Toodoggone Geoscience Partnership: Preliminary Bedrock Mapping Results from the Swannell Range: Finlay River – Toodoggone River Area (NTS 94E/2 and 7), North-Central British Columbia1

By L. Diakow, G. Nixon, B. Lane and R. Rhodes

KEYWORDS: P3, public-private partnership, Targeted Toodoggone River in the north and east (Fig. 1). The new Geoscience Initiative II (TGI-II), bedrock mapping, result s reporte d below em phasiz e changes in the Early Ju- stratigraphy, Finlay River, Toodoggone River airborne ras sic stra tig ra phy of the Toodoggone from west to east. gamma-ray spectrometric and magnetic survey, Toodoggone River, Finlay River, Toodoggone formation, Black Lake Intrusive Suite, Cu-Au porphyry, epithermal LITHOSTRATIGRAPHIC UNITS Au-Ag Over the past two field seasons, nearly 600 km2 of the INTRODUCTION Swannell Ranges, situ ated be tween the major drainages of the Toodoggone and Finlay rivers and their conflu ence , The Toodoggone Geoscience Part ner ship was ini tiated have been mapped in detai l, thereby refin ing Juras sic stra - in 2003 to gener ate detai led geoscience infor m ati on, in- tigra phy that was, for the most part, pre viously assigne d to clud ing air borne geo phys ics and bed rock ge ol ogy maps, an un di vided Hazelton Group map unit (Diakow et al., that would sup port min ing ex plo ra tion in pre vi ously ex- 1985, 1993). As a conse quence of mapping in 2004, a re - plored and more re mote ter rain in the east-cen tral gion of pre viously undi vided Juras sic rocks is now identi - Toodoggone River and McConnell Creek map ar eas, which fied as part of the Toodoggone form ati on. These rocks have are consid ered highly prospec tive for Cu-Au porphyry and been sub di vided in for mally into strati graphic mem bers, epi ther mal Au-Ag min er al iza tion. The suc cess of this part - which collec tively repre sent one of the most com plete nership is based on the parti ci pa ti on of all five mining com - Early Ju ras sic se quences ex posed any where in the panies acti vely explor ing the program area (Stealth Miner - Toodoggone River area. Vol canic rocks pre sumed to be als Ltd., Northgate Min er als Corp., Finlay Min er als Ltd., near the bottom of the Toodoggone form ati on rest uncon - Bishop Gold Inc. and Sa ble Resource s Ltd.), coupled with form ably on ei ther volca nic strata of the Late Tri as sic Takla per son nel from the British Co lum bia Geo log i cal Sur vey, Group or granitoid rocks of the Early Juras sic Black Lake the Geological Survey of Canada and the University of Intru sive Suite. The oldest rocks consis t of bedded sedi - British Columbia. men tary strata of the Up per Pa leo zoic Asitka Group; these In 2004, the Geolog i cal Survey of Can ada re leased are gener all y poorly ex posed, local ly intrude d and ther- digi tal data and a serie s of maps from a low-level, high-res- mally al tered by Juras sic intru sions , and rarely observe d to o lu tion air borne gamma-ray spec tro met ric and mag netic be overlai n disconformably by the Takla Group. survey that covered 1) most of the known porphyry and epi - The gener al ize d geol ogy of the study area is shown in ther mal tar gets within the main area of pro spec tive Early Fig ures 2 and 3, and repre sen ta ti ve stratigraphi c secti ons Juras sic rocks; and 2) a re mote and rel ati vely under- are given in Fig ure 4. The stra tigra phy is transected by ma- explored region farther east in the Swannell Ranges of the jor northerl y to north-northwest erly-trending high-angle Toodoggone area (Shives et al., 2004). faults, no ta bly the Pil lar and Black faults, in ter sected by Bed rock map ping con tin ued in 2004, ex pand ing the easterl y to northeas terl y-trending cross-faults (Fig. 2). East area of detai led 1:20 000-scale map cover age in two re - of the Pillar Fault, the stra tig ra phy is con sis tently in clined gions: 1) the southern region, locat ed 55 km southeas t of to the west-southwest and has rel ati vely shal low dips (15– the Kemess South Cu-Au porphyry mine and cen tred on 25°). Johanson Lake (Schiarizza, 2004a, b; Schiarizza and Tan, this volum e); and 2) the northern region, be tween the Asitka Group (Unit PAs) Toodoggone and Finlay rivers (Diakow, 2004). This paper sum ma rizes the re sults of geo log i cal map ping con ducted in The Pennsyl vanian to Early Perm ian Asitka Group a 250 km2 area lo cated east of the Pillar Fault (Diakow, com prises several large pendants rest ing on or adja cent to 2004) and bounded by the Finlay River in the south and the the Early Juras sic Duncan pluton near Drybrough Peak (west of the study area), where both vol canic and stratigraphically higher sed im en tary rocks were mapped 1Contribution of the Federal-Provincial Targeted Geoscience pre vi ously (Diakow, 2004). In this study, scatter ed out- Initiative-II (TGI-II) crops of the Asitka Group were encoun ter ed near the

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1 A Bedrock Mapping Studies L N I Pine 2005 proposed mapping F Diakow et al., this study Diakow, 2004 Diakow, 2001 Diakow et al., 1993 and 1985 1:20000 Mapping 0 2 4 Schiarizza, 2004 and Schiarizza and Tan, this volume Active Mining Properties kilometers Legun, 2001 MINFILE Occurrence Monger, 1977 Eisbacher, 1974 Provincial Park

Fig ure 1. Lo ca tion of bed rock map ping completed in 2004. In set on the left shows published geo log i cal work in the Toodoggone River (94E) and McConnell Creek (94D) map ar eas (see ref er ences). treeline in an area east of Jock Creek (Fig. 2). Here, the suc - phyric ba salt flow that over lies siltstones consid ered to rep- ces sion is about 130 m thick and intrude d by an Early Juras - resent part of the under ly ing Asitka Group. This contac t is sic quartz monzonite stock at the lower contac t. Limestone in ter preted as a disconformity, al though there is little ev i - ad ja cent to the in tru sive con tact is recrystallized and re - dence of erosion. Above this contac t, lavas more typi cal of placed lo cally by ir reg u lar zones of di op side-gar net-mag- the Takla Group predom inate , and include a vari ety of por- ne tite skarn, and car ries patchy ga lena and chalco py rite phy ritic bas alts contai ning abundant, medium to coarse min er aliza tion. Higher in the sec tion, pale grey weath ered (<6 mm) pheno crysts of clinopyroxene. Other, volu m etri - limeston e al ter nates with whitish chert in beds varying cally mi nor flow va ri et ies in clude dis tinc tive por phy ritic from 10 to 50 cm thick. Above the highest chert lay ers, lavas with bladed-plagioclase texture s and aphani ti c bas- siltstone inter leaved with thin black mudstone part ings oc - alts. Pyroxene-bearing sand stones occur as sparse, thin cupies the upper m ost 20 m of the sec tion. The upper m ost interbeds within the volcanic succession. sedi m entar y strata are sharply overlain by pyroxene- bearing lavas of the Late Triassic Takla Group. Basal Toodoggone Formation Unconformity Takla Group (Unit uTTv) Bed ded polymictic con glom er ates and sand stones The Late Tri as sic Takla Group is exposed along the (unit Tc1) occur at a num ber of isolat ed local iti es in the lower north- and east-facing slopes of the mountai ns south south ern Toodoggone map area, and oc cupy the in ter val of Jock Creek, and in nearby outcrops where it is juxta - be tween mafic vol canic rocks of the Takla Group and over- posed against the Toodoggone form ati on by high-angle ly ing quartz-bi o tite-bear ing vol ca nic rocks of the faults. South of Jock Creek, the lower contac t of the Takla Toodoggone form ati on. These depos it s mark a basal un - Group is marked by an unusu all y coarse clinopyroxe ne- conform ity of re gional extent in the Juras sic succes sion,

