomalous concentrations of silverare associated with base metal mineralssuch as galenaand sphalerite. Golddoes not have populationproportions similar to any otherelements (Table 2). It is possiblethat only onegold population is present and thatthe 10 per cent backgroundpopulation represents a bottomtruncation of the data due tothe detection limits ofthe analytical equipnent used (Sinclair, 19713, ratherthan a secondpopulation.

Correlations are generallyonly applicable to single population variables. The large amount of overlap(estimated 30 to 70 percent) among populationsformost of theelements, however, allows the use of correlationsto show approximaterelationships. A correlationmatrix of logtransformed data (Table 3) shows strongcorrelations at the 0.1 significancelevel between the elementszinc, lead, iron, copper, cadmium, silver,gold, and antimony. The gangueelements, manganese, magnesium,and calcium, show strongcorrelations with each other. Calcium shows negativecorrelations with silver and arsenic,while magnesium correlatesnegatively with copper, antimony, arsenic, and gold. Ranked onstrength of correlation,silver correlates with lead, zinc, copper, iron,antimony, gold, cadmium,and arsenic. For gold,thestrongly correlated elements are, inorder: iron, lead, zinc, copper, cadmium, antimony,arsenic, and silver. %is suggeststhat silver is associated withgalena and sphalerite and, to a lesser extent,with antimony sulphosalts. Gold correlatesmost strongly with iron minerals, followed by the majorsulphides, galena andsphalerite. Thus,gold is primarily associatedwith pyrite and/or chalcopyrite; arsenic andantimony minerals,while significant, appear to be less important.Correlations forthe three indicator elements, mercury,arsenic, and antimony are: (1) mercury correlates with antimony,copper, zinc, lead, and cadmium; (2) arseniccorrelates with antimony, gold, iron, silver, andlead; and (3) antimonycorrelates with iron, lead, copper, zinc, gold, mercury, arsenic, cadmium, and silver. From this, it appears thatantimony is the mostdominant of these three indicator elements. Because much of the correlationmatrix simply shows theaffinity of allthe sulphides for eachother, some correlations would beexpected even if the minerals they represent were notcontemporaneous. Antimony, however, seems to correl- atewith all ore-forming elements and was a more significantelement than arsenic in the vein-forming solutions.Detailed studies of themineral- ogy (Staples andWarren, 1946a,1946b; McKinstry, 1928) show that pyrargyrite and tetrahedrite(antimony endmembers) are the common forms oftheir respective solid solution series in this veinsystem. Arseno- pyriteprobably formed earlier thanother ore minerals such as galena and sphalerite (Watson,1981).

Spatial relationships among populationscan be seen when theassay values (Table 1) are computer-drawn,using different symbols for background and

230 anomalousvalues, on the reconstructedplan and section plots of Figures 80 to 84.Anomalous valuesfor silver occur mainly in the cemtral, westernportion of the mine. By comparison, the 10 :?er Cent of the valueswhich form thebackground population for gold 1i.e mainly in the western part of the mine (Figs. 81 and 83).

Differencesin values between the upper,western and lower, eastern parts ofthe mine are clear on Figures 82 and 83. The highestvalues (approxi- matelyone-quarter of the samplepoints) for zinc, lead, and gold are in theeastern part ofthe vein system. Plan and sectionplots on Figure 84 show that ratios of gold to silver are dramaticallydifferent in t:he two parts of the veinsystem; 17 of the highest 20 valuesfor gold/silver are inthe eastern section, and thehighest 50 valuesfor silver/gold are in the westernpart ofthe mine.

The two segments,defined previously, were split into tw3 equalsections (based on distance down dip) to see if smaller subdivisionsin the zoning pattern were present. Means, withstandard errors, for the four subdivisions are plotted on Figure 85 alongwith the same statistics using only two subdivisions of the vein.Three of the fourelements (lead, silver, and gold) show levelsections and sharpchanges indicating that valueswithin each of the two major sections are similar, but that major changesoccur between the two sections. Thus, Figure 85 is consistent with only two majorzones inthe mine.

A north-trendingline between high silver, moderate lead and zinc in the west, and low silver,high gold, andmoderate to highlead and zinc in the east is drawn on Figures 80 to 85. Thisline is placednear the central part of the mine, about 120 metres east of the East lkrminal fault.Figure 86 summarizes the changesacross the line as notedabove or as detailedin fluid inclusion, mineralogy, andgeometry studies by Watson ( 1981 ) .

Because ofthe difference in the number of samples pn either side (of this dividing line (N = 159 to the west and N = 42 to the east), t-tests and F-tests were performed todetermine if, indeed,the two populations are significantlydifferent (-C= 0.05). The followingelements (logrithmic) havesignificantly different geometric means (t-test) andvariances (F- test) in the two parts of the mine: gold,zinc, leiid, cadmium, and mercury.Vein thickness (arithmetic) alsohas significantly diEferent meansand variances on eitherside of the dividingline. Gold, zinc, lead, cadmium, andvein thickness means are higherin the eastern .part of the mine whilesilver and mercury means are higherin the: west.

CONCLUSIONS

The presence of silver-goldzonation in the Lass veinsystem has been known to existfor several years (B. Goetting,personal communication, 1979;Christopher, 1975a, 1975b). This studyhas examined the majorand minorelement distribution patterns in samples from the Lass veinsystem

231 hosted in the Westkettle granodiorite. lhevein system was palinspasticallyreconstructed into a singleplane by removing the movement along majorpost-ore faults to examine theoriginal element zoning. Fifteen elementshave been studied (zinc, lead, copper, iron, manganese, cadmium, calcium, magnesium, cobalt,nickel, gold, silver, mercury, arsenic, and antimony), all of whichcan be partitionedinto 1, 2, or 3 lognormally distributedpopulations. The correlation matrix of elementsindicates that silver associates withgalena, sphalerite, and antimony sulphosalts, but that gold associates with pyrite andchalcopyrite.

The fourmajor economic elements, zinc, lead, silver, and gold.have been consideredin detail. Plan views shw a series of oreshoots, elongate alongstrike, en echelon down thedip, in the upper part of thevein system.Metal zoning and mineral deposition are related to depth and reflect changes in temperatureveinor configuration specificat elevations.

Two zonesof distinctivemineralization are recognized in the Iass vein system. lhe boundarybetween these two zonestrends north-south and lies withinthe Lower Lass mine, about 120 metres east ofthe Qst Terminal fault. In contrasttothe lower, eastern part, theupper, western portion of the veinsystem is characterized by high silver andmoderate zincand lead values, more gangue,and thinner veins within multiple vein andstringer zones. The lower, east endofthe vein system, hwever, containshigh gold, moderate to highzinc and lead, and lw silver values. The elementscopper, calcium, magnesium,and arsenicshw consistentvalues throughout the mine.

Goldvalues are concentrated at depth and in several small zonesalong thefootwall of thesystem. Silver values are highestin the upper parts ofthe system, centrally between the footwalls andhanginqwalls. Using informationfrom a fluidinclusion study (Watson, 1981)' the gold mineralizationcanberelated to solutions higherof temperature, salinity, and pressure. This model postulates thatgroundwater mixing occurredabove a throttlingpoint, resulting in lower temperature, lower salinity, andlower pressure solutions that deposited thesilver mineralization. A model for element zonation in this system,based in part onthe fluid inclusion studies, is shownon Figure 86. lhis model accountsfor: (1) thepresence of only two zones(above andbelow the throttle point), and (2) the variations in thickness,gangue, and mineralogy due to temperature, pressure, and salinity changes.Deposi- tion of copper, calcium, magnesium,and arsenic was apparentlynot affected by thechanges occurring in the orefluids. Gold solubilities, however, are greatlyaffected by thesevariations (Helgeson and Garrels, 1968), so thedeposition ofgold would decreaseafter the solutions have passedthe throttlepoint.

This model suggeststhat high gold values could continue eastward at depth,given continuation veinof structures. Silvervalues would probablyalso continue to the east attheir moderate to low values.

232 Additionalareas of high silver values are unlikelyeast of thepresent workingsand at depthin the system and will onlybe found in thoseareas that were abovethe throttle point (in the western part of themine').

ACKPumL-

The writers thank Teck Corporationfor financial support for this work. B. Goetting, B. Pergey, R. Verzoza,the staff at the Beaverdell operation, P. Christopher, and A. Sinclairhelped in thisstudy. Shen Kun, visitingscholar fromChina, did mch of theexcellent polished section andfluid inclusion work referredto in thispaper. J. Newlands did most of thedraughting.

REPEREXES

Christopher, P. A. (1975a) : Highland Bell (Beaverdell) Mine (82E/6E), B.C. Ministry of Energy,Mines 6 Pet, Res., Geo:Logy, 1975,pp. G30-G33...... (1975b) : Carmi-Beaverdell Area(82E/6, It), B.C. Ministly of Energy,Mines 6 Pet. Res., Geological E'ieldwo,ck, 1974,Paper 1975-1,pp. 27-31...... (1976) : Beaverdell Area (82E/6E), B.C. Ministry of Energy, Mines 6 Pet. Res., GeologicalFieldwork, 1975, Paper 1976-1, p. 15. Helgeson, H. C. andGarrels, R. M. (1968):Hydrothermal Transport and Depositionof Gold,Econ. Geol., Vol. 63, pp. 622-635. Kidd, D. F. and Perry, 0. S. (1958):Beaverdell Camp, B.C., inStructural Geology of Canadian Ore Deposits, Vol. 11, 6thc%mmmealth and MetallurgicalCongress, Canada, 1957, C.I.M., pp.136-141.

McKinstry, H. E. (1928) : SilverMineralization at Beaverdell, Ewitish Columbia,Econ. Geol., Vol. 23, pp. 434-441. Reinecke, L. (1915) : Ore Deposits of theEeaverdell Map Area, Geol. SUrV.r Canada, Mem. 79. 178 pp. Sinclair, A. 3. (1976) : Applications of Probability Graphs in Mineral Exploration, dssoc. Explor. Geochem., Special Vol. 4. Staples, A. B. andWarren, H. V. (1946a):Minerals from the Hiqhland- Bell Silver Mine, Beaverdell,British Columbia, LJnivers.ity of Toronto, Geol. Ser. 50,pp. 27-33. Staples, A. B. andWarren, H. V. (1946b):Mineralogy of the Ores of the Highland-Bell Mine, WesternMiner, Vol. 19, May, 1946,pp. 38-43 and June,1946, pp. 54-58. Thompson, M. andHowarth, R. J. (1978) : A New Approach to theEstimation of AnalyticalPrecision, Jour. Geochem. Expl.,Vol. 9, pp.23-30.

233 Watson, P. H. (1981) : Genesis andZoning of Silver-GoldVeins in the Beaverdell Area, South-CentralEzitish Columbia, MSc. thesis, University of BritishColumbia, 156 pp. Watson, P. H., Godwin, C. I., and Christopher, P. A. (1982):General Geologyand Genesis of Silver andGold Veins inthe Beaverdell Area, South-CentralBritish Columbia, Cdn. Jour. Earth Sci., Vol. 19, No. 6, pp. 1264-1274. White, W. H. (1949):Beaverdell, B.C.Ministry of Energy, Mines & Pet. Res., Ann. Rept., 1949, pp. 138-148.

234 Flgure 78. Regional geoiogl withlocations of majormines in theBeaverdeIimine area, southcentralEritlsh Columbia. bdlfledfrom binecke, 1915 andChristopher, 1972, 197%. and I976

235 2 36 N

i i

" i I l0bU I1 r b 2bod DISTANCE

I 1 I I I I

DISTANCE

Figure 80. %constructedpian and 'section' plot of the Lass vein system, Beaverdei I mine area. SI lver analyses are separated into background and anonalws populations as notedIn the legend.Long dashed linenarks the boundarybetween tho silver and gold-rich sections ot the mine, and short dashed lines indicate the divisionsfor calculations of four-waymans (see Fig. 85).

237 !

: "i; I

I I' I IOo0. 0 oh^ 2200' SdOO' DISTANCE

2dOO~ I DISTANCE

Figure 81. &constructedplan and 'section' plot of the Lass vein system, saverdell mine area.Gold analyses are separated into backgrwnd and anomlous populations asnoted in the legend. Long dashed line marks the boundarybetween the Sllver and gold-rich sections of the mine,and short dashed I ines indicate the divisionsfor calculations of four-h'aymans (see Fig. 85).

238 !

I 0, I I' 0 IObO~ DISTANCE

Pb I I I I I I I I A 1

0, I I I I) I 30100. Gm 0 10 00' ZdOO' DISTANCE

Figure 82. &constructedplans of the Lass vein system, Beaverdei i mile area. me hlghest 50 analyses for zlnc (top) and lead (bottom) are plotted uslng the foliwing: solid square, tirst IO; mild triangle, second 10; open square, third 10; open triangle,fourth 10; and open circle, fifth lo,

239 i

DISTANCE

N Au t I

Figure 83, Faconstructedplans of the Lass vein system.Beaverdell mlne area. Ihe hl@est 50 analyses for SIlver (top) and gold (bottom) are plotted using thefollwing: solld square, first 10; solidtriangle, second 10; open square, thlrd IO; open triangle,fourth IO; andopen clrcle,flfth 10.

240 8. 8. moo' 2000' 3000' DISTANCE

Figure 84. &constructedplan and 'section' plot of the Lass vein systern, baverdel I mine area. @Id (ppb)/SI lver (ppm) values are separatedinto two populatlons. above and below a ratlo of 5. Long dashed llne marks thebomdary betweten 51 lver and goid-rich sections of the mine.

241 I -,

Figure 85. Plot of arithmetic means and standard errors of the mean for gold,silver, lead. and zinc, after division of the Lass vein systeq Beaverdell area, into two andfour sections (see Figs. 81 to 84). Left-handside of the plot Is uppermst,western section of the vein system; the right-hand side is dwn dlp, deepest. and easternnost section of the mlne. Distance is measured along the reconstructed plane of the vein.

242 WEST END OF LASS VEIN ' SYSTEM

,-," -1- - \\\\ \\ B DEPTH ~,=90-450m

g Ag:29lppm Au:764ppb .<

Figure 86. hbdeiof the Lass vein system, baverdell area. The vein 15 dividedinto an upper, siIver-rich part and a larer, goibrlch part. Averagevalues for key elementsand vein thicknesses are noted on the model. Mineralization stages and tenperature and depth (PH = hydrostatic pressure, PL = lithostatic pl-essure) estimates are from fluid inclusion studies (Watson, 1981).

243 244 ...... 0~~~00wc~~~0wwwwcm~m~n~oo0m~ooo-ow~om~0~00~~moomo~m~1m m-

24 5 ...... 0mg~w~~~~~mu0~~mmm~omu-~~0~~wm0owo000moo~omu~om~~oom-

0000000000000000000000000000000000000000000000000000 ...... dN~~~~0~0cmw0w~~00~-~mwmw-mom~o~~m~~~omcom~~-m~-~~~~~ mmwouw o wwm ~mmwm~w~m~~~ummw~~m~-~mo~-m-o~~wmo~ w-- mm~NW"~ ~m-9wm---o-~c O-~WOON~UCT-J-N~C z:o;" NU m " N vm 9 - CON - m-cgmm - N N

...... m~C-m9Cffl99fw-ofONmNO-~~c-N-wO-O-COwffl-oww~~~~~-mco~~c ~u~~~w~wm~mm~w~mwm~mommc~mwm-om~w~mw~m-ommowc~~~o--u OONfflNN m u nm-w~~W-N--C NWN - NC wg NN u-~qm-mm -- N - -N

246 247 TABLE 2. Means and StandardDeviations Determined Graphicallyfor 1 Partitioned Element Populationsin Granodiorite-Hosted Vein Vein Material'in the Lass Vein System, Waverdell Mine Area, South-CentralBritish Columbia

Element Population A 3 ~opulations3B, FJ'

b b+s% b b- s % b b+s b-s

55 3.76 9.12 1.40 45 0.38 45Zn 1.40 % 9.12 3.76 55 1.40 0.11

Cdppm 457 55 1288 17843 45 2 34 10

Cuppm 513 70 1202 19576 30 126 45

Sb ppm 10 1318 2138 794 90 79 162 38

Pb % 3.00 38 4.30 2.09 37 0.54 1.02 0.29 25 0.12 0.35 0.050.35 0.12 25

6 0 8.99 13.49 5.94 40 3.72 6.84 2.206.84 3.72 Fe 40 %5.94 13.49 8.99 60

Ag ppm 26967 457 427 18 105 174 68 15 34 135 8

Au2239 ppb 646 90 191 1051 15 4

72 1.20 1.70 0.86 28 0.13 0.24 0.070.24 0.13 28As 0.86 % 1.70 1.20 72

30 5012 10233 2570 70 1202 2291 6172291 1202 70 2570ppm 10233 5012 30

Mg0.14 % 0.45 0.25 70 30 0.08 0.050.12

Hg ppb 124 100 20 3 100 1143 14962 87

100 1.75 9.90 0.31

1. Partitidnedinto populations on logarithmicprobability plots, using the procedures of Sinclair (1976). 2. Thereare 209 samples inthis group. 3. b is antilog OF rean cf logtransformeddata; b+s is antilog of mean plus onestandard deviation of logtransformeddata; b-s is antilog of mean minus onestandard deviation of logtransformed data. 4.24% of the Co values were below the analytical detection limit.