94 Brit ish Co lum bia Geo log i cal Sur vey and record vari able upli ft and inci sion deep into pre- abun dant ba salt to an de site por phy ritic flows con tain ing Jurassic strata and exhumed plutons. clinopyroxene, flow-lam inate d dacite to rhyo li te lavas, and The basal comglomeratic de pos its may be traced dis- a gener all y greater propor ti on of volcaniclastic rocks of conti nu ously for al most 7 km west of the Pil lar Fault south var i ous or i gins. Un like most of the Toodoggone for ma tion, of Jock Creek (Diakow, 2004), and have been found farther quartz and bi oti te pheno crysts are rarely ob served in these east at two iso lated lo cal ities in the study area. The con- youn ger rocks. glom er ates gener all y consis t of sand-granule matri x- to DUNCAN MEMBER (UNIT TD) clast-supporte d rounded cobbles and boulders de rived from Takla, granitoid and, less com monly, Asitka sources. The Duncan mem ber is well exposed in the southeas t- At one local ity not visit ed by the authors, but portra yed ern part of the study area betwee n the Finlay River and Jock sche mat i cally in sec tion 1 of Fig ure 4, a mining com pany Creek. It comprises a thick, crudely layered succes sion of re ported con glom er ate dom i nated by granitoid de bris rest - pre dom i nantly nonwelded, dacitic lithic-crys tal tuffs ing atop an early quartz monzonite phase of the com posit e interbedded with minor crystal -rich volca nic sandstone and Jock Creek pluton (Fig. 2; de scribed below). At the second siltstone. The base of the succes sion is marked local ly by local ity, the uncon form ity is marked by a thin (<7 m) suc- quartz-bear ing sand stones in gradational contac t with con- ces sion of basal, cobble to pebble con glom er ates pass ing glom erati c beds that mark the basal uncon form ity of upwards into coarse to medium -grained, feldspathic to Toodoggone strata on the Takla Group. Elsewhere, how- lithic sand stones con tain ing de tri tal quartz. ever, incipiently to moder ate ly welded ash-flow tuffs rest direct ly on erosiona l rem nants of the Takla Group. Here, Early Jurassic Toodoggone formation within a few metres of the contac t, the plane of welding is more steeply inclined (>50°) and re flects the lo cal attitude The Toodoggone form ati on is an exclu sive ly subaerial of the rugged paleosurface. vol ca nic suc ces sion that com prises the sole sub di vi sion of The lithic com ponent (<10 vol. %; <3 cm across) of the the Early Ju ras sic Hazelton Group in the Toodoggone River pyroclastic beds consti tutes subrounded to subangular area. Togethe r with cogenetic plutons of the Black Lake In- clasts of finely por phyritic to apha ni tic andesitic vol ca nic trusive Suite, these rocks host im portant Au-bearing epi - rocks. The crystal com ponent (typi cal ly 1–3 mm) is dom i- ther mal and por phyry-style min eral de pos its. Map ping of nated by broken plagioclase accom panied by minor to trace the Toodoggone for ma tion has oc curred ep i sod i cally over amounts of rounded (resorbed) quartz and oxi dize d, cop- sev eral de cades re sult ing in an evolv ing in ter nal stra tig ra- pery flakes of bi oti te. phy. A num ber of in for mal mem bers have been proposed South of the study area in the vi cinit y of the Kemess for local ly mappable lithological units whose depositional North Cu-Au porphyry occur rence , pyroclastic flow de- ages are reason ably well constra ined by more than 20 isoto - pos its dom i nate sec tions un con form ably over ly ing the Tri- pic ages (Diakow, un pub lished data). as sic vol ca nic rocks. A sim i lar re la tion ship is also ob served Strati graphic mem bers of the Toodoggone for ma tion south of Attycelley Creek, where nonwelded to incipiently exposed in the region betwee n the Finlay and Toodoggone welded tuffs over lie nearly 100 m of lay ered epiclastic rivers include the Duncan, Metasantan and Saunders mem - rocks above the basal uncon form ity. At both local iti es, U- bers, all of which have widesprea d distri buti on west of the Pb isoto pic dates deter mined for pyroclastic rocks assigne d Pil lar Fault (Diakow, 2004). In places, rocks of the Duncan to the Duncan mem ber are pre cisely estab lished at 199 to mem ber are ob served over ly ing Up per Tri as sic strata 200 Ma. above a basal uncon form ity marked by erosion and typi fie d by bedded epiclastic rocks. East of the Pillar Fault and north METSANTAN MEMBER (UNIT TM) of Jock Creek, new strati gra phy is rec ognize d rest ing upon The Metsantan mem ber occu pies much of the ter rain vol ca nic rocks that re sem ble the Metsantan mem ber. We in - north of the Finlay River, extend ing to the vi cinit y of The clude these new rock units as part of the Toodoggone for - Pil lar, where it is trun cated by west erly-trending faults, and mati on and, in order of as cending stratigraphi c posi ti on, in - east of Mt. Graves to the Toodoggone River. The unit com - for mally name them the Quartz Lake, Graves and Pillar prises a fairly hom oge neous suc ces sion of andesitic lavas, mem bers. To the west, ad ja cent to Saunders Creek, the in clud ing as so ci ated flow brec cias, minor interbedded lower part of this new succes sion, ten tatively cor re lated epiclastic and rare pyroclastic rocks. The basal con tact with with the Quartz Lake mem ber, forms sev eral out liers, with the Duncan mem ber is abrupt and gener all y marked by one secti on rest ing uncon form ably on rocks of the massive flow se quences largely devoid of layer ing or Saunders mem ber (western extre m ity of Fig. 2). This rela - internal flow features. tionship indi cat es that the new stra tigra phy is younger than Lavas of the Metsantan mem ber typ i cally con tain the Saunders mem ber, and a new U-Pb date from the study equant to subequant, blocky plagioclase pheno crysts (usu- area confirm s that these rocks be long in the upper part of ally 3–5 mm), rarely found in glomeroporphyritic inter- the Toodoggone for ma tion. growth (<8 mm), that com monly form 15–25 vol. % of the Typi cal ly, rocks of the Toodoggone form ati on have a rock. Mafic pheno crysts in clude variably al tered, pris matic narrow compositional range be tween high-silica ande sit e hornblende and euhedral bio ti te (<5 mm) and gener all y and dacite, and contai n vary ing amounts of di agnos ti c consti tute less than 5 vol. % of the rock. Unusu all y bi oti te- quartz, bi oti te, hornblende and apa ti te pheno crysts. The rich (8–10 vol. %) an de site lavas are compar atively rare new stra tig ra phy, how ever, is dis tin guished by lo cally though well exposed, for exam ple, on a westerl y-trending

Geo log i cal Field work 2004, Pa per 2005-1 95 ridge just south of The Pil lar. Acces sory miner als include Metsantan andesites cover an exten sive part of the small (<1 mm) grains of resorbed quartz and reddish apa ti te Toodoggone region and rest on ash-flow tuff succes sions prisms (<1 mm) which, though de fini ti ve of these lavas, are that appear to have slightly dif ferent ages. Ar gon-ar gon sparsely distri buted. Based on phenocryst miner al ogy and dating of this flow sequence has been hindered by the pau - chem i cal com po si tion, these rocks are com monly re ferred city of fresh hornblende and bi oti te. However , the two Ar- to as trachyandesite or high-silica an de site. Ar dates that have been obtai ned yield sim ilar isoto pic ages East of the Black Fault in the area between the Sickle of approx i m ately 196 and 194 Ma. Creek and Quartz Lake cirques, andesitic flows are SAUNDERS MEMBER (UNIT TS) interbedded with, or overlai n by, well-sorted sand stones and cobble to pebble con glom er ates with rounded clasts of The Saunders mem ber is a hom oge neous dacitic ash- por phy ritic to apha ni tic andesites and monzonitic granitoid flow tuff sequence best exposed in the region west of rocks. These beds are tenta ti vely include d within the Saunders Creek and northwest toward the Toodoggone Metsantan mem ber, al though some of these clastic se- River (Diakow, 2004). Other thick accu m ula ti ons are quences may be long to the overly ing Quartz Lake mem ber found south of the Finlay River and northeas t of the (descri bed below) due to fault repe ti tion (Fig. 5). Kemess South mine (Diakow, 2001). South of Jock Creek,

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a 4 º n ll º 7 i F i 6 2 kilometres 2 1 1 Fig ure 2. Gener al ized geol ogy of the study area east of the Pillar Fault between the Finlay and Toodoggone rivers. Num bered transects lo- cate the strati graphic sec tions shown in Fig. 4. In for mally named lakes and a creek ref er enced in the text are also in di cated. The dash-dou - ble dot con tact be tween early and late phases of the Jock Creek pluton is in ferred from the aero magnet ic data of Shives et al. (2004).

96 Brit ish Co lum bia Geo log i cal Sur vey an iso lated oc cur rence of red dish ox i dized pyroclastic Seven Ar-Ar and U-Pb isoto pic dates indi cat e that the flows form a cap less than 70 m thick on a ridge that, at Saunders mem ber erupted during a brief inter val be tween lower alti tude, exposes lavas of the Metsantan mem ber. 194 and 193 Ma (Diakow, un pub lished data). The highly vari able thickness of the Saunders unit is attri b - uted to the in flu ence of pre-ex ist ing to pog ra phy and synvolcanic faults. New Rock Units Forming the Uppermost Toodoggone Formation

Dacite ash-flow tuffs of the Saunders mem ber are East of the Pil lar Fault, a previ ously undi vided succes - some of the least altered rocks in the Toodoggone area. sion of lavas and interbedded, well-strat ifie d pyroclastic- These rocks ex hibit a char acter istic grey color and, be cause epiclastic rocks forms a gentl e west-southwest -dipping of their indurated char acter , gen er ally form a resis tant homocline. Epiclastic strata near the base of this suc ces sion stratigrap hic marker. The tuffs are no ticeably en riched in near an in for mally named lake, Quartz Lake, over lie broken crystal s of plagioclase (up to 40 vol. %). Splendant hornblende- and/or bi o tite-bear ing an de site flows pro vi- crystal s of hornblende (up to 7 vol. %) and lesser bio ti te and sionall y as signed to the Metsantan mem ber (sec tion 5 in quartz (trace to 3 vol. %) make up the major it y of the re- Fig. 4 and Fig. 5). Since the Saunders mem ber is appar entl y maining crystal popu la ti on. Dark grey to black, cognate missing in this area, this con tact is in ter preted as a vitrophyre fragm ents (5–45% of the rock) oc cur through- disconformity. El em ents of the new strati gra phy , however , out the ash-flow de posit and local ly becom e densely dem onstra bly overli e the Saunders mem ber west of the Pil- welded to define a pronounced eutaxitic texture . Although lar Fault, where epiclastic rocks mark an ero sional con tact. this unit is com monly oxi dize d to reddish hues, the prim ary From these rela ti onships and a new U-Pb date derive d from miner al ogy and vitrophyric texture s are readily identi fi- near the middle of the new sequence , it is evi dent that these able. rocks are time strati graphic, in part, with dated strata in the

Hazelton Group (Early Jurassic) Toodoggone Formation Toodoggone Formation (continued) Pillar member Metsantan member Andesite and scarce flow-laminated dacitic flows Andesite lavas containing hornblende, biotite and TPv2 TM rare quartz; scarce bedded sandstone and conglomerate

Bedded crystal-lithic tuff, lapilli tuff, interlayered with Duncan member TPs2 volcanic-derived tuffaceous sandstone and conglomerate accretionary lapilli tuff Dacite crystal and lithic tuff containing trace quartz and biotite; TD minor bedded sandstone

Basaltic andesite to andesite lavas containing clinopyroxene TPv1 phenocrysts Basal conglomerate Polymictic conglomerate containing granitoid and Takla Bedded crystal-lithic tuff, tuff breccia; pyroxene-bearing Tc1 volcanic clasts volcanic sandstone, siltstone and lesser conglomerate TPs1 granitoid accessory fragments in lapilli tuff accretionary lapilli tuff Takla Group (Early Triassic) Graves member Dacitic ash-flow tuff; incipient to local moderate welding; TG diagnostic pink rhyodacite fragments uTTv Basaltic lavas, plagioclase and/or clinopyroxene phyric; accidental granitoid fragments; rare to locally abundant local pyroxene-rich sandstone Quartz Lake member Asitka Group (Late Carboniferous - Early Permian) Rhyolitic lavas; flow laminated; local spherulitic TQr devitrification PAs Limestone, chert, minor black mudstone TQt Rhyolitic crystal-vitric tuff; bedded Black Lake Intrusive Suite (Early Jurassic) __ Basalt to andesite lava and associated flow breccia _ _ _ _ X TQv and tuff; minor interbedded epiclastic deposits _ Quartz monzonite(qm) and porphyritic monzonite(mp) _ _ B ___ X Volcanic sandstone, pebble/cobble and locally + TQs boulder conglomerate; poor to moderate sorting; + hematite stained; minor tuff +B+ Jock Creek pluton: early(qm1) and late(qm2) quartz monzonite + + Saunders member Dacite ash-flow tuff containing hornblende and biotite d Medium to coarse-grained diorite; clinopyroxene and TS phenocrysts; moderately to strongly welded with locally B biotite-bearing distinctive fiamme

Fig ure 3. Leg end to ge ol ogy map in Fig ure 2 (op posite page). Addi tional strati graphic el e ments and unit de scrip tions re fer to sec tions shown in Figure 4.