248 ..... -ooo:,

ofomowmm-Y) OWON N-NNU OuNr.8uw--m 0-00000-00..... -000+?0~00

..... -0000+~oo~o

OY) om ON ?Y -?

249 REVELSTOKE t 0 40 MI LES 0 60

\ CANADA U.S.A.

Flyre 87. Generalizedlocations of AlnSwOrth,Slocan City, Slocan,and Trout Lake rnlnlng canps,southeastern British Colurnbla.

250 SPATIAL DENSITYOF SILVBR-LEAD-ZINC-GOLD VEIN DWMITS IN POUR HIPING CAlQS IN SOUTHEASTERN BRITISH COLUUBIA (BZF)

By 1. B. Goldsmith and A. J. Sinclair Departmentof Geological Sciences, University of Briti:;h Columbia

INTRODOCTI(MI

Spatialdensity appears to have several practical applica.tions important in resource assessment, viz .:

(1) defining limits to miningcamps, (2) providing a systematicbasis for comparing mining camps in terms of averagedeposit density OK averagemetal concentration, and (3) recognition of systematicvariations in spatialdensity of mineral occurrenceswithin individual mining camps.

Here we examinethe potential uses of spatial density applied to clusters of veindeposits.

Sinclair(1979) suggested that contoured spatial density maps of location data(centroids) of mineral depositsmight provide a consistentif empirical meansof definingboundaries to certaintypes of mining camps or mineralized centres. In particular, herecommended that a moving average method beused as a basisfor contouring 'number of veinsper squarekilometre' and that the 0.5 densitycontour beused todefine the empirical limits tothe Rinsworth vein camp in southeasternBritish Columbia. lhe method appearsapplicable to two-dimensional problems and, of course,suffers the limitation that the 0.5 spatialdensity contour does not exist as a real entity. Exact locations of some deposits are notalways readily attainable from available literature but this problem is restrictedlargely to small deposits actively explored and/or exploi- tedduring the nineteenth century. Uncertain locations in generaldo not appearto represent problems in contouring spatial density because the uncertainty is generallysmall relative to thescale ofa mining camp.

Thisstudy extends the early work by Sinclair(1979) toinclude four vein camps,Ainsworth, Slocan, Slocan City, and Lardeau(Trout Lake), in southeasternBritish Columbia (Fig. 87) in anattempt to generalizo the approach in relationtovein camps.The database for three of the mining camps is an updatedversion ofa computer-basedproducer file established by Orr and Sinclair(1971). Data for the Lardeau (Trout Lake) camp are an editedversion of a fileestablished originally by P. B. Read (Read,1976; Goldsmith, et dl., in preparation). The former file(Slocan, Slocan City, andAinsworth) contains information onlf for

251 TABLE 1

AREA MF,ASURENENT STATISTICS, AlllSWORTLI llINIllG CAMP

25XOVERLAF

4hx 81 78.0071.70 71.86 201.67 81 63.8463.66 63.83 165.31 11 .88 77.8811.88 63.0163.96 Zhx zkm 80 36.3663.54 36.35 91.13 80 21.9628.26 12.13 28.08 36.10 36.3036.10 28.08 28.02 lkm x lh 12 13.0013.68 13.14 15.58 11 10.80 10.80 10.00 21.97 13 .68 13.8013.68 10.80 10.80

50% OVERLAP

0.5 DEPOSIT~CELL 1.0 UEPOSITICELL

4hX176.5068.154h 68.28 68.10 81 81 56.2256.22 56.1.8 145.49 67.98 56.28 55.98 56.28 67.98 1 2hX 2h 1 15 I 30.36 !::::I 30.30 I 78.48 11 15 60.181 23.2423.22 23.28

l5X OVERLAP

I 0.5 DEPOSITICFLL 1.0 DEP0SITiCEl.L 212.24 61.26 67.20 63.68 19.56 19.08 30.42 9.45 9.36

rAOLE 2

REA MEASUREMENT STATISTICS, SLOCAN llINING CN4P

25% OVERLAP

0.5 UEPOSITICELL 1.0 DEPOSIT/CELL, WindOv U A" A" Number of Miles2 Au A" measurements) Miles2 km2 Deposits (4 mearurementr) Miles2 kt72

4km x 4km I 176I160.50 160.98 I 140.46140.04140.36 363.51 160.32 160.32 140.52140.40 108.00 107.46 189.3573.1173.2013.14 107.64 107.58107.64 73.08 73.02 28.65 28.47 52.8420.4020.43 20.31 28.53 28.65 20.4320.37 50% OVERLAP ! I I 0.5 DEPOSITICELL II I 1.0 DEPOSlT/CElL 4kn x 157.084km 176 156.78156.59 405.56 137.40 175 137.76131.15 356.16 156.24 156.24 137.40 138.42 2km x 102.122kn 176 102.36102.03 264.26 72.18 172 72.0672.11186.75 102.18 101.46 72.12 12.06 lkm 30.60x lkm 124 79.0230.5130.42 19.10 121 19.5019.4650.39 30.60 30.42 19.50 19.32

75% OvEnLhr

Okn x 4km 175 409.2s138.54139.2ti 158.0~ 158.1n 158.1ti359.36 176 138.75 1 51.74 158.10151.74 138.18139.02 2km x Zkm 171 90.0090.42 9n.00 233.1 165 54.6654.78 54.74 141.16 89.94 89.6489.94 54.66 54.8'1 lkm x lkln 101 211.10 20.10 20.19 52.7'1 99 11.18 15.18 15.33 39.11 20.10 20.4620.10 15.4815.18

252 depositswith a recordedproduction of atleast one sh'xt ton oE ore. The filefor Trout Lake camp containslocations of allpublicly recorded depositsirrespective of whetheror not they have produced ore.

MEl'HOL)OUXY

Considerthe problem of depicting spatial density of minc?ral occurrences to betwo-dimensional. An interpolationtechnique is requiredto provide spatialdensity estimates on a regulargrid superimposed upona district containing numerous irregularlylocated occurrences and/o:c deposits. The spatialdensity values for each cell of the gridthen can be contoured by simplelinear interpolation,either by hand or machine. One procedure usedhere is to move a (square) window over thefield of interes-tin a regular,periodic fashion, count the number ofdeposits i.n the window at eachposition, and assigneach count to the centre of the square for which thecount was obtained.

Threeparameters can be varied in thisprocedure: (1) the window shape, (2) the window area, and (3) theproportion ofoverlap (if any) of adjoiningcounting cells.

The level of variability in spatialdensity data that results from these sources mst be quantified if spatial density is to beused in a meaning- fulfashion.

MWURPWENT OF SPATIAL DENSITY VARIABILITY

We haveattempted to evaluate several sources of variability in obtaining spatialdensity estimates for vein mining camps. In particular, we have examined the effectsof:

(1) varying size of counting window, that is, 1 by 1 kilometre, 2 by 2 kilometres, and 4 by 4 kilometres, (2) defining camp area by two differentspatial density contours, that is, 0.5 depositper cell and 1 .O depositper cell, and (3) iestingactual reproducibility of camp areaestimate:; by planimeter.

Datafrom our tests forthree mining camps are summarized in Tables 1, 2, and 3 fromwhich severalconclusions seem evident. The mostobvious feature of thetabulated data is thatplanimetric measurements in camp areasvary mch less than 1 percent of the area;these errors are negligible.

Estimated camp areasincrease dramatically as the size of thecollnting cellincreases, regardless of extent of overlap.This results 1,argely from an ever-increasingzone of no depositsthat is includedwithin the camp boundariesas the cell size increases. lhis effectcan beminimized

253 25% OVLRLAF

0.5 1.0 OEPOSIT/CTlI. Window OEFOSITICELL Size Number of Miles2 Au AV N".i.er of hliler2 AV Av Deporifr (6 meriuremfnti) nliles' kmz Deposits (4 merrurements) Ililer2 km2

akn x 4km 60 111.90 111.30 111.60 289.04 SB 82.20 81.95 82.165 212.81 lil.3U 111.90 82.32 82.20 Zkm x 2km 57 46.62 46.68 4S.GR 120.90 Si 39.00 39.18 38.05 101.13 46.74 46.68 39.00 39.00 ikm x 1km 57 10.SO 19.16 19.55 50.62 37 6.8.1 6.84 6.84 17.72 19.50 "_ 19.62 6.84 6.84 50% OYERLAP

0.5 DIPOSITICTI.I 1.0 DEPOSITICELI.

4x1" x Oh 59 89.52 80.52 R'l.48 231.74 19 17.94 77.70 77.78 201.44 88.45 89.40 77.88 77.58 2kn x 2km 57 44.44 41.18 45.07 116.74 55 37.56 37.20 17.43 96.93 ds.06 41.12 37.50 37.44 ikm x lkm 57 20.34 20.16 20.2R 52.53 50 10.17 10.18 10.11 27.18 20.16 20.66 10.17 10.16

75% 0VCllLAY

0.5 owoslr/cCLt 1.0 DmnslrmLI.

4km x 4km 59 61.74 62.10 62.07 160.76 62.10 62.3462.10 50.9451.18 2km x 2krn 57 43.0042.78 42.87 III.OZ 42.90 42.78 34.38 34.50 lkm x 1km 57 11.16 17.40 17.28 44.75 43 17.16 17..10 7.26 7.26

by using a 1.0 ratherthan a 0.5 deposit-per-cell contour. Nevertheless, window size is a largesource of variability in mining camp areas by the method we outline. To counteract this problem we define a mining camp somewhat subjectively on thebasis of thesmallest window sizethat results in a highproportion (more than 90 per cent) of known occurrences beingcontained within a referencecontour (for example, 0.5 depositper cell).

Extent of overlap of adjoiningcounting windows doesnot appear to be an importantsource of variabilityfor smallest cell sizesthat produce a cohesiverather than a disaggregatedoutline. For example, for Slocan camp the 2 by 2-kilometre window producesareas of 121, 117, and 111 squarekilometres for overlaps of 25, 50, and 75 percent respectively.

Our subjectiveevaluation of thesedata and the many maps that we viewed (onefor each line of information in eachtable) have led us toconclude thatareas of mining campscan be definedusefully andreproducibly, if empirically and subjectively,as follows:

(1) use a 0.5 depositper cell asthe margin contour to define the outer extremityof a mining camp, (2) use 50 percent overlap ofsquare counting cells, and (3) cell size mustbe selected by trial and errorto be that smallest size which retainsthe large majority of deposits ofa subjectively recognizedmining camp withinthe marginal contour,

254 WAlPLEs OF SPATIAL DmSITY MAPS

TWO extremecases of the application of spatialdensity procedures appliedto mineral deposit location data are: to define boundari,es of clusters of vein deposits, and to examine patterns of spatialdensity contours of mineral deposits within a mining camp.

OUTLINIWG UININGCAWS

In a largeregion containing several mining camps we might wish to develop a reproducibleprocedure by which we candefine boundaries to mining camps and determine anestimate of their individualgeographic limits. Such information wouldbe usefulfor purposes of quantifying the distribution ofmineral occurrences in a camp in terms ofaverage spatial density.Similarly the amount of variousmetals concentrated into veins per unitarea in a mining camp could be examinedand displayed.

The foregoingobjectives require that we know the total numberof deposits in a camp andthe geographic limits of the camp. Of course a newlyfound deposit in anold camp or one outsidethe existing camp limits will bias the parameter we areestimating. As long as we recognizethese sources of errors,they need not represent serious problems,and, in fact,are likely minimal in manycold, thoroughly explored camps.

Figure 88 is a moving averagespatial density contour rmp for an area includingthe northern end of the Nelsonbatholith. A window of :2 by 2 kilometres was usedwith 50 per centoverlap in the two principalgrid directions. NOte that in such a case a singledeposit wi:t1 occur in four cells whose centresare in a squarewith sides half the cell dimension. The 0.5 depositper 4-square-kilometre contour around an :isolateddeposit is therefore the same sizeas the basic counting cell. In fewa cases where deposit locations are exactly on the boundary of a counting cell, isolateddeposits are surrounded by a rectangularcontour with area less than the basiccell area. After some experimentationthe artificial contour 0.5 deposit per 4-square-kilometres was selectedarbitrarily as setting the outer limit of veinconcentrations defining mining camps in the area.

Once anacceptable limit is definedfor a mining camp we can calculate averagespatial density andaverage known metal endowment. Our present study is concernedprimarily with spatial density of mjneraldeposits, althoughthe methodology can be extended easily to the presentationof metal endowment using known metalproduction. Average spatial densities are summarized in Table 4 forSlocan, Slocan City, and Ainsworth mining camps. It is important to realizethat the figures quoted in Table 4 are derivedonly from thosedeposits lying within the 0.5 depositper 4- square-kilometrecontour.

25 5 256 9 257

The data of mble 4 arebased on the same countingcriteria for the entirearea. Such a procedure is probablydesirable for reasons or practicability. However, differentcounting criteria may be optimalfor different camps.Cur experiencehas shown thatcounting cell size is particularlycritical (see Tables 1, 2, and 3) to camp area estimates. A subjectiveevaluation ofthe Ainsworth camp, a ti.ghtly clusteredgroup of veins in a relativelysmall area, suggests that a 1 by 1-kilometrecounting cell is more appropriatethan the 2 by 2-kilometre counting cellused for Figure 88. Spatial contoursusing a 1 by 1- kilometre counting cell forthe equivalent area of Figure 88 are shown on Figure 89. Thislatter plot also demonstrates how disaggregated a camp appears if toosmall a counting cell is used as in the case ofSlocan and SlocanCity camps.

TAKE 4. AVERPGE SPATIAL DENSITIES FOR SINE SOUTHEASTERN BRITISH COLlMBlA MINING CAWS (BASED ON 2 x 2 km COUNTINGCELLS WITH 50 PERCENT OVERLAP)

Camp Area No. of Deposits (km') Depositsper km2

Alnsworth 78.5 Alnsworth 71 1.0 ocan 264.3 SI ocan 172 0.7 Siocan City 116.7 59 0.5

SYSmTIC VARIATIONS IN SPATIALDmSITIES

Spatialdensity maps ofmining camps alsoare important as a meansof examiningsystematic patterns to depositclustering within individual mining camps.For such a purpose we arefaced with the same problem as in defining camp boundaries,that of selecting an appropriatecontouring cell (window) size.If a cell is toosmall, many irregularities in .the contours and 'holes' may obscure general trends. A practical means of selectingan appropriate contouring approach for examining variations in spatialdensity in a camp is to use a square cell withsides approximately theinverse of thedeposit densities ofTable 4. %us,Ainsworth camp canbe examined with a 1 by I-kilometrecounting window, Slocan City cawwith a 2 by 2-kilometrecounting window,and Slocan City imidway betweenthe two. Four separate mining camps aredescribed in detail.

AINSWORTH CAMP

Spatialdensities for Ainsworth camp (Sinclair,1979) are shown on 'Figure 90. Here it is apparentthat the cam is well defined as a cohesiveunit with only a singlenearby outlier, yet local concentrations are apparent withinthe camp. It is apparentthat a singlecontwring grid will serve

259 bothpurposes, that is, definegeneral camp limits andaverage spatial densities,as well as showing local structureto the spatial densities. Average spatial densities calculated in this case for a squarecontouring grid cell of l'by 1 kilometreprovide an average density of 0.48 deposits per-square-kilometre. This compareswith anaverage density of 1.05 depositsper-square-kilometre grid determined in an earlier section, and providesanindication of thevariability of mean spatialdensity estimatesrelative to size of contouring grid. As expected,the smaller thegrid, the smaller the 'camp area'and, if number ofdeposits remains constant,the higher will bethe average spatial density.

Inthis particular case it appearsthat choosing the smallest contouring cellthat provides a cohesive camp outline is the optimalempirical approach.Such a procedure,although subjective, provides potential for reproducibility by different operators.

It is interestingto speculate about the importance of thefive highs shown in thedetailed spatial density contours for Ainsworth camp. A plot of thefive largest deposits in the camp shows thatall are within thefour southernmost spatial density highs. Even withoutfurther informationone might speculate that the northernmost high, that consists only of smalldeposits, is an areathat warrants investigation. The writers' interpretationfor the camp is that'bedded' veins represent syngeneticdeposition in Cambrian time and that some ofthese bodies were partlymobilized during and/or after emplacement of the Nelson batholith to formnumerous small 'transverse'veins. lhis model is consistentwith observeddistribution patterns ofsmall (mostly transverse) deposits, relativeto large (mostly bedded) deposits. It provides some geological basisfor conducting further exploration in the northern spatial density high.

SLOCAN CITY CAMP

Visualexamination of the distribution of deposits in Slocan City camp shows that the distribution is asymmetric with a small area of relatively highdensity and a much largerarea mainly to the east, of much lower density(Fig. 88). A gridserving for one part may notserve for the other. However,a gridsize controlled by theless dense area will serve,generally at least, forthe denser areas. The contoured results ofFigure 88 for Slocan City camp based ona 2 by 2-kilometrecontouring grid cell cannotbe improved significantly by theuse of a smallercell size. High spatialdensities form a horseshoe-shapedzone with low valuesboth in the core and surrounding the 'horseshoe.' Bnsidering the 'structural'nature of the camp and known zonalpatterns, the 'horseshoe' probablyreflects a fundamentalattribute of the camp. Forexample, near-circularfracture patterns on thisscale (approximately 4 kilometres diameter)might beproduced during emplacement of an underlying hypabyssalintrusion. If such is thecase, the 'opening' in thehorseshoe may representan area of explorationinterest because a circularpattern could be expected.

260 SLOCAN CAW

In Slocan camp it is advantageous to examine spatialdensities at two differentscales of contouringgrids. A largecontoctring grid. cell defines a simpledensity high along a north-northwest:direction and allowsfor clear definition of the camp. However, the camp contains a verylarge number of deposits and the possibility of d,etermining some detailedstructure tospatial densities exists. An example shown on Figure 91 is based ona counting window cell size of 1 by 1 kilometreand shows clearlyseparate groups or clusters of pastproducers. As in other examples, a considerablesubjectivity exists inattempthg to interpret thespatial density patterns.

TROUT LAKE CAMP

TroutIake camp represents somewhat differentdata than do the other three camps consideredto this point. Only a smallpoxtion of the 180 depositsreported in the camp haveproduced. Instead cont:ouringof spatialdensities of pastproducers, we havecontoured spatial densities of allrecorded veins andcompared the positions of 45 known producers withthe resulting pattern. The results,based on a contouringgri.d cell of 2 by 2 kilometres,are shownon Figure 92. Clearly,several separate major clusters of deposits are evident.Within each of these cl.usters are well-definedhighs. Plotted positions of producers lie within the highcontours. As with the Ainsworth camp, exp:tanationan is not obvious,particularly since here we do notappear to have the possibility of two separategenetic models. Furthermore, there is the poss:tbility thatintense exploration in the immediate vicinity ofa largedeposit will give rise to more small discoveries.In other mcds, the association of past producerswith areas of highspatial densities io self- generating. This latterexplanation may betrue in part, but it doesnot appeartoprovide a totalexplanation in old camps that havebeen thoroughlyexplored over a period of 70 or 80 years.

Spatialdensity contours clearly define three separate clusters of camps withinthe Trout Lake area. These separateclusters represent a quantif- cation of previouslyrecognized mineral belts.

Becauseof the very narrowwidths of themineral belts ]relative to their lengths, it is notpossible to see any structure in the spatialdensity contoursapart from theassociation of pastproducers with spatial densityhighs.

DISCUSSION

Spatialdensities of mineraldeposits offer problems relating to basic data and interpretation. One problem is illustrated by a major lode alongwhich several different deposits are known -- at w!>at pointdoes an oreshoot along a lode become a separateentity for contouringpurposes?

261 0 0 * m v) v) I I

C C U

C a 'c

C U d

C b d 0 m v)

262 263 We haveignored thisquestion by acceptingindividual mining properties as individualdeposits. Conversely, two separateveins from a single property may have theirproduction data combined in which case spatial densitycontours will produce an overlysmoothed pattern.

Newly founddeposits affect spatial density contours derived from a data baseof known deposits. Of course,spatial densities become under- estimatesif new depositsare found within the borders of a camp. It is possiblethat new deposits will befound outside the marginsof a camp andadd tothe area of a camp. Inthis latter case it is unlikelythat average spatial densities will changegreatly. Overall, spatial densities are biased on the low side of reality. In longestablished camps that haveundergone exploration for many decades,such as are studiedhere, thisbias is likelyto be slight in terms of mineraloccurrences but could be substantial,at least locally, to metal distributioncontours.

Average metal endowmentsof severalmining camps canbe compared. For example,average silver endowment inSlocan City camp, based on known production and the camp limits shownon Figure 88, is about 1 325 000 grams silver per squarekilometre. The comparablefigure for Ainsworth camp, based on the camp limits of Figure 90, is about 2 457 000 grams per squarekilometre. me use of metal spatialdensity contours appears a practical means of generalizingresource (metal) productivity in mining camps wherepro- ductionand/or resources are notconcentrated in a few deposits. Even where many deposits exist, metal productivitycan change dramatically overshort distances andlogarithmic values for contours are desirable. Most deposits were foundover a few yearsin the early history of the camps consideredhere. Modern explorationconcepts and methods applied tothese camps havenot yet resulted in a markedimprovement (increase) inthe number of finds, as might be expected if existingspatial densities are highlybiased. This is an interestingconclusion to emerge from an evaluation of spatialdensity maps,and some indication ofthe importanceof rates ofdiscovery becomes apparent,as does the need to evaluaterecent or new discoveries in thelight of their positions relative to known spatial densities.

CONCLUSIONS

(1) Average spatialdensities of depositlocation and metal endowment data,although biased, represent useful means ofcomparing vein camps. (2) In some cases spatial densities have internal patternsthat may provide some insightto specific small areaswarranting additional explorationor in providing an additional framework forconceptual modelsof mineralization.

264 In many casesthe large, valuable deposits in a vein camp occurin clusterswith many small deposits. It appearsthat: these associations may arisethrough complicated genetic historks, such as early formeddeposits being mobilized toproduce younger deposits. In othercases the clustering oflarge deposits with many smallerones may be purely a question of clusters of structures,all mineralized at more or less the same time. The suggestionthat spatial densities are highlyhiased seems un- reasonable in the camps examinedhere. The implication o:E this statement is that relatively few veins remain to befound within the camps themselves.

This work hasdeveloped intermittently over several years with the financial assistance of the GeologicalSurvey of Canada,the B.C. Ministry of Energy,Mines and Petroleum Resources, and the Science Council of EVitish Columbia. The technical assistance ofAsger Bentzen inproducing large -numbers of contoured spatial density maps is appreciated. Goldsmith, L. B., Sinclair, A. J., andRead, P. 8. (inpreparation.): An EvaluationofAverage Grades and Production Tonnaqes, Trout Lake Mining Area, SouthernBritish Columbia. Orr, J.F.W. and Sinclair, A. J. (1971): A Computer-Processable File for Mineral Deposits in theSlocan and SlocanCity Areas of Etxitish Columbia, Western Miner, Vol. 44, pp. 22-34. Read, P. B. (1976) : LardeauWest-Half, Geol. Surv., Canada, open File Rept. 464. Sinclair, A. J. (1979) : PreliminaryEvaluation of Summary Production Statistics andLocation Data for Vein Deposits, Sl.ocan, Ainsworth andSlocan City Camps, SouthernBritish Columbia, in Current Research,Pt. B, Geol.Surv., Canada, Paper 79-1E1, pp.173-178.

26 5 o, c 5 c 0 L ca I I I a 0<3 ,>>>'

266 G-IS OF WAGllATIC HAGNEl'ITB-WATITELODES, IRON MASK BATHOLITH, SOUTii-CENTRAL mITISH COLWBIA (921)

By R. U. Cann 3,313 Highland Way, Port Moody and c. I. Godwin Departmentof Geological Sciences, The Universityof British Columbia

INTRODUCTION

A worldwideassociation is known toexist betweentabular to 1ent.icular bodiesof magnetite-apatite and alkalicrocks occuring i,n a volcanicor subvolcanicenvironment. Major examples include: (1) Park's(1972) briefdescriptions of theoccurrences of magnetite-apatitebodies in Chile, Peru, Mexico, California,Philippine Islands, and Australia; (2) Geijer's(1931, 1960) descriptions of the famous apatit.eiron ores of Kiruna, Sweden; (3) KisvarsanyiandProctor's (1967) work on iron deposits in southwestMissouri; and (4) Kolker's(1982) review of iron- titaniumoxide and apatitelocalities in Virginia, New York, plebec, Norway,and Sweden.

Magnetite-apatitebodies associated with Precambrian alkalic rocks in Canadahave been noted in the Great Bear batholith,Northwest Territories (Badhamand Wrton,1976). In British Columbia similar lodesoccur in Mesozoicrocks at GaloreCreek porphyry copper deposit, northw,estern British Columbia(Davis, 1962), and in the Copper Mountain intrusionnear theIngerbelle porphyry copper deposit in south-central British Columbia. Thisstudy is concernedwith magnetite-apatite lodes in the Iron Mask batholith.

GEOLOGICAL SIWIIHG

The Iron Mask batholithlies in a northerlytrending belt Upperof Triassicvolcanic rocks known asthe Nicola Group (Fig.93), which range in compositionfrombasalt trachyte-dacite to (Northcote, 1975; Cockfield, 1948; Preto,1977). Argillite, limestone, and conglomerate havealso been noted within the group in otherareas (Cockfield, 1948; McMillan,1978; Schau, 1970). To thenorth the batholith is overlain by EarlyTertiary volcanic and sedimentary rocks.

Two major plutons form the Iron Mask batholith(Fig. 93). The larger one, the Iron Mask pluton,consists of a numberof successivelyemplaced, differentiated units, whereas the smaller, more northerlyCherry Creek plutonconsists of onlythe youngest unit. Figure 94 sholas thenorthwest

267 . 0 1 2 kilometres 0- 0.5 1 miles Nicola volcanics < Magnetite-Apatite dyke (dipping) a Cherry Creek unit; Breccia PERCENT DISSEMINATED MAGNETITE ml Pothook diorite wdlronmask hybrid

Figre 94. Slnpilfiedgeolog (after Northcote, 1977a) sharing abundance of disseminated mqlnetiteand dlstrlbutlon of magnetite-epatite dykes in Fbthook (diorite) and CherryCreek unlts. bta on magnetite are from this studyand Mathws (1941).

268 end of theIron Mask pluton, where relationships among several of the majorrock units andmagnetite-apatite lodes can be oblserved.These unitsaredescribed below,with emphasis on associatedmagnetite mineralization.Subdivision of the units in the Iron Mask plutonfollows descriptions by Northcote(1975, 1977a, 1977b).

Picrite occursas small, fault-bounded,lenticular bodies. (too small to show on Figs.93and 94) of serpentinizedbasaltic rod:. Picrite is commonly associatedwith copper prospects (Carr, 1956; Qrr andReed, 1976).Chromium-rich magnetite occurs asfine anhedral grains in the matrixand as grains along fractures in serpentinized ol.ivine. Volume content ofmagnetite is generallyhigh, but varies from trace amounts to 15 percent.

Iron Mask hybrid unit is agmatitic, consisting ofangular androunded mafic fragments in a dioritic matrix. Magnetite andcopper sulphides are common inthis unit. Onlyone sample of theunit, cont,lining about 10 volume percent magnetite, was taken for minor eleme~lt analysis of magnetite.

Pothook dioriteunit, gradational in compositionbetween Iron Mask hybrid andCherry Creek 'syenite', is medium tocoarse grained, 1.ocally displays cumulate textures, and is maficrich. Magnetite content averages about 10 per cent andoccurs as interstitial grains. Most known magnatite- apatitelodes and also a number of smallcopper showings which are commonly associatedwith breccia occur within the unit (Fig. 94).

Sugarloafunit (Preto, 1968), not known withinthe area cbf Figure 94, is a dioritecontaining hornblende and feldsparphenocrysts and onlytrace magnetite. Copper mineralization is common inthis unit.

CherryCreek 'syenite' (Preto, 1968) is a porphyriticunit rangi.ng in conposition from diorite to syenite. A monzoniteconposition is the most atundant.Subhedral magnetite grains,about 5 per cent by volume, occur eitherinterstial to, or within, mafic minerals. Irregular bodies of intrusionbreccia are common alongthe northern margin c8f theIro~n Mask plutonand host porphyry-type copper mineralization. The Aftoncopper deposit(Fig. 94; Qrr andReed, 1976) is the mostimportant porphyry depositin the Iron Mask batholith and is locatedonly 1.25 kilometres northwestof the largest magnetite-apatite lodes, which are known as the Magnetshowings (Fig. 94).

Magnetiteatundance in thepreviously mentioned units are shown schematically on Figure 94. A discordantdecrease in magnetite alxndance between the Pothook diorite and theCherry Creek 'syenite' is evident :in the diagram andfrom data in Table 1. A correspondingincrease in apatite betweenPothook and Cherry Creek units(Table 1) hasalrio been noted by Mathews (1941).

269 FORM AND DISTRIBUTION

Most magnetitelodes (Cann, 1978) occur as steeply dipping tabular bodies withsharply defined walls that vary in widthfrom less than 1 centimetre to 3 metres at the Magnetshowing (Fig. 94) and 6 metres at the GlenIron mine.Although lodes are generally steeply dipping, some dipas little as 40 degrees south (for example, Eloose showing, Fig. 94). The lodes tendto split at irregular intervals andend abruptly. No singlelode hasbeen followed for more than 200 metres, in partbecause of limited outcrop.

Magnetitelodes are concentrated at the northwest end of the batholith. Along thenorthwestern margin of the Iron Mask pluton and atthe Glen Iron mine,most lodestrend easterly; however,those at the Magnetand Iron Cap trendnorthwesterly. They are interpreted to be dykes.

MINERALOGY AND TEXTURES

TheMagnet showing was studied inthe most detailbecause exposures are excellent. Lodes at the Magnet showing consistpredominantly ofmassive magnetitethat contains white or pale pink euhedral apatite crystals up to 3 centimetreslong, and prismaticamphibole crystals up to 6 centimetreslong. Amphibole and apatite crystals frequently occur in layers adjacent tothe walls of the lodes. Long axes are perpendicularto the walls of thelodes; textures are spinifex-like andmight result from quenching at themargin ofthe dyke. Polished sections ofmassive magnetite show aneuhedral or subhedral granular texture, with individual grainsranging from 0.1 to 0.5 millimetre in diameter.Trains of spinel inclusions less than 30 microns in diameterparallel some grain boundaries. When etchedwith bromic acid, one sample displayedan extremelyfine crystallo-graphic exsolution texture of ilmenite in magnetite.

Adjacenttothe main dykes,numerous subparallel dykelets are often alndant enough to form a crisscrossingnetwork; most are less than 5

270 centimetres wide. Some dykesintermediateof width (1 I) to 15 centimetres)are breccias containing numerous angular to subroundedinclusions ofhost rock. Dykelets are commonly enclosed by a 1 toZ-~nillimetre-wide pinkalbitized envelope, andoccasionally contain narrowe.pidote cores.

At the Magnet showing pyrite and chalcopyriteoccur in veinsalong fractures in magnetite-apatite dykes,indicating that sulphide mineralization is post-magnetite. Ingeneral, magnetite,-apatite bodies at Aftonare sulphide poor, probably because they contain few fractxres. Late-stageveins of drusycalcite crosscut magnetite andsulphide mineralization.

MINOR AUD MAJOR EL- IN MAGNETITE J?RM IROW IUSK BATHOLITH

Characterizations of magnetite from theIron Mask batholith havebeen done on overallcomposition based on majorand minor oxides as determined by electronmicroprobe and in terms of minorelement content alone as determined by atomicabsorption. For conparative purposes magnetite samples havebeen grouped by form (disseminatedor massive) and host rock (syenite,diorite, picrite). Syenite as used in thisstudy is equivalent tothe CherryCreek unit, which includessyenite, monzonite, and diorite. Diorite is equivalentto the Pothookand Iron Mask hybrid units (Fig. 94). Samples weregrouped on thebasis ofpetrographic analysis, mapping by Northcote(1977a. 1977b1, and examination ofsamples by Northcote (personalcommunication, 1977).

Liberation ofmagnetite was achieved by passing all sanplesof massive anddisseminated magnetite through a jawand conecrusher, follohed by pulverizationbetween ceramic plates until the sample passedthrough a 100-mesh nylon sieve.Massive magnetite with little gan,pe was readily concentrated using a repeatedcycle of underwater magnetic separation and grinding by hand withceramic mortar and pestle until the desired purity of greaterthan 95 volume per cent magnetite was obtained.Magnetite disseminatedinintrusive rocks and massivemagnetite with alxindant ganguerequired initial rough separation with an Eciez Wet Drum Magnetic Separatorand density separation in bromoform beforeusing the method described previously.

plantitativeanalysis magnetiteof €orcobalt, chromium,copper, manganese,magnesium, nickel,lead, titanium, vanadium, arid zinc was done by atomicabsorption spectrophotometry. A Varion-Techtron A?+-4 unit was usedfor chromium, copper, magnesium,manganese, vanadium, and zinc analysis, and a Perkin-Elmermodel 303 unitwith background correction (Fletcher,1970) was useddetermineto cobalt, nickel, andlead.