Geo log i cal Field work 2004, Pa per 2005-1 97

SE The Pillar - Mt. Graves NW 7

Finlay River - Jock Creek TPv2 (composite stratigraphy) TPs2 J

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C1 u T U-Pb TQs TG l t Bqm1 192.3+0.4 Ma + TQv (Ar-Ar) + + TQs + TG TG + TQv + U V + + TT TM TQs + TQv + 100m + TQv + (Ar-Ar) TM TQr 100m + PAS + TM + (U-Pb) _ + + _

+ Bqm2 (U-Pb) _ _ + Bqm _ 0 + + _ _ Bqm1+ + 0 Vertical Scale Vertical Scale (sections 1 - 2) Conformable contact U-Pb zircon date (in progress) (sections 3 - 8) Contact unknown Ar-Ar biotite/hornblende date (in progress) Unconformity Epithermal veins - Au, Ag, Pb, Zn Fault Skarn - Cu Fig ure 4. Gen er al ized com posite sec tions showing lithostratigraphic sub di vi sions for rocks east of the Pil lar Fault, be tween the Finlay River and Toodoggone River. Lo ca tion of sec tions are shown on Figure 2 and de scrip tions of map units are given in Figure 3. upper part of the Toodoggone formation residing outside faulted, are well exposed in the cirque headwall and ridges the map area. surround ing Quartz Lake (Fig. 5). The mappable units The vol canic rocks in this package are compositionally shown in Fig ures 2 to 5 are des ignate d accord ing to their di verse, com pris ing bas alts and andesites dis tin guished by lithological char ac ter is tics rather than their ex act strati- the presence of clinopyroxene, and apha niti c to sparsely graphic context , which in many cases is not ade quate ly porphy rit ic rhyodacite and rhy oli te that repre sent the most known; thus, these units may oc cupy dif ferent strati graphic dif fer en ti ated rocks in the en tire Toodoggone area. Other hori zons within the Quartz Lake member. dis tin guish ing fea tures of the new stra tig ra phy in clude the At Quartz Lake, a basal coarse clastic de posit (TQs) nota bly reduced (trace) abundance of quartz, bi oti te and ap- over lies bi o tite-bear ing andesitic lavas of the Metsantan ati te in the flows and pyroclastic rocks, and the much higher mem ber. This dark reddish brown to maroon, poorly sorted pro por tion of vol ca nic-de rived sed i men tary rocks com- deposit contai ns angu lar to rounded, pebble- to boul der- pared to other parts of the Toodoggone area. size (<5–30 cm) clasts of apha niti c to por phyrit ic The homoclinal succes sion de scribed above is esti - Metsantan volca nic rocks in a fine to medium -grained mated to be about 1 km thick in the area betwee n Quartz sandy ma trix lo cally con tain ing bi o tite crys tals (<2 mm). Lake, Mt. Graves and The Pillar . The rocks are subdi vided This basal unit proba bly repre sent s a wa ter-washed laharic in for mally into the Quartz Lake, Graves and Pillar mem - brec cia; how ever, this bed may also in clude weath ered flow bers, listed in or der of as cending stratigraphi c posi ti on breccia . This deposit is sepa rat ed from overly ing dark red- within the Toodoggone form ati on, begin ning at the top of dish brown, moder ate ly sorted, medium to coarse-grained the Saunders mem ber. Re lati onships betwee n the new stra - vol ca nic sand stones (also TQs) by minor faulting and rhyo - tig ra phy and older rocks are de picted in the ref er ence sec - lite intru sion (Fig. 5). These beds in turn are overlai n by the tions shown in Fig ure 4. basal part of the Graves ash-flow tuff mem ber (de scribed below), which contai ns diag nos ti c pink dacitic fragm ents QUARTZ LAKE MEMBER (UNITS TQS, TQV, (<4 cm) and broken plagioclase crystal s (<2 mm) and, at TQR, TQT) this lo cal ity, hosts an ex ten sive quartz±adu laria–cal cite– As noted above, the Quartz Lake mem ber is a heter o - (?)barit e stockwork with traces of sul phide miner al iza tion. geneous lithostratigraphic unit com prising interbedded In the cirque wall west of Quartz Lake, a thin se quence of volca nic and volcaniclastic rocks that, although complexl y fine to medium (1–3 mm) plagioclase-phyric, pyroxene-

98 Brit ish Co lum bia Geo log i cal Sur vey bear ing an de site flows (TQv, best de vel oped elsewher e) dark grey to red, finely porphy rit ic (<1.5 mm) plagioclase- are found at or near the hematitic base of this pre dom inantl y phyric ba saltic andesites with small amounts (<3 vol. %) of clastic unit (Fig. 5 and Fig. 4, sec tion 5). clinopyroxene; how ever, augite-rich vari ants (10–15 vol. %; <5 mm) and strongly amygda loi dal flows carry ing Other exposures of unit TQs, for exam ple, are found subequant clinopyroxene megacrysts (<1 cm) are local ly approx i m ately 4 km due west of Quartz Lake below the con spic u ous. faulted base of the Graves mem ber, in scat tered outcrop s along the western lower slopes of a broad val ley to the At The Pil lar, well-strat ified se quences of volca nic north west of the lat ter lo cal ity and in the vi cin ity of The Pil - con glom er ates, sand stones, siltstones, ash-flow tuffs and lar (Fig. 2). At the for mer lo cal ity, these well-strat ified , tuffaceous brec cias (TQs) un der lie rhyolitic tuffs and lavas epiclastic and pyroclastic rocks are in ter calated with vari- (TQr) rest ing di rectly be low the Graves mem ber. Simi lar ably por phyritic ba saltic to andesitic lavas (TQv). The sed i- rhyolitic rocks oc cur 3 km northeas t of The Pil lar and form mentar y rocks include buff to reddish brown weather ing, small out liers at the top of cirque headwalls above Griz waterlain vol ca nic brec cias, volca nic cobble to boulder Lake and Sickle Creek (Fig. 4 and 5). Dark red to pale grey- con glom er ates local ly enclos ing large (up to 50 cm across) green, spherulitic rhyo li te lavas com monly exhibi t flow rounded monzonitic clasts, and coarse sand stones. lamina ti ons and contai n plagioclase (<20 vol. %) and bi o - Pyroclastic interbeds are dom inate d by grey-green lithic- tite (3 vol. %) pheno crysts. Thickly bedded se quences (<30 crys tal ash-flow tuffs of dacitic com posi ti on and their re - m) of vitric-crys tal rhyo lite tuff with sparse lithic frag ments worked equiv alents. The as so ciated lavas are com monly (<2 cm) lo cally un der lie the rhy o lite flows.

Tb TMs?

TMs

TMs

r QQuuaarrttzz LLaakkee < 570 A-E TPs1 QQuuaarrttzz LLaakkee r

< S GGrriiizz LLaakkee TPs1 TQr 0 1

Kilometre

Fig ure 5. Ge ol ogy of the Quartz Lake–Griz Lake area, showing stratigraphic el ements of the Toodoggone for ma tion not rep re sented in Figure 2: the lo ca tion of rhy olite sills and dikes (r); and epi ther mal quartz-sul phide veins (570A-E) and stockworks (S) of the Sickle-Griz showing. The stra tig ra phy dips 20–30° de grees to the west-south west and map units are those of Figure 3, except for epiclastic beds within the Metsantan mem ber (TMs) and a ba saltic sill (Tb). The heavy dot-dash line repre sents volcaniclastic and/or vol ca nic se quences too thin to show at map scale.