271 272 Titanium was determined at a commercial facility, Min-En Laboratories, NorthVancouver. Sample digestion and analytical methods were similar to those of Nakagawa (1975),except that inthis study (calcium was not removedfrom solutions prior to analysis.

Microprobeanalyses were done on an ARL-SEMQ instrument (Cann, 1979). Background,deadtime, absorption, atomic number, arid fluorescence corrections were appliedusing a computerprogram developed by Fucklidge and Gasparrini ( 1969).

CWPOSITION OF MAGNETITE SAMPLES PROM IRON I(ASK BATHOLITH

Compositions of 13 disseminatedand massive magnetite samples: were determinedusing the electron microprobe. Results of t.he analyses are displayedinTable 2 and plotted on Figure 95. A minimum of three magnetitegrains per sample were analysed.For purposes; of determining averageconpositions, only analyses with totals exceed:tng 97pe.r cent were considered.Molecular per cent ulvospinel was calculatedbased on themeasured titanium content.

Cr203+Ti02 DISSEMINATED

0 Syenite host

A Diorite host 0 .Picrite host MASSIVE Syenite host

A Diorite host

FeO Fe203

Flgure 95. Conposition of magnetite fromIron bsk batholith In termsof molecular per cent FeO-Fe203-TIOpCr203.

273 Q

4.13

3.0

E P MASSIVE n MAGNETITEHOST 2.0 0) 0 C-.-.-*OSyenite & - Diorite ,

DISSEMINATED 1.0 MAGNETITEHOST \.. Syenite *I.. !I 0...... 0 Picrite ,I.. 1, A------A Diorite 8 0

I I I I I I I I Mg V Ti Mn Cr Ni Co Zn

Figrre 96. Mean minorelermnt content of masslve anddisseminated magnetlte insyenite, dlorlte, and plcrlte,Iron Mask batholith.Error bars shw thestandard error of the man. bta are fromTable 2.

214 Inspectionof figure 95shows that chromium-richmagnetite from picrite has a composition which is distinct from disseminata3 andmassive magnetitein syenite and diorite. me compositionof this; chromium-rich magnetite is similar to compositionsreported formagnetites from basalticrocks (Table Hg-20 in Haggerty,1976).

Lode magnetiteand disseminated magnetite from syeniteand diorite plot in a compactcluster. There is no statistical difference (at 99 per cent confidence limits) betweenthe means andstandard deviation of oxides in disseminatedmagnetite from syenite fromor diorite. Comparison of oxidesindiorite-hosted massive magnetite to those j.n diorite and syenite-hosteddisseminated magnetite shows a significant #difference only in the mean V202 contentand the standarddeviations of Si02, Ti02, and CaO. lhe almostidentical composition oflode and disseminated magnetite fromsyenite and diorite suggests close geneticassociations.

COMPOSITION OF APATITE IN UAGNETITELODES

The apatite analysisin Table 3 is theaverage of six electronmicroprobe analyses of threecrystals of apatitein massive magnetite from the Glen Iron mine (Fig.93). Composition of apatite is uniformbetween crystals. Additionalanalytical traverses from centre to edge of an individual crystal showedno zoning. Glen Iron apatite is fluorinerich, whj~ch is alsotypical of apatite in the magmaticKiruna ironores (Frietsch, 1978).

MINOR ELJSlENTS IN HAGNETITE

Mean minorelement abundances in disseminatedmagnetite from syenite, diorite,syenite plus diorite, and picrite, andminor element abundances in magnetite' fromsyenite and diorite-hosted magnetite-apatite lodes are summarized in Table 4. All variablesreported have lognormal density distributions; consequently, geometric means and CorresFonding standard deviationsare reported. Zero values were assumed to be 0.1 for purposes of log transformations.Copper and leadare not included, due to poor analytical or samplingprecision as revealed by a nestedanalyais of variance(Griffiths, 1967).

Elementabundances in massivemagnetite and in syenitt?,diorite, and picrite-hosteddisseminated magnetite are shown schematically on Figure 96.Several points are well displayed by thediagram, namely:

(1) minorelement abundances are very similar indiorite andsyenite- hosteddisseminated magnetite, (2) minor element abundancesindisseminated magnetite in picrite are markedlydifferent from those in all other magnetite!;, and

275 2 76 (3) minorelements in massive nagnetite show a similar distribution to thosein syenite anddiorite-hosted disseminated maglletite, except forstrong depletion of chromium andtitanium, and weak depletion of vanadium inmassive magnetite.

Statisticalcomparison of means andvariances at 99 per centconfidence limits confirms the previouslydescribed observations and also shows that in sixout of eightelements, abundances massivein magnetite are significantly closer to thosein disseminated magnetite frcmm syenitethan to thosein disseminated magnetite from diorite (Cann,1979).

COIPARISON OF MINOR EL- IN NAGNETITB LODES IN IRON IVSK ~~LI!~ WITe WINOR ELEMENTS Ils UAGNETITE DmOSITS I11 OTHER AREAS

Variances and means ofelements in Iron Mask magnetite-apatitedeposits havebeen statistically compared to thoseof Missouri and Swedish depositsand show that at the 99 per centconfidence level statistical distribution of most minor elements in magnetiteof the 1:ron Uask lodes are similar (Fig.97) to those for magnetitefrom thrt?e deposits in Missouri(Kisvarsanyi and Proctor, 1967) and four deposits in Kiruna, Sweden (Pardk,1975, pp. 199-202). %is statistical simiLarity for most elements is readilyapparent on Figure 97,and reinforcesthe inter- pretationthat Iron Mask magnetite-apatitelodes have an intrusive- magmaticorigin, like the Kiruna and Missouri deposits.

4.0 A.

3.0 E 2.0 m -0

1.0

I Mg V Ti Mn Cr Ni Co Zn

FIgure 97. klthnetlc means of mlna element abrndances In magnetlte from Iron Mssk lodes, and mqmtlc magnetiteapatite deposlts tromMIssouri, U.S.A. and Kiruna, Sweden. See text for reterences to data.

277 SURFACE

b. IMMISCIBLE STAGE 1" vvvvvvvvvvvvvvvvvvv SURFACE

vvvvvv vvvvvv vvvvvv

vvvvvv vvvvvv vvvvvvvv vvvvvvv vvvvvvvvvv vvvvvvvvvv ++++ vvvvvvvvvvv ++++ vvvvvvvvvv ++++ vvvvvvvvvvvv vvvvvvvvvvvvv ++++ vvvvvvvvvvvvvvvv

I SYMBOLS 1 Magnetite-MassiveBrecciaCreek Cherry Apatite (melt, laminated, lode) 1 1ml NicolaAgglomerate r]2-,>;:,,',;' ;I Pothook Diorite ml Iron MaskHybrid

Flyre 98. Dlagrammtlccross-sectlms (lmzklng east) I llustratlnggenesis of magnetite apetltelodes In thenorthwest end of Iron hsk pluton (see Flg. 94). Ibference should be made to the text for descrlptlms of the stages I I lustrateb

278 For statistical comparisonwith Iron Mask magnetitedeposits, minor elementdata for five metasomatic magnetite deposits and one hydrothermal magnetitedeposit in the U.S.S.R. (Borisenko, et dl., 1969) were compiled.'lhese data suggested that metasomatic deposits haveone-hundredth toone-thousandth the nickel and chromium contents of magmaticmagnetite- apatitedeposits and thathydrothermal magnetite deposits have significantly less cobalt and chromium thanmagmatic magnetite deposits.

DISCUSSION

Majorand minor element data on magnetite and petrologicanalysis lead to severalimportant conclusions regarding the genesis ofmagnetite lodes in theIron Mask batholith. A metasomaticorigin can probably be discounted on thebasis of the chromiumand nickel contents,sharp contacts, andthe tabularnature of the lodes. Origin as hydrothermal veins can be discounted on thebasis of higher chromium contentthan other hydroth'ermal veindeposits. Nevertheless, to make theexistence aof 'magnetite- apatite' melt feasibleat geologically acceptable temperatures, a high volatilecontent is probablynecessary. Park (1972) and Geijer(1967) pointedout the apparentlyhigh volatile content ofmagnetite-apatite dykes.Fluorine-rich apatite in Iron Mask dykessuggests that fluorine is a significantvolatile component.

C~LUSIOUS

A model forthe origin of magnetite-apatitelodes is presented on Figure 98. It is based on ourtrace element in magnetitedata and on experi- mental evidencefor magnetite-apatite lodes.

The sequence of events is pictured as follows:

POTHOOK STAGE. Crystalsettling of plagioclase andpyroxene to form Pothookdiorite. With continueddifferentiation the residual magma becomes increasinglyrich in iron as suggested by interst.itia1 magnetite in Pothookdiorite (Table 1).

IMMISCIBLE STAGE. Near the paint where theresidual. magma becomes alkalic in character,the magma enters an immiscibiLityfield that is expanded by highvolatile components (Philpotts, 1967)and the 'oxide-apatite' melt separates from thesilicate magma. The heavy 'oxide-apatite'droplets settle tothe bottom of the magma chamber andcoalesce to form layers and pools in Pothook dioriteat the margins of the magma chamber (see Ramdohr, 1969, p. 8).

MAGNET STGE. Residualalkalic magma,now depleted in iron(Fig. 94;Table l),continues crystallizing as Cherry meek 'syenite.' Extrusion of Nicolaagglomerate containing Cherry ICreek fraqments (Northcote,1977a) occurs and emphasizesthenear surface and

279 cogeneticnature of theintrusion andNicola volcanic rocks. Injection ofmagnetite-apatite melt intofractures formed in the now consolidatedsurrounding intrusion occurs synchronously with eruptions of alkalic magma tothe surface. Such activitymight in part result from increasingvolatile pressures.

(4) AFTON STAGE. Increasingvolatile pressure atthe end of magmatic differentiationexceeds external loadpressure and tensile strength ofthe surrounding rocks (Norton and Cathles,1973) resulting in explosiveemplacement Cherryof Creek breccias. Orthomagmatic hydrothermalfluids follow thebreccia andresult in copper mineralizationatAfton and elsewhere in theCherry Creek unit. Copper mineralization CKOSSCU~S theearlier magnetite lodes.

Comparisonof cross-section D (Aftonstage, Fig. 98) to thesimplified geologicalplan of thenorthwestern end of the batholith(Fig. 94) shows remarkablesimilarities despite the differences perspective.in The deficiency ofmagnetite inCherry Creek syenite compared to Pothook diorite(Fig. 94;'lbble 1) is well explained by fractionation of the immiscibleiron oxides from thealkalic magma that crystallizes to form theCherry Creek unit. The model alsoexplains the close spatial association of thelodes with merry Creek unit as well as their common occurrencewithin or near the iron-rich Pothook diorite.

An importantimplication from the model, regarding the relationship betweenmagnetite-apatite and copper mineralization at Afton, is thatthe same mgma phase was parent to boththe magnetite and copper mineralization.Magnetite lodes were formed before a sulphide-richhydro- thermalsystem became important.Elsewhere in thebatholith magnetite occursfragmentsas in a CherryCreek phase indicating magnetite emplacement was not the last magmatic event to takeplace (Cann, 1979).

Picritesappear tobe more primitive and geneticallydistinct from alkalic and dioriticrocks in the batholith. Thus coppermineralization that is spatially and possiblygenetically related to picrite,such as theIron Mask mine, mightnot be relateddirectly to Afton-type mineralization. This conclusionhasdirect implications to mineral explorationbecause it suggeststhat different geological modelsapply to differenttypes ofcopper occurrences in the Iron Mask batholith.

Our model foriron and coppermineralization suggests that copper mineralization is produced by late-stage magmatic fluidsthat resulted in formation of CherryCreek breccias. A mgmaticorigin for cop er mineralization is supported by Hoiles(1978), who found that the 634 s values of sulphides from theAfton deposit are comparable toother deposits of magmatichydrothermal origin because they are close to 0 per mil with a smallstandard deviation. Alkaline-type porphyry deposits, such as Afton, are known to be significantonly in the NorthAmerican Cordillera in the region from Alaska to Idaho (Hollister,1978). Possibly the unique alteration andmineralogy of alkalicporphyries

280 result from strongdifferentiation, whereas mineralization in .talc- alkalicporphyries is due collapsingto hydrothermal systems that involvedboth meteoric and magmatic waters(Taylor, 1974; Whitney, 1975).

A" A"

The writers thankthe British Columbia Ministry of hergy, Mines and PetroleumResources and NaturalScience and hgineeringResearch Council forsupporting this stody with grants. A. Waskett-Myers assisted in atomicabsorption analyses and J. Knight and L. Pigagehelped with microprobeanalyses. A. J. Sinclairguided the statistical interpretations and critically readthe manuscript.

FsmRmCEs

Badham, J.P.N. andMorton, R. D. (1976):Magnetite-Apatite Intrusions andCalc-Alkaline Magmatism, Camsell River,Northwest Wrritories, Cdn. Jour. Earth Sci., Vol.13, No. 2, pp.348-354. Barr, D. A,, Fox, P. E., Northcote, K. E., andPreto, V. A. (1976): The AlkalineSuite Porphyry Deposits -- A Summary, in PorphyryDeposits ofthe Canadian Cordillera, A. Sutherland Brown, editor, C.I.M., Special Vol. 15, pp.359-367. Borisenko, L. F., Lebedeva, S. I., and Serbodova, L. I. (11369): Titanium Magnetiteand Magnetite of Iron Ore Depositsof Different Genesis, Internat.Geol. Rev., Vol. 11, No. 12, pp.1408-1418. Cann, R. M. (1978): Genesis of MagnetiteDeposits in theIron Mask Batholith, B.C. Ministry of Energy,Mines & Pet. Res., Geological Fieldwork,1977, Paper 1978-1, pp. 86-88...... (1979):Geochemistry Magnetiteof and t'he Genesisof Magnetite-Apatite Lodes in theIron Mask Batholith,British Columbia,unpub. M.Sc. thesis,University of British Columbia, 196 pp. Carmichael, J.S.E. (1967): The Iron-TitaniumOxides ofSalic Volcanic Rocksand theirAssociated Ferromagnesian Silicate:s, Contr. Min. Petrol., Vol. 14, pp. 36-64. Carr, J. M. (1956):Deposits Associated with the Fastern Part of the Iron Mask Batholithnear Kamloops, B.C. Ministry of Energy,Mines & Pet. Res., Ann. Rept.,1956, pp.47-54. Carr, J. M. andReed, A. J. (1976):Afton: A Supergene 'Copper Deposit, in PorphyryCeposits ofthe Canadian Cordillera, A. Sutherland Brown, editor, C.I .M., Special Vol. 15,pp. 376-387. Cockfield, W. E. (1948): Geologyand Mineral mposits ofNicola Map- Area, British Columbia,Geol. Srv., Canada, Mem. 249. Davis, R.E.G. (1962): A MagnetiteBreccia, Galore Creek, Stikine River Area,British Columbia, unpub. B.A.Sc. thesis,University of British Columbia.

281 Ewing, T. (1979): Geology of the Kamloops Group, B.C. Ministly of Energy, Mines S Pet. Res., Geological Fieldwork, 1978, Paper 1979-1,pp. 119-123. Fletcher, K. (1970): Some Applications of Background Correction to Trace Metal Analysisof Geochemical Samples byAtomic AbsorptionSpectro- photometry, Econ. Geol., Vol. 65, pp. 588-591. Frietsch, R. (1978): on the Magmatic Origin of Iron Ores of the Kiruna Type, Sveriqes Geol. Unders., Ser. C, No. 624, 32 pp. Frutos, J. J. andOyarzun, J. M. (1975): Tectonic and Geochemical EvidenceConcerning the Genesis of El LacoMagnetite Lava Flow Deposits, Chile, Econ. Geol., Vol. 70, pp. 988-990. Geijer, P. (1931): The IronOres of the Kiruna Type, Sveriges Geol. Unders., Ser. C, No. 367,39 pp...... (1960) : TheKiruna Iron Ores, in ArcheanGeology of Vastervottenand Norrbotten, Northern Sweden, Geol.Surv., Skreden, Guide to IGC Excursions A32 and C2b. pp. 34-48...... (1967):Internal Features of the Apatite-Bearing Magnetite Ores, Sveriges Geol. Unders., Ser. C, No. 624, 32 pp. Griffiths, J. C. (1967):Scientific Method inthe Analysis of Sediments, McGraw-Hill, 508 pp. Haggerty, S. E. (1970): The mco Magnetite Lava Flow, Chile, Geoph. Lab., Ann Rept., 1968-1969, pp. 329, 330...... (1976) : Opaque Mineral Oxides in Terrestrial IgneousRocks, in Oxide Minerals, D. Rumble 111, editor, Min. Soc. dm., Short Course Notes, Vol. 3, pp. 101-300. Hoiles, H. K. (1978):Nature and Genesis of the Afton Copper Deposit, Kamloops, British Columbia, unpub. M.Sc. thesis, University of Alberta. Hollister, V. F. (1978):Geology of the PorphyryCopper Deposits of the Western Hemisphere, A.I.M.M.E., 219 pp. Kisvarsanyi, G. andProctor, P. D. (1967):Trace Element Content of Magnetitesand Hematites, SoutheastMissouri Iron Metallogenic Province, U.S.A., Econ. Geol., Vol. 62, pp. 449-471. Kolker, A. (1982):Mineralogy and Geochemistry ofIron-Titanium Oxide and Apatite (Nelsonite) Deposits andEvaluation of theLiquid ImmiscibilityHypothesis, Econ. Geol., Vol. 77, pp. 1146-1158. Llaumett, C. (1967): Los Dep6sitosde Fierro de El Laco, Provinciade Antofagasta, Chile,Cia. Minera, unpub. rept. Mathews, W. H. (1941):Geology of the Iron Mask Batholith, unpub. M.A.Sc. thesis, University of British Columbia, 42 pp. McMillan, W. J. (1978): Nicola Project, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1977, Paper 1978-1, pp. 26-30. Montgomery, J. H. (1967):Petrology, Structure, and Origin of the Copper MountainIntrusions near Princeton, Eritish Columbia, unpub. Ph.D. thesis, University of British Columbia, 172 pp.

282 Nakagawa, H. M. (1975): Atomic AbsorptionDetermination of Silver, Bismuth, Cadmium, Cobalt,Copper, Nickel, Lead,and 'Zinc in Calcium andIron-Rich Geological Materials, in New and Fafined Methods ofTrace Analysis Useful in GeochemicalMploration, F. N. Hall, editor, U.S.G.S., Bull. 1408,pp. 85-96. Northcote, K. E. (1975):Geology Of NorthwestHalf of Iron Mask Ehtho- lith, B.C. Ministry of Energy, Mines S Pet. RE~S., Geological Fieldwork,1974, Paper 1975-1, pp.22-26...... (1977a):Iron Mask Batholith, B.C. Ministry cd Energy,Mines & Pet.Res., Prelim. Map 26...... (1977b):Geology of Southeast Half ofIron Mask Batholith, B.C. Ministry of Energy,Mines & Pet.Res., Geo1og:icalFieldwork, 1976, Paper 1977-1, pp.41-46. Norton, D. L. and Cathles, L. M. (1973):Breccia Pipes-Products of Exsolved Vapor from Magmas, Econ. Geol., Vol.68, pp. 540-546. Pardk, T. (1975) : The Origin of theKiruna Iron Ores, Sveriges Geol. Unders., Ser. C, No. 709,209 pp. Park, C. F. (1972) : The Iron Ore Depositsof the Pacif:tc Basin, Econ. Geol., Vol.67, pp. 339-349. Philpotts, A. R. (1967):Origin Certainof Iron-Titallium Oxideand Apatite Rocks, Econ. Geol., Vol.62, pp. 303-315. Preto, V. A. (1968) : Geologyofthe Eastern Part of theIron Mask Batholith, B.C. Ministry of Energy,Mines & Pet.Res., Ann. Flept., 1967, pp. 137-147...... (1972a):Report on Afton,Pothook, B.C. Ministry of Energy, Mines S Pet. Res., GEM, pp.209-220...... (1972b) : Geology of Copper Mountain, B.C. Ministry of Energy, Mines S Pet.Res., Bull. 59, 87 pp...... (1977): The Nicola Group: MesozoicVolcanism Related to Rifting in SouthernBritish Columbia, in VolcanicRegimw in Canada, W. R. Baragar, L. C. Coleman,and J. M. Hall, edi.tors, Geol. Assoc. Can., SpecialPaper 16, pp. 39-57. Ramdohr, P. (1969) : TheOre Minerals and theirIntergrowths, Pergamon Press, 1174 pp. Ringwood, A. E. (1955) : Ihe PrinciplesGoverning Trace Element Beha,viour During Magmatic Crystallization,Part 11: The Role Complexof Formation, Geochim. et Cosmochim. Acta, Vol. 7, pp.242-254. Rucklidge, J. C. andGasparrini, C. (1969): EWAADR VII: Specifica.tions of a ComputerProgram forProcessing Electron Microprobe Data, University of Toronto. Ruiz, C. (1965):Geologia yYacimientos Metaliferos de C'lile, Sant.iago, Inst.Inv. Geologicas, 305 pp. Schau, M. (1970):Statigraphy and Structure of the Type Area ofthe Upper TriassicNicola GroupSouth-Centralof British Columbia, in Structure of theSouthern Canadian Cordillera,. J. 0. Wheeler, editor, Geol. Assoc. Can., SpecialPaper 6, pp.123-135.

283 TaylorJr., H. P. (1974) : IheApplication of Oxygenand Hydrogen Isotope Studiesto Problems of Hydrothermal Alteration and Ore Deposition, Econ. Geol., Vo1. 69,pp. 843-883. Whitney, J. A. (1975): Vapor Generationin a Quartz Monzonite Magma: A Synthetic Model withApplication to Porphyry Copper Deposits, Econ. Geol., Vol. 70,pp. 346-359. Young, G. A. and Uglow, W. L. (1926): The Iron Gres of Canada, Geol. Surv., Canada, Econ. -01. Ser., No. 3, pp.109-128.

284 A coIpU'J!ER-BASED PROCEDURE POR QUANTIFYIYG GEOLOGICXL DATA FOR RESOURCE ASSBSSUENT

BY A. J. Sinclair and A. Bentzen Department ofGeological Sciences, The Universityof Br.itish Columbia

IUTRODUCTIOII

A computer-basedprocedure is describedfor quantifying geological data as a preludeto resource assessment. The method involves: (1) digitizing geologicaldata, and (2) a series programsof to make quantitative estimates of areas and distanceswith geological signific,snce. Procedures describedare general in naturebut in ourimmediate case are being appliedto the GuichonCreek batholith(including the Highland Valley porphyrycopper area) as a basisfor resource assessment.

A common methodof coding geological information for inclusion in quantitativeresource assessment andexploration modelling is tosuperimpose a squaregrid on a geological map and recordcharacteristics pertaining to each cell of thegrid (see Agterberg,1981). Such a procedure ha.s been used by Kellyand Sheriff (1969) in theirefforts to outline 20 mile by 20 mile cells in British Columbia,having a highmineral potential. At a differentscale Sinclair andWoodsworth (1970) coded geologicalinforma- tion from theTerrace area relative to a gridwith a cell size of i! miles by 2 miles. In a directapplication to porphyrycopper evaluation, Godwin and Sinclair(1979) developed a file ofgeological, geochemical, andgeophysical data for the Casino porphyry copper-mol'fbdenum deposit, Yukon Wrritory, relative to 400 foot by 400 foot cells of an explclration grid on the property. All the foregoingstudies and mnyother c:ompar- ableinvestigations havebeen directed toward a quantitativeapproach to resourceevaluation in which some measure of value ofa cell is related to geologicalto and othervariables coded forthat cell. Types of geologicalvariables recorded are generallyfound irk thefollowing categories:

(1 percentage of a cell underlain by a particular rocktype, (2) distance from cell centre to a specificgeological feature, (3) spatialdensity values, for example, fracture density, (4) lengths of contacts,fractures, etc., in a cell, and (5) (projected)absolute areas of nearestspecific rock units, etc!.

Two problems in a manualapproach to codingof geological informati.on for cells of a gridare: (1) it is tedious andtime-consuming, and (2) manual methodsare prone to mechanical errors, many ofwhich arenot readily identifiable in normalediting procedures. To overcome these probl.ems we havedeveloped a computer-basedapproach for the estimation of geol.ogica1 andother variables for Cells ofa grid. This work is, a preludeto a quantitativeresource assessment of the GuichonCreek batholith and early results of thisstudy will provideexamples of our procedure.

285 DIGITIZING and EDITING GEOLOGY

MEASURE GEOLOGICAL VARIABLES

~i~re99. FI~ chart I I lustrating the general conputer-based system for generating a file of quantitative geological masurenents as a prelude to resource assesYnent.

PROCEDURE

Our generalsystem, as outlined in theflow chart on Figure 99, includes tw main elements:

(1) digitizing and editing of map information,and (2) developnentof a series ofsubroutines to make measurements relative to an arbitrarygrid and digitizeddata.

The principaladvantages of themethodology are its consistencyand the easewith which a variety of editingprocedures can beemployed. An importantfeature is that new combinations,of variables can be obtained rapidlyif information is digitized,whereas normal methods would require anadditional tedious effort ofmeasurement. Perhaps most important is thefact that sensitivity of cell size on resourceassessment is more feasiblewith a computer-basedas opposed to a manualapproach.

DIGITIZING GEOLOGICAL- INFORMATION

The digitizingprocedure is illustratedwith reference to the Guichon Creekbatholith resource assessment study. All phasesand varieties of batholithicrocks were digitizedusing Preliminary Map 30 (B.C. Ministry

286 ofEnergy, Mines and Petroleum Resources, McMillan, 1978) whichcontains the most detailed andup-to-date geological information available on the scale of the entire batholith. The digitizingprocedure was tooutline each separate area ofa givenphase by a closedpolygonal outline with as many pointsas necessary to honour the level of detail of thebase map. Verysmall areas of younger or older rock were ignored.

Editing of digitizeddata involves a variety of proceduresincluding: (1) separatingdigitized polygons with end-of-polygon flags, (2) collec- tingpolygons representing the same geologicalunit into a single file, (3) closingthe polygons, (4) reversingpolygons if necessary so that all aredigitized in consistentfashion (for example, counterclockwise), and (5) deletion of incorrectpoints in a polygon. The digitized po:tygons were thenplaced in numbera of separatefiles, one foreach geological unit andmachine-drawn maps were preparedfor each unit. as a final editingstep (Fig. 100). These maps were produced tothe same scaleas thebase map and were compared visually(using a lighttable) wit-h the base map.

Flyre 100. Conputercontrolledplot of dlgltlzedareas underlain by the Borderphase of the @ichm Creek batholith, central Brltlsh Calmbla. An 'A' nearthe northwestern corner of the map Is centred on Ashcrof t and a 'C,'Just below theswthernnust ewosure, Is centred on Cralgnunt pit. bta dlgltlzed from McMIIlan (1978).

287 MEFSUNBlENT OF GEOLOGICAL VARIABLES

Cur conputerizedapproach to resourceassessment inwhich geological variablesare referenced to systematic grid cells, depends on a series of computerprograms designed tomeasure geological variables (Fig. 99). Some of the procedures aredescribed briefly to illustrate the nature of variablesthat can be measuredand togive some indicationofthe potential wide range of applications of our conputerizedapproach.

Withincell area measurements. A grid of stipulatedcell size is superimposed on a 'map'of single rock categoryand the proportion ofeach cell underlain by the rocktype is calculated. The pro- cedureused for one geological unit is to move systematicallyalong eachpolygon recognizing the intersectionswith grid cell boundaries. Ihe part of a cell area within a polygon is then determined. After all polygons havebeen treated in this manner, a set of cells remains for which no area estimates havebeen made. They are checkedsystematically and ifthe cell centre is within a polygon, anarea of 100 percent is assigned;otherwise an area of zero is assigned. If thereare islands of otherrock types within a polygon, the areaoccupied by these is subtractedautomatically. The result is a file of the per cent of area ofeach cell underlain by a specific rocktype. Repetition of theprocess for other rock units results in a quantitative file of geological'areas' per cell.

Lengthof contacts (dyke, fracture, etc.) in a cell.Variables of this typeare very straightforward tocalculate from digitized contacts. Ehch polygon is examinedand its intersectionwith grid cellboundaries used to define a segmentof a polygon in which point-to-point distances will be summed to provide a length.

Distance from cell centre to a specific geologicalfeature. This process involveschecking whether a cell centre is within or outside the limits of a particulargeological feature. If the centre is not enclosed in polygonsof a particulargeological feature, then the shortestdistance from the cell centre to the nearest partof the nearestpolygon is determined.

Programs toacconplish the foregoing types of measurementinclude the majority of variabletypes outlined in theintroduction. Other useful types of quantitative measurementscan beadded asdesired. We are presentlygenerating a quantitativedata base for the michon Creek batholithusing a cell size of 2.59 squarekilometres (1 square mile). Thisup-to-date geological data base will bemerged with our existing filefor geophysical andgeochemical data based on the same gridsize, and will providethe fundamental information for a resourceassessment in the GuichonCreek batholith.

288 mucLusIous

A computer-basedapproach to the quantitativemasure of geological variablesas a basefor resource assessment has been established., The procedureinvolves two majorcomponents: (1) digitizingof geological features, and (2) a variety ofprograms designed to extract quantitative measurements of geologicalvariables relative to cells of a reference grid. A variety of editingprocedures are built into the system.

We are presentlyapplying the procedures to anassessment of resources in the GuichonCreek batholith(including the long established porphyry copper area of theHighland Valley). Of course, the proceduresand soft- ware are general in nature and potentially have much widerapplication notrestricted to geologicalvariables.

AcKMwLEDGIIERTs

Thisstudy is funded by the ScienceCouncil of British Columbiaand is part of the MINDEP project ofcomputer-oriented, mineral deposit studies done in cooperationwith the MineralResources Division of the Eritish ColumbiaMinistry of Ehergy,Mines and Petroleum Resources. Some assistance in computerprogramming was obtained from KT. mi Ulenof International GeosystemsCorporation, Vancouver, whichfor we are grateful.

REPKREIYI'ES

Agterberg, F. P. (1981): Cell Value Distributionbdels in Spatial PatternsAnalysis, in Future Trends in Geomathematics, R. G. Craig and M. L. labovitz,editors, Pion Ltd., London, Ehghnd, pp. 5-28. Godwin. C. I. and Sinclair, A. J. (1979): ApplicatkonMultipleof RegressionAnalysis Drill-Targetto Selection, 'casino Porphyry Copper-Molybdenum Deposit, Yukon Territory, Canada,Trans. Inst. Min. Met., Sec. B, pp. B93-B106. Kelly, A. M. and Sheriff, W. J. (1969): A StatisticalEmmination of the MetallicResources of British Columbia, Proceedingsin of a Symposium on Decision-Making in MineralizationExploration 11, A. M. Kelly and A. J. Sinclair, editors,Mtension Dept., University af British Columbia, February 6, 7, 1969, pp. 221-243. McMillan, W. J. (i978): Geologyof the GuichonCreek BathoWth and HighlandValley Porphyry Copper District, British Columbia, B.C. Ministry of Energy,Mines & Pet. Res., Prelim. Map 30. Sinclair, A. J. andWoodsworth, G. J. (1970): MultipleRegression as a Method ofEstimating Exploration Potential in an Area nearTerrace, British Columbia, Econ. Geol., Vol. 65, pp. 998-1003.

10 289 290 RESOURCE ASSEsSUBNl' OF GOLL+QUART!4 VEINS, ZEBALLOS HINING CAW VAW2OWER ISLAND - A PRELIMINARY ILPPORT ( 921)

By A. J. Sinclair and M. c. HMsen Department of GeologicalSciences, The Universityof British Columbia

1N"RODWCTION

Productiondata and variousgeological measurements have been compiled andtabulated for gold-quartz veins of theZeballos mining camp, Van- couverIsland, British Columbia. A preliminaryqualitative evaluation of some of thesedata indicate that: (1) mined tonnage i!; an acceptable relativevalue estimator, (2) on average,large deposits are lowergrade thansmall deposits, (3) goldand silver are highlycorrelated, (4:l gold grade is relatedsystematically to bulk sulphide content as indicated by average combined leadplus copper, and (5) animportant systematic relation exists betweengold content of a deposit and distance from the contact ofthe Zeballos stock. A quantitativeevaluation ofthese data is in progress.

Zeballosmining camp is on the west coast ofVancouver Islandabout 320 kilometresnorthwest of Victoria,British Columbia.Access is via an all-weatherroad between the settlements of Zeballos (5 kilometressouth ofthe mining camp)and Nimpkish. The surroundingcount.ryside is mountainous and ruggedwith elevations from nearsea level to about 1 30L metres; it experiencesmild winters and highrainfall.