Geo log i cal Field work 2004, Pa per 2005-1 99 Exten sive expo sures of basal tic and andesitic lavas monzonite and quartz monzonite are sparsely distri buted, (TQv) are found on the valley slopes and ridges north and parti cu lar ly in the upper part of the ash-flow sequence . south of Mt. Graves (Fig. 2). Some flows are finely porphy - Their subrounded to rounded shapes suggest that these ritic, carry ing plagioclase (<1.5 mm; up to 15–20 vol. %) clasts were likely de rived from subaerial drainages and in- and clinopyroxene (<1 mm; 1–3 vol. %). Other lavas are corpo rat ed during the pas sage of the pyroclastic flows. more dis tinctly por phy ritic, car ry ing euhedral pheno crysts Frag ments of plagioclase (<2 mm) dom inate the crys tal of clinopyroxene (<4 mm; 10–15 vol. %) and subequant fracti on of the matri x, local ly accom panied by sparse plagioclase (<3 mm with rare glomerocrysts up to 7 mm; up quartz and/or bio ti te grains. to 20 vol. %). Rarely, flows and/or near-surface dikes are The Graves mem ber is well indurated and, although it encoun ter ed with euhedral megacrysts (<1.5 cm) of has the gen eral ap pear ance of a nonwelded single cooling clinopyroxene (<5 vol. %) rarely ac com panied by unit, was proba bly emplaced as multi ple flow units. Lo - subequant plagioclase (<3 vol. %). Minor interbeds of vol- cally, lithic-rich tuffs at the top of this unit appear to have ca nic brec cias of diverse ori gins are found local ly, includ - been re worked to some degree. Incip i ent to moder ate weld - ing monomictic laharic brec cias with poorly sorted volca - ing is observe d in places and indi cat ed by flattene d reddish nic clasts (<33 cm). It is in ter est ing to note the rad i cal brown to dark green fiamme. Al though welded texture is change in thickness of this flow sequence to the east toward not widesprea d within these ash-flow depos it s, one local ity Quartz Lake, and to the south toward the Pillar where these was discov ered at the base of the unit where dense welding lavas are ap par ently ab sent (Fig. 2). and, local ly, a brown devitrified vitrophyre are well dis- played. The welded zone, about a metre thick, over lies an addi ti onal 10 m of bedded crystal -vitric tuff and lapilli tuff GRAVES MEMBER (UNIT TG) in which weak welding is again evi dent in a metre-thick The Graves mem ber is named for dacite ash-flow tuffs zone just 3 m from the base of this sequence . The latter beds that are par tic u larly well ex posed in an iso to pi cally dated over lie a layer-par al lel, pla nar-crosslaminated lithic-vitric sec tion about 3 km southeas t of Mt. Graves. These tuff that is inter preted to repre sent a surge deposit . pyroclastic flows form resis tant blocky expo sures as much as 150 m thick, and ex hibit little variabil ity in thick ness Based on a U-Pb zir con date obtai ned from rocks near from one secti on to the next (Fig. 4, sec tions 5–8). The unit the middle of a secti on southeas t of Mount Graves (Fig. 4, is a disti ncti ve marker oc cupy ing a medial strati graphic po- sec tion 8), this ash-flow unit erupted at approx i m ately si tion be tween two in ter nally het er o ge neous mem bers, 192 Ma. This date firmly estab li shes the contemporaneity each com posed of gener all y sim ilar rock types. The con - of these ash-flow tuffs with compositionally simi lar de pos - tacts be tween the Graves mem ber and bounding rocks of its dated outside the map area (the south of Attycelley the Quartz Lake and Pillar mem bers are sharp and ap pear Creek) and include d in the Toodoggone form ati on as one of conform able throughout the refer ence area. The ash-flow the youngest known mem bers (i.e., Kemess memb er, tuff unit overli es a vari ety of dif ferent rock types at the top Diakow, 2001). of the Quartz Lake mem ber, includ ing flow-lam inate d rhy- PILLAR MEMBER (UNITS TPS, TPV) o lite (TQr), pyroxene-bear ing an de site lavas interlayered with crys tal tuffs and volca nic sandstone -siltstone layers The Pil lar mem ber con sti tutes the youn gest stra tig ra - contai ning pyroxene grains (TQv), and lo cally a hem atite phy presentl y recog nize d in the Toodoggone area. Ex cel- red monomictic boul der conglom erate with finer clastic lent expo sures are found at the local ity for which this se- interbeds or debris flow (TQs). In most secti ons, these mas- quence is named, as well as farther north in a downdropped sive ash flows contra st sharply with the overly ing well- fault block betwee n The Pillar and Mt. Graves (Fig. 2, 4). bed ded, mixed pyroclastic-epiclastic strata (TPs1). This The base of this unit rests on the Graves ash-flow tuff mem - unit is domi nated by vitric-crys tal tuffs, sand stones, ber and the top is not seen (eroded). The unit is siltstones and con glom er ates, and more lo calized lithologically het er o ge neous and has been sub di vided, accretionary lapilli tuff, lapilli tuff and tuff-brec cia that are where pos sible, into mappable volcaniclastic (TPs1, TPs2) disti nguishe d by abundant minute pyroxene grains. In a and flow (TPv1, TPv2) stra tig ra phy. Sec ond ary al ter ation few places, this bedded unit is absent and stratigraphically of lavas and clastic rocks to carbon ate , prehnite and a dis - higher pyroxene ande sit e lavas (TPv1) sit di rectly on the tinc tive pale pink ze o lite (laumontite?) is lo cally apparent ash-flow de pos its. throughout this succession. The ash-flow tuffs are rich in lithic frag ments, which At The Pil lar, unit TPs1 is rep re sented by at least 30 m may constitute up to 45% of the rock. The clasts are of well-strat ifie d, maroon to grey-green epiclastic rocks in- subangular to angu lar and typi cal ly less than 2 cm in di am e- clud ing vol ca nic peb ble to cob ble con glom er ate, in ter nally ter. Zones within the ash-flow tuffs may con tain con cen tra - lam inate d sandstone , siltstone and minor mudstone, local ly tions of block-size fragm ents, but these are uncom mon. exhib it ing crossbedding and cut-and-fill channel struc- The most abundant fragm ents are a mixture of fine-grained tures. Sim ilar stra tigra phy 2 km north-northeas t of The Pil - porphy rit ic and aphani ti c volca nic rocks in vary ing hues of lar across a major west erly-trending fault con tains a high red, brown and green. However , pale pink to flesh-col oured pro por tion of pyroclastic ma te rial in clud ing well-bed ded, dacitic fragm ents with minute hornblende and/or bio ti te coarse vitric-lithic tuff of airfall or igin , pla nar- grains are most di agnos ti c and useful for identi fying this crosslaminated lapilli tuff contai ning abundant angu lar unit. Ac ci den tal frag ments of pink ish bi o tite-hornblende volca nic fragm ents (<3 cm) of proba ble surge ori gin, and