The first gold-quartzvein staked in the area was theTagore in 1924 althoughlimited quantities of placergold hadbeen mined previously. Lode productionbegan in 1934 and reached a peak in 1937 to 1943. By 1948 most production had ceased. Two deposits,Privateer and Spud valley,have produced 473082 of the 651797 tonnesof ore mined in the camp.

Recordedmetal production to datetotals 9 465244 gramsof go1.d and 4 119 118 gramsof silver,as well as minoramounts of copperand lead from a total of 651797 metric tonnes of ore mined. Thistonnage includesthe substantial dilutionresulting frommining veins commonly about 10 to 30 centimetres wide.Average mined gradesfor the cam,ps are 15 grams goldper tonne and 6.5 grams silver per tonng? althoughvein materialcontained as much as 30 to 150 gramsgold per tonne.

Our evaluation Zeballosof camp is oriented toward a quantitative resource assessment followingthe approach of Sinclair (1979), Goldsmith, et dl. (in preparation), and Orr and Sinclair (1971) . The study is dividedinto two parts: (1) developmentof a quantitativedata file, and

291 0 0

MINED TONNAGE (tonne)

Flyre 102 Average goldgrade per tonne mlned (graffi per tonne) versusmlned tonnes, &baIlosrnlnlng cam. lhree deposlts wlth tonnages of 2, 1, and I and correspondinggold grades of 70, 156, and 156 grans per tonne are not Included In the plot.

~ig~re103. Plot of preciousmetal contents versus mined tonnes, hballosmlnlng cam.Gold contents are shown wlth clrcles and slivercontents by triangles.

292 (2) evaluationof quantitative data. ?his report describes the det.ailed datafile and presents some ofour initialresults stemming f:rom a preliminaryevaluation of the file.

GEOLOGY OY ZEaAuos CAW

Generalgeology of the area in andaround Zeballos camp is shown on Figure 101. The area is underlain by anessentially monoclinal sequence ofKesozoic volcanic and sedimentary rocks cut by Jurassic and Wrtiary intrusions. The Iawer Jurassic Bonanza soup is a typ:icalisland arc sequenceof largely basaltic to rhyolitic volcanic rocks. This unit is underlainconformably by limestonestheofplatsino Formation and tholeiiticbasalts of the Upper Triassic Karmutsen Group. All these rocksare cut by Jurassicplutons ofthe Island intrusions, l~inly dioritic andgranodioritic in composition. The Zeballosstock, with its spatiallyrelated gold-quartz veins, is a quartzdioritx phase of the Catfaceintrusions of Eocene age.

A QUANTITATIVE DATA BASE

We haveestablished a quantitative data base relating to mineral deposits andoccurrences in Zeballos campby referenceto 'two sourcesof information: a report and map by Stevenson (1950), ,and the MINFILE computer file of mineraldeposits in British Columbia.In additionto numericaldata relating to grades andtonnage mined and/ormilled, we have made numbera of othermeasurements ofa geologicalnature from Stevenson's (1950) map, aswell ascoding mineralogical information. Thesedata are summarized in Tables 1 to 5, where depositsare listed in order ofdecreasing tonnage mined. The tablesare self-explanatory but some comments on the nature and quality of dataare warranted.

Mined tonnage refers to ore brought to surface and :subject tc hand sortingprior to milling. Quoted gradevalues refer to minedtonna.ge.

The two most productivevein orientations are shown foreach deposit; eachorientation may representseveral veins. In general, an effort was made to record mean directions of undulatorysurfaces.

Vein widthrecorded in Table 3 appliesto the mostproductive segment of a vein;thus, is a subjectivevariable ofuncertain value. The term

'sheetedzone' refers to I... jointsspaced 2 to 8 inchesapart and (which)contain either gouge orquartz-sulphide stringers an eighth ofan inchto an inch wide' (Stevenson, 1950). %nsionalfeatures include gash veins and comb quartz.Associated replacement/alteration category refers tofeatures observed in a veinor adjacent wallrock such as silicifi- cationoroxidation. Ingeneral, such data are sparse in available literature.

293 0 $W ? C 0 4- .(51 Y W 0 4 a (3 aT1 W a0 a >W t 111111 I I ,,,I I a 1 5 10 50 100 500

AVERAGE Ag GRADE(g/tonne)-MINED

Flplre 104. Average goldgrade (gram per tonne) versus average sllver grade (grams per tonne) for gol&quartr velns, Zeballos rnlnlng cam.

E $ t 0 .. 100 a, 100 r E 0 C 0 50 ' !!I 50 .(51 Y W 0 0 a 0 0 a a, 0. (3 10 : e 3 a 5- W MAJOR PRODUCER a(3 0 OTHER a W a 1 I ,,,,I I ,,,,I I ,,,,I 0.001% 0.01% 0.1% 1.0%

AVERAGE COMBINED Cu+Pb GRADE(%)-MINED

Figre 105. Average goldgrade (gram per tonne) versus cmblned lead plus copper(per cent) for gole-quartz velns. Zeballos mlnlngcaw. Ceposlt 17 (Cordova) Is Included In thls plot.

294 Distances of variousdeposits from thecontact of theZeballos stock were measuredfrom Stevenson's (1950) geologiCa1 map of the camp (st2e Fig. 101). In a few casesthe contact had tohe extended across drift-[!overed areas in order to obtain distance measurements.

PRELIMINARY EVALUATIONOF 2EBALU)s DATA BASE

Thereare many blanks in Tables 1 to 5, particularlyas regards tograde andtonnage information. Completeproduction statistics exist foronly nine of 18 depositswith recorded production. Consequently, it will be difficult,if not impossible, to apply some of thetechniques of evaluation recommended by Sinclair ( 1979) forvein camps.

Instead, we havechosen to examinevarious plots as a '5asisfor a sub- jectivepreliminary evaluation ofthe data. Some of thesegraphs appear to establishto important relations concerning deposit 1ocatj.on or attributes.Figure 102 is a graph of averagegold grades versus mined tonnages. A size ofabout 2 000 tonnesclearly divides the deposits into tw sizecategories with different mean gradecharacteristics. The high tonnagecategory has a lowergrand average grade and less dispersion of averagegrades than the low tonnagecategory. Some of thisdifference may be the result of selective miningand/or hand sorting.

Preciousmetal contents (gold and silver) are plottedversus production (minedtonnage) on Figure 103. This graphdemonstrates that wherepro- ductionhas been reported, both gold and silver metal contents increase systematicallywith an increase in size;consequently, production tonnage is anacceptable single measure of relative value of vein deposits in the Zeballos camp (see Sinclair, 1979).

Figure104 is a plotof average gold grade versus average silver grade anddemonstrates: (1) theconsistently lowergrade in silver compared with gold,and (2) thepositive correlation between :tog gold .and log silver.This correlation may be partlyartificial; as indicated earlier, some of the highgrades for small deposits may bethe re:gult of selective upgradingof ore. This possibility is suggested by the two clusters of points on Figure104; such patterns represent dubious correlations. Even ifthis explanation is correct, it appearsthat a reasonablecorrelation exists betweengold and silver demonstratedas by thefive major producers in the camp.

Averagegold grade of tonnes mined is plotted against co.pper pluslead on Figure105 where there is a suggestion ofa regularrehtion betweenthe two. In general,precious metal grade is higher if copperplus lead is alsohigh. lhe relation does not appear to be linear on thelog-log plot suggestingthat the effect is not due solely to hand sorting of ore.

Figure 106 is a plot of depositrelative value (total gramsof gold per deposit)versus distance from the contact of theZeballos stock. The graph showsa remarkably consistentpattern both in theZeballos stock and inthe country rock. The fiveprincipal producers are localized within 500 metres of the contact and smallerproducers are moreremoved fromthe contact in a surprisinglyregular pattern. lbese trends can be approximated by thefollowing linear equation:

Within Stock: log(Tota1 gold) = -0.0029D + 6.778 Within Wallrock: log(Tota1 gold) = 0.0025D + 6.778

wheregold is in grams, D is a positivedistance into the stock or a negativedistance into thewallrock measured in metres. lhese equations provide a meansof contouringexpected gold content of deposits remaining to be discovered. As suchthey outline a zoneabout the contact of the Zeballosstock that has high potential for relatively large new gold- quartz veins. The expectedtarget in this zonecan be estimated from Figure102 to have a potential of 25 000 to 250 000 tonnesof ore grading about10 to 20 gramsgold per tonne. A median depositwuld contain about 75 000' tonnesgrading 12 grams gold per tonne. lhe grossvalue of gold in this median deposit,assuming a price ofCanadian dollars 450 per ounce, is about$12 000 000.

DISTANCE FROM CONTACT(m.1

Figure 106. Total goldcontent (grams) versus distance of goldquartz veins from contact ofZeballos sto& (2.S.) withpreTertlary rocks (P.T.R.). Posltlve dlstances are wlthln the stock; negatlve dlstances are wlthln country rock. bposlts greater than 2000 mined tonnes are closed clrcles, smaller deposlts are are open circles.

296 TABLE 1 LISTING OF XINEIU',DEPOSIT DATA FILE FOR ZEBALLOS XINING CW? - GENERAL INFORWTION

YEARS OF DEPOSIT DEPOSITLOCATION MINFILE REF.PRODUCTIOE; ELEVATION NAME UTMN UTMENUMBER UTMN NAME ( 19-) (FEET)(METRES) 1 PRIVATEER4340056600092L/008 34-53.75 750 229 2 SPUD VALLEY 4240058000 092L/012 36.39-42.512000 610 3 MOUNT ZEBALLOS42000 57000 092Lj012 39:42,44' 2000 610 4 CENTRALZEBALLOS 44800 58700 092L/018 38-42.46.C?..1500 457 5 PRIDENT 4350056900092Lj009 41-43,47,48 4571500 6 C.D. 092L/0155810038-4143300 1400427 7 HOMEWARD 42700 60400 092t/019 41,42 2000610 8 VANISLE 43100 55400 092L/038 40 600 183 9 WHITE STAR 43200 57100 092L/010 35-42.52.57.. 1500457 10 ZEBALLOS PACIFIC 42900 57500 092Lj01 1 34 1500 457 11 GOLDENPORTAL 4090055200 092L/005 40 750 229 12 092E/0025630040600BEANO 48,49 2500 762 13 I.X.L.13 43400 57300 2000610 14 RIMY 43300 58700 092L/016 38 762 2500 15 TAGORE 41100 54300 092L/006 30,32,39 400 122 16 BARNACLE 46700 55300 092L/029 2400732 CORDOVA 45800 55500 092L/027 39 2000 6102000 17 092L/027 3955500CORDOVA45800 18 KINGMIDAS 47700 58000 092Lj020 40 500 152 19 ANSWER 4040054600 092E/023 350 107 20 BRITANNIA4190058300092L/013 1900 579 21BIG STAR 4230059300 092Lj017 2500 762 22 MONITOR 42600 57300 1500 457 23 NORTH FORK EXPL. 48800 57800 092L/021 750 229 24GOLD SPRING 47600 57300 1750 533 25 BODEN 44300 54400092L/022 1200 366 26 MAQUINNA26 44800 55300 092Lj023 600 183 27 OMEGA27 45500 54600 092L/024 1400 427 28 PANDORA28 45300 55700 092L/026 a50 259 29LUCKY STRIKE 47300 54500 092Lj030 3750 1143 30 FRIEND30 39200 57800 092E/003 2500 762 31 P.ROSPERITY 41 400 55500092Lj007 1000 305 32 PEERLESS 45300 54200 092L/025 1900 579 33 F.L./RIDGE 46200 55000092L/028 2600 793 34 CHURCH1 LL 47400 55800092L/031 2250 686 35 47100CAVALIER 55800 092LjO32 2500 762

NOTE: 1. DEPOSITS 1 TO 5 REFERRED TO AS MAJOR PRODUCERS. DEPOSITS 6 TO 18 REFERRED TO AS MINOR PRODUCERS. DEPOSITS 19 TO. 35 REFERRED TO AS PROSPECTS. 2. BLANKS INDICATE NO AVAILABLEDATA, ORNON-APPLICABLE VARIABLE/ATTRIBUTE. 3. DEPOSITS 1 TO 30 & 34 ARE GOLD-QUARTZ VEIN PASTE'RODUCERS OR PROSPECTS. THE CHURCHILL PROPERTY ALSO COVERS MAGNETITE REPLACEMENT MINERALIZATION. THE BEANO PROPERTY AIS0 COVERS SKARN-TYPE MINERALIZATION. THE PROSPERITY PR0PER:IY SHOWS NO SIGN OF MINERALIZATIONAT ALL, BUT IS INCLUDE11 FOR THE SAKE OF COMPLETENESS. DEPOSITS 33 & 34 ARE MAGNE?ITE REPLACE- MENT DEPOSITS, AGAIN INCLUDED FORSAKE OF COMPLE?ENESS.

297 T.4BLE 2 LISTING OF MINERALDEPOSIT DATA FILE FOR ZEBALLOS MINING C&V - PRODUCTION DATA

PRODUCTION TOTAL METAL CONTENT GRADE DEP(TONNES ) (GRAMS) (KILOGRAMS) (Gr,Kg/TONNE MINED) NO MINED MILLED Au Ag Cu Pb Au Ag Cu Pb 1 282328146798 5301289 2160196 4063 10093 18.7 7.7 .01 .04

2 19075495876 1682859~~~ 575219 ~ ~~. 9195 8093.05 3.0 8.8 .04 3 7426851540 946589 444399 2408 12726 12.7 6.0 .03 .17 4 5259637789 636773 432238 7370 711401.35 .I4 8.212.1

5 21 ~~~ 585 433440 239812 20.1 11.1 6 4055645 143074 44322 470 2982 7.925.3 .53 .08 7 13753586 46374 108705 318 347 12.930.3 .09 .IO 8 3044 35929 16470 11.8 5.4 9 1293 220987 92531 1563 17144 171.071.6 1.21 13.25 10 28.0393 I1 174 11 22 373 1561.77 2.00 7.141 17.0 39 21 3297 12 21 1400157.0 33 66.7 1.57 13 20 14 93.317 80.5 1369 1586 15 14 20221245 23 20 89.0 144.4 1.64 1.43 16 2 140 70.0 17 1 31 156 0 4 31.0156.0 4.00 18 1 156 31 IO 156.0 31.0 10.00 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

298 TABLE 3 LISTING OF XINEIWLDEPOSITS DATA FILE FOR ZEBALLOS MINING CAW - GEOLOGICAL FEATURES OF HOST RO(:K

DIST(M)/BRG HOSTROCK TYPE FROM NOSE DEP (I) (C) HOST ROCK OF Z.STOCK NO Tg Jg 1JB 1JB uTrQ muTrK STRIKE DIP D/DRN DYKES DIST BRG .1 1 2 0 3 2 0 0 010 60 270 5 1700 185 2 3 0 1 0 0 0 1 3400160 3 0 0 3 2 0 0 160 90 2 3400 175 4 3 0 0 0 3 3 3 2270 110 5 3 0 2 0 0 0 2 1890 170 6 3 0 0 0 0 0 2 2650 150 7 3 0 0 0 0 0 2 4730 125 8 0 0 3 0 0 0 135 80 045 2 2650 210 9 3 0 0 0 0 0 2 2270 170 10 3 0 0 0 0 0 5 2650 165 11 0 0 3 0 0 0 3 4910 200 12 0 0 3 3 0 0 360 80 090 2 El00 185 13 3 0 0 0 0 0 5 2270 165 14 3 0 0 0 0 0 2 2840 135 15 0 0 3 2 0 0 080 80 000 3 4910 212 16 0 2 3 0 0 0 5 1890 315 17 0 3 0 0 0 0 2 1130 295 I8 0 0 0 0 3 5 2 i:650 035 19 0 0 3 0 0 0 2 E1480 205 20 3 0 1 0 0 0 5 1130 160 21 3 0 0 0 0 0 1 4160 140 22 3 0 0 0 0 0 5 5670 120 23 0 0 0 0 0 3 5 24 0 0 0 0 0 3 145 60 2 2'5 3 ;!270 020 25 0 0 3 0 0 0 5 ;!460 245 26 0 3 3 0 0 0 060 75 360 5 1520 250 27 0 2 3 0 0 0 050 80 135 :510 275 28 0 3 0 0 0 0 950 270 29 0 0 0 0 0 0 3 3030 310 30 0 0 3 3 0 0 135 50 225 2 31 0 0 3 2 0 0 135 90 0 4350 196 32 0 0 3 0 0 0 2 2650 270 33 0 0 3 0 3 0 3 34 0 3 0 0 3 0 150 45 045 3 2080 340 35 0 3 0 0 3 0 5 HOST ROCK TYPE;Tg - TERTIARY CATFACE INTRUSIONS (ZEBALLOS STOCK); Jg - ISLAND INTRUSIONS; 1JB - BONANZA GROUP(I-::GNEOUS, C-CALC-SILICATE OR CARBONATE); uTrQ & muTrK - QUATSINO FORMATION L KARMUTSEN FORMATION OF THE VANCOUVER GROUP. 0 - ABSENT: 1 - PRESENT: 2 - MINOR: 3 - MAJOR: 5 - PRESENT TO AN UNKNOWN'EXTENT DYKES,PRESENCE OF DYKES OF VARYING COMPOSITION; 0 - ABSENT; 1 - PRESENT 2 - MINOR: 3 - MAJOR; 5 - PRESENT TO AN UNKNOWN EXTENT DIST FROMN0SE:BEARING L DISTANCE FROM NOSE OF INTRUSION TO DEPOSIT

299 TABLE 4 LISTING OF MINEPAL DEPOSITS DATA FILE FOR ZEBALLOS MIXING CAik - GEOLOGICAL FEATURES OF VEINS

NO AVVEIN AV SHEAR DEP MAJORVEIN/S 2NDARY VEIN/S MINZ WIDTH(CM) ASSOC WIDTH(CM)

NO STRIKE DIP DAJRN STRIKE DIP~~ D/DRN VEINS MIN MAX ZONES MIN MAX 1 65 065 80 180 5 15 30 1 30 90 2 80 070 85 315 3 15 20 1 10 60 3 045 70 135 045 90 2 5 8 1 5 60 4 090 75 180 1 20 25 1 8 45 5 040 80 135 180 80 225 3 2 12 1 30 90 6 045 80 135 0 60 60 315 7 8 12 1 10 45 7 090 85 360 090 90 5 0 30 1 25 75 8 045 75 315 032 80 315 2 3 30 1 3 30 9 040 75 135 040 80 135 2 1 15 1 3 90 10 035 90 057 80 315 7 1 20 1 5 75 11 160 70 045 1 0 15 1 4 20 12 000 90 4 13 040 75 I35 1 1 10 1 3 90 14 095 80 180 080 90 2 3 8 1 3 25 15 045 90 1 0 35 2 16 000 90 000 65 135 4 5 10 1 5 60 17 063 80 135 1 0 25 I 5 45 18 176 90 000 90 5 0 8 I 10 20 19 057 75 315 090 90 3 2 5 I 3 5 20 050 90 060 80 315 4 1 3 1 10 60 21 090 90 090 90 10 0 5 I 156 1500 22 23 010 75 045 1 3 12 1 15 25 24 175 60 135 030 70 135 2 3 20 1 15 20 25 090 72 360 1 5 15 1 15 60 26 090 80 360 1 5 15 1 45 75 27 052 80 135 1 5 10 1 IO 30 28 058 90 1 0 10 1 15 la0 29 047 90 050 90 2 4 8 1 5 15 30 160 70 I35 050 90 3 5 10 1 15 60 31 32 065 90 1 5 5 3 33 4 34 155 60 225 I 0 30 1 50 75 35 4

ASSOCIATED ZONES; 1 - VEINS INTIMATELY ASSOCIATED WITH SHEAR ZONES; 2 - VEINS ASSOCIATED WITH DILATANT ZONES;3 - MINERALIZATION ASSOC- IATED WITH CONTACTZONE: 4 - ASSOCIATED REPLACEMENT (SKARN) ZONE

300 TABLE 5 LISTING OF 14INERrV. DEPOSITS DATA FILE FOR ZEBALLOS MINING CX- - VEIN:4INERALOGY AND CHARACTER

DIST(M) DEP ASSOCIATED VEIN MINERALS SH'TD VEIN TENL TO NO Pyr Sp Aspy Py Cpy Gn Qtz Cc Ank ZONES FORM FEAT REPL CONTACT 1 121312323 3 2 32+ 57 2 020202300 2 2 3 0 + 473 3 003300322 0 2 3 3 - 473 4 5005333002.2 23- l!jl 5 030302300 0 1 3 0 + 4'73 6 022322300 0 2 2 0 +I 2:29 7 023302300 0 I 2 0 + 964 8 232303320 2 4 5 0 -1229 9 022223300 0 1 3 0 + 529 10 022202300 2 2 2 0 + 431 11 330212320 0 2 0 -2646 12 3000003.30 0 0 3 -1955 13 202000300 0 1 5 0 + 548 14 012201300 0 2 2 0 +I040 15 330212320 0 2 5 5 -3175 16 200020030 0 3 0 -1890 17 002200300 0 1 5 0 -1115 18 022221300 0 2 3 -2174 19 000200330 0 1 2 0 -3400 20 000200320 0 1 2 0 + 113 21 012301320 0 2 3 0 +I130 22 000300300 0 1 0 0 + 435 23 233020300 0 1 0 24 010321300 0 2 5 0 - 1985 25 511100220 0 .2 0 -1814 26 112111300 0 1 50 - 983 27 011211320 0 1 5 0 -1852 28 000100300 0 2 0 - 718 29 1 2 2 1 0 -2548 30 1111103200 1 5 0 31 000000000 0 0 0 -2c22 32 010010330 0 1 0 -22 1 1 33 3 34 023202300 0 2 3 0 35 3

ASSOCIATED VEIN MINERALS ; MINERALS WHICH ARE PRESENT ALONG WITH AU .AND Ag; 0 - ABSENT; 1 - MINOR; 2 - MODERATE; 3 - MAJOR; 5 - PRESENT TO UNKNOWN EXTENT. SH'TD ZONES ; OCCURENCE OF SHEETED ZONES ON THE VEIN: 0 - ABSENT: 2 - MINOR; 3 - MAJOR VEIN F0RM;LOCAL FEATURESOF THE VEINS; 1 - PLANAR & APPROX PARALLEL-SIDED; 2 - VARIABLE IN WIDTH & ATTITUDE; 3 - LENTICULAR; 4 - COMBINATION OF 2 & 3. TENL FEAT,TENSIONAL FEATURES,E.G.DIAGONAL GASH VEINS: 0 - ABSENT 2 - MINOR; 3 - MAJOR; 5 - PRESENT TO UNKNOWN EXTENT REPL,ASSOCIATED REPLACEMENT/ALTERATION: 0 - ABSENT; 2 - MINOR ; 3 - MAJOR; 5 - PRESENT TO UNKNOWN EXTENT DIST TO C0NTACT;DISTANCE FROMDEPOSIT TO NEAREST CONTACT BETWEENTHE ZEBALLOS STOCK AND COUNTRY ROCK(+,WITHIN THE STOCK; -,WITHIN THE COUNTRY ROCK).

301 FUTURE WRI:

We are in theprocess ofexamining the application ofa variety of multi- variate statistical methodsof evaluationto the Zeballos data fiLe. Among thesemethods aremultiple regression, discriminant function analysis,cluster analysis, andChaKaCteKiStiC analysis.These are complexmethods of dataevaluation that are hampered in thecase of Zeballosdata by thelimited number of depositsfor which dataare relativelycomplete.

Inaddition to statisticalevaluation of OUT quantitativedata file, a detailedstructural analysis appears to warrantattention to assist in defining aresource model forZeballos camp.

C~L[ISI~S

An extensivequantitative data file has been established for gold-quartz veins in Zeballosmining camp. A preliminaryevaluation of thesedata leads to thefollowing conclusions:

For pastproducers, total production in metrictonnes is an indicator of relativegross value of a deposit.

Largevein deposits are lower grade on averagethan are small vein deposits.

Gold and silveraverage grades appear highly Correlated on a log-log plotalthough this relationship appears to be accentuated by extreme hand sortingof small deposits.

A systematicrelation exists between gold grades andcombined copper pluslead content.

A pronouncedsystematic relationship exists between relative deposit worth(approximated by totalgold content) and distance from the nearestcontact of theZeballos stock. This relationship leads to a procedurefor defining areas of greatestpotential €OK gold-quartz veins in the camp.

A 1 000-metre-widezone centred on thecontact ofthe 7,eballos stock is an area ofhigh potential €OK location ofa depositequi- valentto the five largest producers known in the camp. A median targetdefined from the five producerscontains 900 000 grams of gold in 75 000 tonnes of ore.

ILcMKlwLJ3DQmms

This study,financed by theScience Council of 6ritish Columbia, is part of MINDP researchproject of theDepartment ofGeological Sciences, Universityof British Columbia, and is undertaken with thecooperation of

302 theMineral Resources Division, EZitish Columbia Ministry of Fnerqy, Minesand Petroleum Resources. Rchnical assistance has heen provided by Asger Bentzen.

Goldsmith, L. B., Sinclair, A. J., andRead, P. B. (inpreparation) : An Evaluation of Average Gradesand Production mnnaqes, Trout: Iake Mining Area, SouthernBritish Columbia. orr, J.F.w. andSinclair, A. J. (1971): A Computer-ProcwsableFile for MineralDeposits in the Slocanand Slocan City Areas of British Columbia, Western Miner, Vo1. 44, No. 4, pp. 22-34. Sinclair, A. J. (1979): PreliminaryEvaluation of Summary Production Statistics and bcation Data forvein Deposits, Slocan, AinswOKth andSlocan City Camps, Southern,8ritish Columbia, in Current Research,Pt. 8, Geol. .%rv., Canada, Paper 79-1B, pp. 173-178. Stevenson, J. S. (1950): Geologyand Mineral Deposits of theZeballos Mining Camp, B.C. Ministry of Energy, Mines & Pet. Res., Bull. 27, 145 pp.

303 304 AGE AND GENESIS OF CARIB00 GOLD I(IPERALIZATI0N DETERnINED BY ISO.r(PE lIETHoDS (93H)

BY meAndrew, C. I. Godwin, and A. J. Sinclair Departmentof Geological Sciences, me Universityof British Columbia

INTROD~IOW

The Caribooarea in southeasterncentral Rritish Co1umbj.a (Fig.107) is one of theoldest gold-producing regions in Canada (Sutherland mown, 1957).Gold-bearing quartz veins occur in Hadrynian to Cambrian meta- sedimentarystrata of the Cnnineca Belt. Triassicvolcanic strata in the adjacentIntermontane Belt alsohost quartz-gold veins. Galena-lead isotopedata were obtained from veins in bothterranes (Fig. 107) in ordertodetermine any geneticrelationship that might exist between them. Galena was alsocollected and analysedfrom stratiform and vein typemineralization in the MosquitoCreek Gold mine near Wells (Fig. 107, No. 427), toinvestigate thepossibility that at least some of the mineralizationthere might be syngenetic. K/Ar dates were obtainedfor muscovitefrom a quartz-baritevein associated with the Cariboo Gold Quartz mine, and forregionally metamorphosed phyllite.

Locations of galenaand K/Ar samplesare shown on Figure 107, and analysesare listed in Tables 1 and 2. Most ga1e.m samp1e:s were collected by D. Klepacki and R. Cook. MosquitoCreek ,and Cariboo Gold Quartzsamples were collected by theauthor, and Pin Money sampleswere collected by B. Price and C. I. Godwin. Most leadisotope analyses were by Q. D. Ryan. For these analysesgalena was dissolved in hydrochloric acid and thissolution was purifiedusing anion exchange columns and electrodeposition.Samples, loaded using the silica gel-phosphoric acid technique, were analysed on a 30-centimetre,solid sourl2e mass spectrometer inthe Department of Geophysics andRstronomy. Analyses of Pin Money, Cariboo Gold puartz and tbsquito Creek samples w,3re by A. Andrew who followedsimilar chemical separation and loadingte'zhniques but did theanalyses on a V. G. Micromass 54R mass spectrometer in theDepartment of GeologicalSciences. K/Ar dates were determined by J. Harak.aland K. Scott (see Table 2).

GE0Ux;Y

Triassicandesitic volcanic rocks of theIntermontane Belt arejuxtaposed againstProterozoic to Farly Paleozoicmetasedimentary strata of the Omineca Belt (Fig.107). The boundary is thoughtto be a low-angle, southwesterlydipping thrust fault (Klepacki, persona:l communication, 1981;Fees, 1981) , East of this boundarythe Protero::oic toCambrian Kaza andCariboo Groups are made up of conglomerates,ark.osic and quartz- osesandstones, shales and carbonaterocks (Campbell, et al., 1972;

305 1972). The Snowshoe Formation(Sutherland Brown, 1963) is equivalentto the Kaza Group (Campbell, et dl., 1972;Struik, 1981a). KazaGroup and Cariboo Group rocksare overlain unconformably by rocks of theBlack Stuart Formation,which aredark argillites and chert and dolomite brecciaswith bwer Devonian fossilstheirat base (Campbell, et dl., 1972;Struik, 1979). Mississippian volcanic andsedimentary rocks of the Cuyet Formationunconformably overliethe Black Stuart Formation.Several minor ankeritic, acidic dykes of pre-Mississippian ageintrude the Cariboo Groupand are known asthe Proserpine dykes (Sutherland Brown, 1957).

West ofthe boundary, Wiassic volcanicstrata of theIntermontane Belt arepredominantly andesitic andhave been interpreted arc-typeas volcanicrocks (Monger, et dl., 1972).Several intrusions occur within thisbelt, andmost have Jurassic K/M agesof approximately 180 Ma. me Cariboo Bell and Mitchell Bay porphyrydeposits also have 180 Ma K/?u agesand are auriferous (Hodgson, et dl., 1976;Schink, 1974).

Quartz-goldveins that occur within the Snowshoe Formationcontain galena,sphalerite, free gold,scheelite, and locallypyrrhotite or arsenopyrite. All theseveins contain important values in silver. Veins thatoccur in theTriassic strata differ in thatthey lack scheelite and sphalerite; sulphideminerals are mainly galena and chalcopyrite.

CARIB00 GOLD QUARTZ VEINS

OMiNECA BELT METASEDIMENTARY ROCKS

INTERMONTANE

TRIASSIC VOLCANICS

Figure 107. Locationsof gold deposlts trom whlch gaien&iead isotope analyses were obtained(refer to Table 1 fordeposit names). K/Ar analyses *re obtained frma veinand phyi lite near CG. The I ine dividing the Omlnecaand intermontane bits is probably a generallywestdipping thrust. C Is CaribxBeii porphyrydeposlt, andM Is Mltcheii Bayporphyry deposlt.

3 06 LEAD IS-E DATA

Lead-leadplots of thedata (Table 1) fromeach of thedeposits (Fig. 107)are shown on Figure 108. "he Cmnineca Belt data forms a singlegroup (Cluster 1) , which plots abovebut close to the 'shale curve' of tadwin andSinclair (1982), but markedly above the average crustal curve of Stacey andKramers (1975);both o€ these model curvesare shown €or reference on Figure 108. Data from stratiformmineralization atthe MosquitoCreek mine plot within Cluster 1.

Vein leads from Triassicvolcanic rocks are less radiogenicthan those of the Cmnineca Belt, plotting belowthe 'shale curve' on Figure 108. nus theyare distinctly different from Cluster 1. 15.8 - .- / \ A CLUSTER 1 / 426 ' 427CC \ ,427-pi Akv1 15.75 '

.. .. 18.6 18.8 19.0 19.2 206Pb/204Pb

Figure 108. 207Pb/20+bversus 206pb/204b plot of galenaanalyses frm Carlbooand adjacent InternontaneBelt gold deposits, (Table 1). Swbols are the same asthose of Flyre 107.

307 DISCUSSIOW

Coincidenceof Cluster 1 (Figs. 108 and 109) with the'shale curve' model suggeststhat a modelage can be givento the goldmineralization event. Ifthe 'shale curve' model applies, it also implies thatthe source of thelead, and by inferencegold, is upper crustal, since the'shale curve' represents leadevolution in a sialic, upper crustal environment (Gcdwinand Sinclair, 1982) .

30.4

30.2 .

CG-avg 0.3 \

39.0 .

MR tE 0 0 a\ 38.8 . a" 8 Fractionation 01 Slope f f 204Pb error Y 38.4 I I CD 18.8 18.8 19.0 18.8 18.8 . 19.2

Flyre 109. 20+b/20dpb versus 206pb/20dpb plot of galenaanalyses frmCarlboo and adjacent Intermontane Belt gold deposlts (Table 1). Syrnbols are the same as those of Flyre 107.