100 Brit ish Co lum bia Geo log i cal Sur vey laharic brec cias with angu lar to subangular volca nic clasts case of the Maple Leaf pluton at Kemess South, em place- up to 0.5 m across. Farther north, this succes sion is thicker ment appears to be at a subvolcanic level. Monzonitic (>50 m) and com posed of thickly bedded, re worked vol ca- intru sions in the map area are relat ed to por phyry-style nic brec cias overlai n by grey-green, thin to medium -bed- min er al iza tion (e.g., at the Pil North, Sophia and Alexandra ded, moder ate ly well sorted volca nic sand stones, under - prospect s) and may have tem poral and geneti c links to epi- scor ing the rapid na ture of lateral fa cies changes. ther mal pre cious-metal min er al iza tion (e.g., at the Sickle- The lower epiclastic-pyroclastic suc ces sion is con- Griz showings, descri bed below). form ably overlai n by ba saltic to andesitic lavas (TPv1) that A large com posit e pluton is well exposed in the lower form the peak of The Pil lar and occupy lower ridges to the part of Jock Creek; to the north, this body proba bly under - north. Dark reddish to purpli sh grey flows are moder ate ly lies much of the low tree-covered re gion adja cent to the (10–15 vol. %) to strongly (25–30 vol. %) plagiocla se Toodoggone River and, to the south, it extends to the Finlay phyric with sub or di nate clinopyroxene pheno crysts (com - River. In order to rati onal ize field obser va ti ons, it was nec- monly <1 mm but local ly up to 3 mm, and typi cal ly com - essary to subdi vide the Jock Creek pluton into an older prising 1–2% but reaching 5 vol. % of the rock). The abun - (Bqm1) and younger (Bqm2) phase. The lower m ost ele - dance and size distri buti on of plagioclase and ment of the Toodoggone stra tig ra phy, a basal con glom er ate clinopyroxene pheno crysts vary sub stan tially from flow to below the Duncan ash-flow tuff mem ber, rests flow. Amygda loi dal texture s and thin flow brec cias are ob - nonconformably on the pluton in the extre me southeas tern served lo cally. part of the map area, whereas monzonite intrude s the lower - The upper m ost part of the Pillar mem ber is preserve d most Toodoggone rocks farther north at Jock Creek. The lo- in the downdropped fault-block north of The Pillar . The cati on of the contac t betwee n younger and older phases of base of the up per epiclastic-pyroclastic se quence (TPs2) the Jock Creek pluton is uncer tai n, and has been taken to be ap pears broadly con form able with the un der ly ing lavas. deli neat ed by a sharp contra st in the magneti c signa ture of The lower m ost beds com prise a buff to dark brown, clast- the rocks east of Jock Creek (Fig. 2). A sam ple of the youn - sup ported, vol ca nic cob ble to peb ble con glom er ate and ger monzonite phase is current ly being dated by the U-Pb moder ate ly well sorted pebbly sandstone . Higher in the tech nique. sec tion, these beds are in ter calated with pale grey-green to The younger (Bqm2) phase of the Jock Creek Pluton is pink weath er ing crys tal-lithic lapilli tuffs and reworked a pinkish grey, coarse-grained, equigranular to porphy rit ic, tuffs. At the northern m ost expo sures , the top of the suc ces - bio ti te-hornblende quartz monzonite with acces sory titan - sion (>130 m) is dom inate d by grey-green to buff, lam i- ite and opaque oxides . The porphy rit ic monzonite carrie s nated to me dium-bed ded vol ca nic sand stones and pebbly euhedral to subhedral plagioclase pheno crysts (up to 8 mm) sand stones with minor interbedded siltstone and mudstone. set in a finer grained groundmass of potas sium feldspar and The overly ing plagioclase- and pyroxene-phyric lavas quartz. Plagioclase crys tals usu ally dis play os cil la tory zon - (TPv2) are tex tur ally and min er al og i cally sim i lar to the ing and are flecked with sericite. In ter sti tial po tas sium feld - older flows (TPv1) of the Pillar mem ber, and would be dif - spar is gen er ally more strongly al tered to sericite and clay ficult to disti nguish in the absenc e of an inter vening miner als. Alth ough little quartz is gener ally app aren t in epiclastic-pyroclastic sequen ce (TPs2). How ever, some of hand spec i men, thin-sec tion ex am i na tion re veals some 10– these flows are dis tinctly vis cous with well-de vel oped flow 15 vol. % of the mineral . The pre dom inant ferrom agnesi an lamina ti ons and have a rhyodacitic com posi ti on. Flow mineral is euhedral to subhedral hornblende (<7 mm) that is brec cias are gen er ally better de vel oped than in the andesitic com monly alter ed to chlorite. Subhedral to anhedral bi oti te lavas and flow laminae lo cally bear pink devitrification (<4 mm), also vari ably al tered to chlorite, is pres ent in mi- spots. nor amounts, along with acces sory titan it e (<1 vol. %) and opaque oxides . Black Lake Intrusive Suite (Units Bqm, Bmp, Bd) The older phase (Bqm1) of the Jock Creek pluton is a Plutons and minor intru sions (dikes and sills) of the medium -grained, equigranular quartz monzonite, miner al - Early Ju ras sic Black Lake In tru sive Suite are found ogi cal ly sim ilar to the younger phase. However , the amount throughout the map area; the largest bodies occur at the of quartz is nota bly higher (~20 vol. %) and oc curs as eastern mar gin of the map area and along the Pil lar Fault. anhedral grains clearly visi ble in hand sam ple. Anhedral These in tru sions are tem po rally and prob a bly ge net i cally po tas sium feld spar oc curs as a late in ter sti tial phase. Bi o tite relat ed to extru sive rocks of the Toodoggone formation. is the domi nant mafic min eral, ac compa nied by lesser amounts of hornblende and trace titan it e and opaque ox- Typi cal Black Lake intru sions in the study area are bi o - ides. tite- and hornblende-bearing quartz monzonites with a me- dium to coarse-grained equigranular to porphy rit ic texture . Plutons exposed along the Pillar Fault are quartz These plutons dif fer slightly in com posi ti on from those as- monzonite and porphy rit ic monzonite; the latter phase is so ci ated with Au-Cu por phyry min er al iza tion at the asso ci ate d with Cu-Au porphyry prospect s in the vicin it y Kemess de pos its in that the latter in tru sions are less dif fer - of Pil North. The porphy rit ic phase of the pluton (Bmp) east en ti ated and com prise monzodiorites and medium to of the fault cuts the youngest part of the Toodoggone stra- coarse-grained monzonite por phy ries. These min er al ized tigra phy (Fig. 2). This indi cat es that the intru sion is youn- plutons also have a dis tinctly tabu lar geom etry , and in the ger than 192.3 ± 0.4 Ma, the U-Pb isoto pic age of the