3 08 Justificationfor using the 'shale curve' model in this;part of the Omineca Belt comesfrom four lines of evidence:

Lead data from Sullivan, which is in thesouthern Cnnineca Belt, were used in the construction of thecurve. Similarities in thegeology of the Barkerville-Cariboo River area withthe Selwyn basin and Cassiarplatform ofnorthern British Columbiaand the Yukon havebeen noted (Struik, 19811s). Therefore althoughmost of thelead data used in theconstruction ofthe 'shalecurve' werefrom the Selwyn basin, Cmineca Belt leadshould have similarcharacteristics. fie provenanceof sedimentary rocks in the Omineca Belt is essenti- allythe same asfor those in the Selwyn shalebasin, since they are bothautochthonous terranes whichformed atthe western 1nargi.n of theNorth American craton.Therefore similar geochemical and iso- topiccharacteristics are to be expectedfor the Selwyn basin and Omineca Belt. Strataboundcarbonate-hosted deposits from theCarj.boo area also havelead isotopic compositions which fall on the'shale curve', givingages which agree with the Cambrianage of theirhost rocks. These deposits(Maeford Lake and Cornin Zhro' Bear),,clearly epi- geneticas crosscutting bodies in carbonaterocks (Holbek, personal communication,19821, are probably only slightly your,ger than their hostrocks. Some epigeneticcarbonate-hosted deposits in the Yukon canapparently be datedwith the 'shale curve' model(Godwin, et a1 ., 1980).Therefore carbonate-hosted deposits also support the hypothesisthat the 'shale curve' model is generallyapplicable to the Omineca Belt.

The calculatedage for the gold mineralization event is 185 Ma according tothe 'shale curve' model, butthis is only accurate toapproximately 50 Ma (Godwinand Sinclair,1982). K/Ar dating of a regionally metamorphosed phyllitegives anage of 179k8 Ma (Table 2) which is inter- pretedas being the age of the latest metamorphism. This agrees with previousestimates for the age metamorphismof by Pigage (1977) and Wanless, et dl. (1965). Struik(1981b) suggests that metamorphism occurredduring the Middle Mesozoic Columbian orogeny. Similarity in metamorphicand mineralization ages suggest that the vei~~smay be syn- metamorphic, ratherthan magmatic in origin.

At leastthree phases ofveins are present in the Cariboo Gold Quartz mine, and notall vein phases are gold-bearing (F. Beacmann, ,personal communication,1981). Muscovite fromone quartz-baritevein yielded a K/Ar model ageof 141+5 Ma (Table 2), which is the samea!; agesobtained forpost-tectonic granodiorite plutons southeast of thearea (Pigage, 1977). Thus atleast one set of veins is post-tectonic and my be relateddistally to plutonic activity. Althoughnone are seen i:? the immediatearea of the mine, plutons may be presentat depth. Whether the veinsaresynmetamorphic magmaticor in origindoes not alterthe

309 conclusionthat mostof the leadand gold were derived from the host rocks,either by lateralsecretion during regional metamorphism(Boyle, 1979).or by hydrothermalactivity related to magmatism.

Lead isotopedata from stratiformmineralization at the MosquitoCreek Goldmine areindistinguishable from those of thequartz-gold veins of Cluster 1 (Figs.108 and 109). Since the Snowshoe Formation is Paleozoic orolder and themineralization is Mesozoic,the difference between syngenetic and epigeneticlead would be readilydistinguishable by lead isotopeanalyses. The leadfrom Wsquito Creek is clearlyepigenetic based on leadisotopic composition.

Lead isotopic characteristics ofquartz-gold veins in Triassic strata are distinctlydifferent fromthose of the Cmineca Eelt deposits(Figs. 108 and log), indicating a fundamentaldifference in thesource of lead (and perhapsgold) in thesetectonic belts. Markedly differentmineralogy supportsthe hypothesis that the two veintypes have lead sources which aredifferent andunrelated. Forexample, lithophiletungsten in scheelite-bearing veins in the Snowshoe Formationcould have been derived fromthe sialic host rocks; its absencefrom veins in the more mafic Intermontane Belt is to be expected on chemicalgrounds if theveins have a host rock source. Thus, the differencesin the lead isotopes can be attributedto growth of lead in different uraniumand thorium environments.Figure 110 shows data from thisstudy plotted withInsular Belt data from Andrew, et dl. (1982)to display the contrast between these threedifferent lead provinces. Intermontane Belt lead is more likelead from theInsular Belt thanlead in the Omineca Belt.

COMPARISON OF OMINECA AND INSULAR BELTS GALENA-LEAD ISOTOPE RATIOS 158 - 100 Ma?

16.7 - P 0. :5 I56 INSULAR BELT GOLD VEINS

DEPOSITS

155 18.0 18.5 180 (P.5 2oePb1209b

~l~~~I!@. Conparison ot onlneca,Insular, and lnternwntane Belt galena-leadIsotope ratios. Triangles represent InterrmntaneBeltdeposlts In Table 1. Errorbars on the t lve clusters shan mark standard devlatlon of the suite for each cluster. The two grwth curves shown arethe 'shale' curve (Todrin and Slnclalr, 1982). and theaverage CrWfaI Curve (Staceyand Kraners. 1975).

310 me ageof mineralization of the veins in the Intermontane Belt is not known, but is probablyJurassic, ca. 180 Ma, based on theplutonic andvolcanic activity related to auriferousporphyry de.posits in this part of theIntermontane Belt.

~LUSIOllS

Thedifference in isotopic composition veinsof in Hadrynian metasedimentary rocks and in Triassicvolcanic rocksprecludes derivation oflead fromthe same source,thus ruling out thepossitlility that the goldin the Cariboo area was derived from theIntermontane Belt. Similarityin lead isotopic composition of stratiformgalena from the MosquitoCreek deposit with galena from clearlyepigenetic quartz-gold veins in the Omineca Belt suggests that syngeneticmineralization is not present.

Lead isotope and K/Ar evidenceindicate that the age of mineralization of thehineca Belt quartz-goldveins is f-hsozoic. Locaticmof Cluster 1 (Figs.108, 109. and 110) near the 'shalecurve' model suqges ts thatthe leadand gold have an upper crustal, host-rock source. The process by which metals were mobilized from theirhost rocks into Ithe quartz-gold veins was probably by lateralsecretion during regional. metamorphism. Supportfor this theory comes fromcoincident metamorphic and mineralization ages, but the possibility that theveins are related to distantJurassic plutons is not ruledout completely.

A host-rocksoutce for the gold in quartz-gold veins in the Triassic! arc- volcanicrocks may explainthe unradiogenic nature of the! leadin these veins.

AcKuUn.mGnEtiTs

D. Klepackisuggested this study, and a visit to the area was arranqed by V. Hollister. F. Beamann kindlyprovided hospitality and acted as guide to thegeology of the Cariboo Gold Quartzproperty. Ihe staff at Mosiquito Creek mine provided a tour of the underground workings.

We thank B. D. Ryan forhis careful analyses ofour samples. Financial supportfor this study was generouslyprovided by Rio Tinto Canadian ExplorationLimited and the Uritish Columbia Ministry of: hergy, Mines andPetroleum Resources. Figures were drafted by J. Elewlands and E. Andrew. The senior authorreceived a GraduateStudent Fellowship bursary fromthe University ofEritish Columbia,which is gratefully acknowledged.

REpERgRcEs

Andrew, A., Godwin, C. I. and Sinclair, A. J. (1982): Preliminary Examination of theMetallogeny of Gold in the Insular Belt using LeadIsotope Analyses, B.C. Ministry of Energy,Mines 6 Pet. Res., GeologicalFieldwork, 1981, Paper 1982-1, pp. 202-217. Boyle, R. W. (1979): The geochemistry of Goldand Its Deposits,Geol. Surv.,Canada, Bull. 280,pp. 390-428.

Campbell, R. B., Mountjoy, E. W., and Young, F. G. (1972) : Geology of McBride Map-Area, British Columbia,Geol. Surv., Canada, Paper 72-35,96 pp.

Godwin, C. I., Sinclair, A. J., and Ryan, B. D. (1980) : Preliminary Interpretation ofLead Isotopes in Galena-Leadfrom British Columbia Mineral Deposits, B.C. Ministry of Energy,Mines & Pet. Res., GeologicalFieldwork, 1979, Paper 1980-1, pp. 171-177.

Godwin, C. I. and Sinclair, A. J. (1982):Average Lead Isotope Growth CurveforShale-Hosted Bad-Zinc Deposits, Canadian Cordillera, Econ. Geol., Vol. 77, pp.675-690. Hodgson, C. J., Biles, R. J., and Verzosa, R. S. (1976):Cariboo-Bell, in PorphyryDeposits of the CanadianCordillera, C.I.M. Special Vol. 15, pp. 388-398.

Monger, J.W.H., Souther, 3. G. and Gabrielse, M. (1972) : Evolution of theCanadian Cordillera: A PlateTectonic MDdel, Am. Jour. Sci., Vol. 272, pp.577-602.

Pigage, L. C. (1977): Rb/Sr Dates for GranodioriteIntrusions on the NortheastMargin of the Shuswap Wtamorphic Complex, Cariboo Mountains,British Columbia, Cdn. Jour. Earth Sci., Vol. 14, pp. 1690-1695. Rees, C. J. (1981): Western Margin of the Omineca Belt at Quesnel Lake, British Columbia, Currentin Research, Pt. A, Geol.Surv., Canada,Paper 81-1A,pp. 223-226. Schink, E. A. (1974):Geology ofthe Shiko Lake Stock, near Quesnel Lake,British Columbia, B.Sc. thesis,University of British Columbia,64 pp. Stacey, J. S. andKramers, J. D. (1975):Approximation of Terrestrial Lead IsotopeEvolution by a 1Llo-Stage Model, EarthPlanet. Sci. Lett., Vol. 26, pp.207-221. Struik, L. C. (1979):Stratigraphy and Structure ofthe Brkerville- Cariboo Area, CentralBritish Columbia, in CurrentResearch, Pt. B, Geol.Surv., Canada, Paper 79-1B, pp.33-38...... (1981a): Snowshoe Ebbrmation, CentralBritish Columbia, in Current Research, Pt. A, Geol.Surv., Canada, Paper 81-1A, pp. 213-216...... (1981bl: A Re-examination of the Type Area of the Devono- MississippianCariboo Orogeny, Central British Columbia, Cdn. Jour. Earth Sci., Vol.18, pp. 1767-1775. Sutherland Brown, A. (1957) : Geology of the Antler Creek Area, Cariboo District, British Columbia, B.C. Ministry of Energy,Mines & Pet. Res., Bull.38, 105 pp...... (1963):Geology of theCariboo River, British CBlumbia, B.C. Ministry of Energy,Mines & Pet. Res., Bull. 47, 69 pp.

31 2 Wanless, R. K., Stevens, R. D., Lachance, G. R., and Rimsaite, R.Y.H. (1965): Age Determinations and GeologicalStudies, Part 1 - Isotopic Ages,Rept. 5, Geol. mrv., Canada, Paper64-17 (Pt. 1) , 126 pp. White, W. H., Erickson, G. P., Northcote, K. E., Dirom, G. E.,, and Harakal, J. E. (1967) : IsotopicDating of the aic:honBatholith, British Columbia, Cdn. Jwr. Earth Sci., Vol. 4, pp.677-690.

31 3 -Z-

r 0 ... t9 a I :: CHROMITE IN ME HOUUT SIDNEY WILLIAUS NiE3, CENTRAL BRIT,ISH COURlB'IA (93W)

By P. J. Whittaker Departmentof Geology, CarletonUniversity

ItmmDucTIou

Fieldworkduring the summer of 1982 constitutesthe third

&4T SIDNEY WILLIAMS

PlNCHl MOUNTAIN TUARTLAKE

MURRAYRIDGE

VANDERHOOF

Fiwre- 111. Location ma0 of Plnchi Mountaln. Murray Ridge, and bunt Sidney . Wllllam.

31 5 316 PINCH1 HOUIiTAIY

Pinchimuntain is underlainpredominantly by harzburgitetectonitn? and, to a lesser extent, by dunite. Eirittle shear from movemerkt inthe ]?inchi fault zonehas developed an intense foliation resulting irk friable platy, greyish brown watheredsurfaces. Harzburgite tectonite is medium to coarse-grained,equigranular, and carries accessorychromj.te. Serpentin- ization is extreme, usually 80 per cent or more complete.

Duniteoccurs as deformedlayers and pods withinharzburgite tectonite and is alsocompletely serpentinized. Ductile passively folded dunite layers and irregularlyshaped dunite podssuggests movem(mt in a :still- hotenvironment, which could be theupper mantle (Fig. 1 l;!).

Chromite was observedin an irregularly shaped dunite I-, 100 lmetres wide.The chromite layer hasbeen openly folded and is about 30 centimetreslong and exhibits a pinch-and-swellstru(:ture up to 3 centimetresthick. Chromite in it is medium grained,subhedral to euhedral,and forms EO per cent of the layer.Bleached serpentine, greenishwhite in colour, forms the groundmass.In 50 .per cent ofthe chromite,individual grains are rimmedby 0.5 to1.0-millimetre-thick bleachedserpentine halos.

WUUT SIDlJEy WILLIAI(s

Detailed mapping on muntSidney Williams indicates a predominanceof harzburgitetectonite with minor dunite, orthopyroxenite, andsca.ttered chromite-chromititelayers in dunite. Ihe West Peakarea, northwest of andin fault contact with Mount Sidney Williams, consists ofmassive and layerednorite (Little, 1947) withdunitic dykes or schlieren.This gabbro may berelated to theultramafic massif as a st.ratigraphically higher componentof a dismembered ophiolite or it may havebeen emplaced along an active fault zoneduring obduction.

Layeredzones within the muntSidney Williams massif were mapped and haveroughly parallel orientation,north striking with vertical dip. Layering is rhythmicand is defined by alternatinglayers of harzburgite anddunite. In some cases one or more orthopyroxenitelayers occur, usuallywithin dunite layers. Disseminated chromite and chromitite layers, up to 2 centimetresthick, are hosted someby dunitelayers. Layeredzones up to 5 metres wide were mapped withharzburgite layers up to 1 metre, dunitelayers up to 25 centimetres,and orthopyroxenite layersup to 4 centimetresin thickness. In most cases layeredzones are planarwith sharply defined contacts. One layered zone exhibited a doublyplunging synformal structure with higher order small-scale folding concentratedinthe noses of thestructure (Fig. 113) . Thispassive foldingsuggests that ductiledeformation took place in z1mes withinthe ultramaficmassif.

317 ......

......

31 8 Severallayered chromitite occurrences were mapped; somB haveConsider- able lateral extent(about 500 metres). A vertical 2011e consistingof severaldunite layers, one of which carries a 0.5 to 2-centimetre-wide chromitite band,occurs 50 metres north of the summit of Mount Sidney Williams. Thislayer strikes north and is subparallel to the summit ridge. A similar zonewith a chromititelayer (Fig. 1'14) cropsout on the floor of a cirque 500 metres to thenorth and directly on strike with the summit chromi ti te occurrence.

Chromitein layered occurrences on Mount Sidney Willianls oftenexhibit bleachedgreenish white reaction rims. Theseserpentine-chlorite rims surroundmedium-grained subhedral toeuhedral chromite a.nd are 0.5 to 1 millimetres thick.Preliminary microprobe analyses show thechromite to be highlyaltered with high aluminum,magnesium, andsometimes hiqh iron compositions.Texturally thealtered chromite exhib:tts skele-tal to dendritic formwhich is made upof magnetite and lowchromium chromite or ferrichromite. In some grainsremnant unaltered cores ofchromite occur; these are irregularin formand have serratedborders. The chromite cores are amber toreddish brown intransmitted light andhave lower chromevalues than chromite from podiform chromitite described from the Mitchell Range (Whittaker, 1982a. 198213).

AcKuu?LmGnENTs

Financialsupport for fieldwork was receivedfrom the lhitish Columbia Ministry of Energy,Mines and PetroleumResources and the Geological Survey of Canada (Grant203/4/81) viagrants to Dr. D. H. Watkinson.

REPERENCES

Armstrong, J. E. (1949):Fort St. James Map-Area, Cassiar and Coast Districts, British Columbia, Geol. mrv., Canada, Nm. 252,210 pp. Little, H. W. (1947): me Ultrabasicand Pssociated Rocksof theMiddle River Range, BritishBlumbia, unpub. Ph.D. thesis,University of Toronto. Paterson, I. A. (1977): The Geologyand Evolutionof the Pinchi Fault Zone at PinchiLake, Central British Columbia, C,rln. Jour. .Garth Sci., Vol.14, pp. 1324-1342. Whittaker, P. J. (1982a):Chromite mcurrences inUltramafic rocks in theMitchell Range, CentralBritish Columbia, inCurrent Research, Pt. A., Geol. SVrv., Canada, Paper 82-1A. pp. 239-2415...... (1982b) : ChromiteOccurrences in Mitchell Flange Ultramafic Rocksof theStuart lake Belt, CacheCreek Group, B.C. Ministry of Energy,Mines & Pet. Res., Geological Fieldwolrk,1981, Paper 1982-1,pp. 234-243. Whittaker, P. J. andWatkinson, D. H. (1981):Chromite in Some Ultra- mafic Rocks of the CacheCreek Group, British Co1umb:ta. in Current Research,Pt. A, Geol. mrv., Canada,Paper 81-1A. pp. 349-355.

Queen's Pnntcr for British Columbia 0 victoria, 1983 319