Geo log i cal Field work 2004, Pa per 2005-1 101 Graves mem ber in the upper part of the Toodoggone stra- Dupont of Can ada Ex plo ra tion Lim ited com mis sioned tig ra phy. the 100 tonnes/day under ground Baker mine, the first mine to open in the region, in April, 1981 (Barr et al., 1986). It Small dioritic stocks and dikes of the Black Lake Intru - ceased op er a tion in No vem ber 1983, af ter pro duc ing sive Suite cut the Toodoggone for mation as well as 1196 kg of gold and 23 085 kg of sil ver from 77 596 tonnes monzonitic rocks of the Jock Creek pluton. The largest of ore mined and milled from the A vein (MINFILE). Mul - diorite intru sions are northerl y-trending, elongate bodies ti nati onal Resource s Inc. purchas ed the propert y from under ly ing val ley slopes and ridge crests just west of Jock Dupont in 1985 and Sa ble Resource s Lim ited ac quired the Creek. The rocks are pinkish grey to dark grey-green, fine Baker mill from Dupont in 1989. Mul ti nati onal out lined a to coarse-grained bi oti te-clinopyroxene diorites. Anhedral small tonnage on the B vein and, with Sable as a partner , to subhedral crystal s (<5 mm) of pyroxene and plagioclase mined and proces sed modest tonnages from the vein unti l are intergrown with bio ti te and minor (<2 vol. %) inter sti - 1996 when Sa ble acquire d the propert y out right from Mul - tial quartz and opaque ox ides. Coarsely crystal line va ri eties tina tional. Since that time, Sa ble has, on an in ter mittent ba - local ly contai n fresh bi oti te oikocrysts up to 1.5 cm across. sis, extra cted and proces sed lim ited amounts of ore from Sec ond ary al ter ation min er als in clude sparse seri cite, both the A and B veins. chlorite and epidote. Sable Resource s Lim ited brought the Shasta deposit , Mi nor intru sions in the form of dikes, sills and small 8 km southeas t of the Baker mine, into produc ti on in Oc to- plug-like bodies are proli fic throughout the map area. The ber 1989, conti nu ously extra cting ore from the Creek and most com mon dikes are pinkish grey to buff weather ing, JM zones unti l April 1991. During this time, 601 kg of gold medium -grained to por phyrit ic monzonite; pale pink to and 32 932 kg of silver were produced from 122 533 tonnes red dish weath er ing, apha ni tic to por phy ritic (rarely me- of ore pro cessed at the Baker mill. The two ore zones were dium-grained) leucomonzonite (to syenite?) car ry ing small first mined by small open cuts; under ground devel op m ent amounts (typ ically trace to 1 vol. %) of mafic miner als; and on each followed . Small tonnages of ore were mined from quartz± bi o tite por phyries. Ba saltic to andesitic dikes simi - the JM and Creek zones in 2000, 2003 and 2004. lar in com posi ti on to pyroxene-bearing extru sive rocks in the upper part of the Toodoggone for mation are also com- In 1986, Cheni Gold Mines Ltd. purchas ed the Law- mon. All dikes are gener all y steeply dipping and exhibi t a yers prop erty from Kennco Western Ltd. Cheni commis - re gional, north to north-north west erly pre ferred ori en ta- sioned the mine in 1989 with a com bined reserve for the tion. AGB, Cliff Creek and Duke’s Ridge zones of 1.757 mil lion tonnes grading 6.72 g/t Au and 243 g/t Ag. The AGB de- posit was mined unti l 1991 using under ground shrinkage MINERAL OCCURRENCES AND and blast-hole stoping methods, but the Cliff Creek and EXPLORATION Duke’s Ridge zones were not mined. The steeply dipping AGB deposit , with widths of up to 12 m, had been traced The Toodoggone area has a rich his tory of min eral ex - north along strike for about 550 m. Miner al iza tion con- plora ti on and is a suc cessful mining distri ct. The pre mier sisted of na tive gold, na tive sil ver, electrum, acanthite and explo ra ti on tar gets have been, and conti nue to be, large ton- lesser chal co py rite, sphalerite and ga lena in quartz veins, nage Cu-Au porphyry sys tems and small, high-grade, pre - stockworks and chalce dony-he aled brec cias. Ap prox i- cious-metal epi ther mal vein system s. A regional synop sis mately 620 000 tonnes of ore were milled, although this to - of previ ous explo ra ti on work is given below , along with de- tal include s an esti mated 60 000 tonnes from the Al prop- scripti ons of some of the newer discov er ies and prospects erty (MINFILE 094E 091) locat ed north of the in the study area. Toodoggone River. A total of 5042 kg of gold and 113 184 kg of sil ver were recov ered. Cheni re claimed the Recent History of Toodoggone Mineral propert y in the late 1990s and its tenure over the site was Exploration later relinquished. The propert y was staked by Guardsm en Resource s Inc. in 2000 and 2001, and optioned the fol low- ing year to Bishop Re sources Inc. In 2004, Bishop followed The Toodoggone min ing camp was sys tem at i cally up encour ag ing float anom ali es with a 1000 m trenching eval uate d for its poten ti al to host bulk tonnage mineral de- pro gram on the pla teau imme di ately west of the Cliff Creek posit s in the mid-1960s by Kennco Ex plo ra tions (West ern) zone. Lim ited. They con ducted a re gional geo chem i cal sam pling program that led to the discov ery of the first known por- Por phyry min er al iza tion was first iden ti fied in the area phyry-style base-metal and vein-type precious metal tar - of the Kemess South de posit in 1983. Exten sive drilling gets in the Toodoggone region. Among the de posit s found program s conducte d by El Condor Re sources Ltd. from were Chappelle (Baker), Lawyers (AGB zone) and Kemess 1990 to 1993 out lined a geolog i cal resource for the Kemess North. Fol low-up ex plo ra tion by Kennco and other com pa- South de posit of 250 mil lion tonnes grading 0.62 g/t Au and nies began in the late 1960s and conti nued inter mit tently 0.22 g/t Cu (Rebagliati et al., 1995a). Royal Oak Mines Ltd. through the 1970s into the early 1990s. This explo ra ti on re- purchas ed the propert y and ini ti ated site clearing and mine sulted in the devel op m ent of small Au-Ag mines (Baker, construc tion in July 1996. The mine was com missione d in Law yers and Shasta) cen tred on epither mal quartz-vein Octo ber 1998. In the spring of 1999, Royal Oak becam e in- systems and the Kemess South porphyry Au-Cu mine. solvent and the mine was purchas ed by Northgate Explo ra -

102 Brit ish Co lum bia Geo log i cal Sur vey tion Ltd. (now Northgate Miner als Corpo ra ti on). The mine up to several centi meter s wide. In order of decrea sing abun- presentl y oper ate s at rate of approx i m ately 50 000 tonnes dance, they comprise galena, sphalerite, tetrahedrite, per day and produces about 300 000 ounces of gold and 75 chal co py rite and pyrite. Chip samples across dis crete veins mil lion pounds of copper per year. Re cent explo ra ti on in have yielded grades as high as 9.5 g/t Au and 407 g/t Ag the area of the mine has focuse d on the Kemess North de - over 3 m. Assay result s from the first two holes drilled into posit, where dia m ond drilling to deeper levels has ex- the lower vein sys tem have re turned encour ag ing re sults panded the size of the deposit . A feasi bil ity study on (e.g. 3.18 g/t Au and 107.8 g/t Ag over 2.5 m from the Kemess North, com pleted in Octo ber 2004, identi fied a re- footwall porti ons of the 570A vein; see Stealth Min er als source of 414 mil lion tonnes grading 0.31 g/t Au and 0.16 Ltd. news re lease, July 16, 2004). g/t Cu. The proposed open pit mining project has now entered the harmonized Federal/Provincial environmental Au-Cu Porphyries review process. Al though the Kemess South mine is outside the current PIL NORTH (MINFILE 094E 083) AND map area, it has contri buted signif i cant ly to the reju vena - VICINITY tion of ex plo ra tion through out the Toodoggone mining The Pil North propert y is locat ed at the west ern mar gin camp. Its im portanc e as a rem ote major open-pit mining op- of the map area (Fig. 6). It is under lai n by a quartz er a tion ser viced by hy dro elec tric ity, a mod ern mill ing fa- monzonite to por phyrit ic monzonite stock that straddles the cil ity and a substa nti al in-ground mineral resource cannot Pil lar Fault and in trudes andesitic lavas of the Metsantan be under sta ted. This infra struc ture is crucia l for future mine mem ber in the west and some of the youngest strati graphic de vel op ment in the Toodoggone re gion, as it may be come a units of the Toodoggone form ati on in the east (Fig. 6). Ex - centra l milling com plex capable of supporting numerous plora ti on by Finlay Miner als Ltd. has identi fied a num ber satellite orebodies. of Cu-Au geo chem i cal anom a lies that are co in ci dent with in duced po lar iza tion chargeability anom a lies. Some of Epithermal Au-Ag Veins: Sickle-Griz (MINFILE these anom ali es coin cide with pronounced propylitic and 094E 237) phyllic al ter ation zones and are thus prime tar gets for por- phyry-style min er al iza tion (i.e. the Northwest and North - Stealth Min er als Ltd. dis cov ered the Sickle-Griz Au– east zones, Fig. 6). Other geo chemi cal anoma lies have a Ag–base-metal epi ther mal vein prospect in 2003. Two polymetallic signa ture that may be indic a ti ve of buried vein phys i cally dis tinct, top o graph i cally sep a rated vein sys tems sys tems (i.e. East, Milky Creek, NW Exten sion and WG are rec og nized cut ting Toodoggone volca nic rocks. Five Gold zones). discret e paral lel veins (named 570A to 570E) are found in the bot tom of the cirque occu pied by Quartz Lake (Fig. 5). The Northwest zone is charac ter ized by a 200 by 600 m They have an azi m uth of 155° and dip 65° to the west. Sev- geo phys i cal anom aly that co in cides with el e vated Cu-Au eral of the most prom inent veins on surface (570A and soil val ues and lo cally in tense sili ci fi ca tion, bleach ing and 570B) are up to 13 m in width and over 100 m in length, and py rite-seri cite al ter ation of the monzonitic host rock. Chal - transect a monot o nous sequence of grey-green por phyrit ic co py rite ac com pa nies py rite in nar row quartz string ers and andesites assigne d to the Metsantan mem ber (Fig. 5, 6). in ar eas where more perva sive sil ica-flooding is devel oped. Flow-lami nated rhyolitic dikes and sills, a compar a tively Late-stage, pur ple anhydrite string ers cut the min er aliza - rare occur rence in the Toodoggone camp, are also a tion. The North east zone lies east of the Pil lar fault and is conspicuous feature of this area (Fig. 5). under lai n by quartz-bearing flows of the Metsantan mem- ber that are weakly to moder ate ly oxi dize d (Fig. 6). The The 570 veins vary in appear ance from massive , dif - hostrock dis plays lo cally in tense quartz-seri cite-py rite al - fusely lay ered white quartz to multi ple lay ers of comb-tex - ter ation, with dissem inate d pyrit e reaching up to 15 vol. %; tured quartz al ter nat ing with cal cite spar (Fig. 7). Po tas - in places, goethite and jarosite are well de vel oped. sium feldspar al ter ation ad ja cent to the veins is wide spread, vary ing in in ten sity from in cip i ent to mod er ate, and im parts The East and Milky Creek zones have a polymetallic a pale pink to brownish hue on host andesites. geo chem i cal sig na ture char ac ter ized by highly anom a lous Au and Ag val ues accom panied by incon sis tent Cu and Zn The second vein system , sit uate d about 150 m higher abundance s. The East zone include s quartz stockworks and on the ridge above the 570 veins, exhib it s more of a brecciated monzodiorite healed with silica; both are min er - stockwork char ac ter, with mul ti ple gen er a tions of quartz alized with small amounts of bar ite, ga lena and sphalerite. veins and quartz-brec cia veins occu py ing a zone more than The Milky Creek zone is char acter ized by a potassic feld - 75 m wide and hosted by dacitic ash-flow tuffs near the base spar-magne ti te-quartz stockwork within strongly clay-al- of the Graves mem ber (Fig. 5). Adular ia sam pled from nar- tered monzonite. Chip sam pling across a 10 m wide seg- row al ter ation selvages adja cent to quartz veins at both the ment of the Milky Creek showing aver aged 0.52 g/t Au. lower and upper vein sys tems is being used to obtai n Ar-Ar The NW Exten sion, a quartz-barit e stockwork anom alous iso to pic ages for the min er aliza tion. Since the Graves mem - in Cu and Pb, may repre sent a polymetallic vein on the pe- ber has been dated at 192.3 ± 0.4 Ma, this estab li shes a max- riphery of a porphyry sys tem. The WG Gold zone com - im um age for em placem ent of the upper vein stockwork. prises quartz veins, stockworks and brec cias confine d to a Sulphide miner als in the veins occur as fine dissem ina - steeply dipping, northwest -trending cor ridor that extends tions, patchy ag gre gates and semimassive to massive layers for over a kilo metre. The veins are devel oped within quartz

Geo log i cal Field work 2004, Pa per 2005-1 103 monzonite and local ly carry vari able quanti ties of barit e tite(±specularite)-chal co py rite stockwork veins en vel oped and galena . Sam ples of quartz float carry up to 16.8 g/t Au. by potas sium feldspar alter ation (Fig. 8). Narrow , drusy quartz stringers cut the other vein types. Intens e pyrit e-seri- SOFIA (MINFILE 094E 238) cite al ter ation oc curs lo cally within the outcro p. Grab sam- Por phyry-style min er al iza tion at So fia was dis cov ered ples from the prospect have produced assay s of up to in the sum mer of 2004. The showing is restri cted to a single 0.22 g/t Au and 0.05 wt. % Cu (see Stealth Minerals Ltd. outcrop (25 by 25 m) which is locat ed on the west bank of news re lease, July 16, 2004). the Toodoggone River, approx i m ately 2.7 km northwest of ALEXANDRA PROSPECT the mouth of Jock Creek (Fig. 6). . The main hostrock is a medium to coarse-grained equigranular monzonite The Alexandra Au-Cu porphyry prospect was also dis- (Bqm2), al though min er al iza tion also oc curs within ad ja- covered in 2004. It is locat ed on a ridge 3.3 km west-south- cent augite-phyric lavas that exhibi t pronounced alter ation west of the conflu ence of Jock Creek and the Toodoggone to chlorite and py rite (up to 8 vol. %). These lavas have ten - River, close to the in for mally named Sickle Creek (Fig. 6). tati vely been assigne d to the volca nic unit of the Quartz The showing consis ts of quartz-magne ti te stringers cutti ng Lake mem ber. Min er al iza tion con sists of subparallel mag - in tensely bleached, clay-altered andesitic vol canic rocks of neti te veinlets and subse quent layered quartz-magne - the Metsantan mem ber. The al ter ation zone is co in cident

R ' e iiv 0 n e e 4

r º o r g Quartz Lake 6 g 2 d o 1 T o o Griz Lake

P M t. i G r a v e s l l Sickle Creek a +

r

B

l

a 1 < c Sofia X < k X 5 < 2 < 4 X F < 3 Alexandra 57º20' a Sickle-Griz u + X l Pil North X t + kkk X X eeekkk + eeeeee X F rrreee a CC + u X l + t + + + kkkk + kkkk cccc +

oooo JJJJ + + rr + ee vv T h e + + ii P i l l a r + R + 57º15' < e. Pil Prospects k a 1 - Northwest zone yy L a k ll c 2 - Milky Creek zone n l a ii B 3 - East zone F 4 - WG Gold zone 0 2 4

º 5 - Northeast zone 7

2 kilometres 1 Fig ure 6. Lo ca tion of se lected Au-Cu porphy ry and Au–Ag–base-metal epi ther mal prospects dis cussed in the text in re la tion to their geo - logical set ting as de ter mined in this study. Leg end for geo logical units is the same as Figure 3.

104 Brit ish Co lum bia Geo log i cal Sur vey Fig ure 7. View of the 570A vein, dis play ing al ter nat ing bands of quartz and cal cite spar, Quartz Lake, Sickle-Griz prospect. with ele vate d Au, Cu and Ag val ues in soils that cover an raphy . These new mem bers contra st with older 800 by 250 m area. The showing approache s within about Toodoggone strata by the no table pres ence of 300 m of the Jock Creek monzonite (Bqm2) contac t with clinopyroxene, and the scarcit y of quartz, bio ti te and Metsantan lavas, and extends downslope to the north and hornblende in the volca nic rocks. Their age is roughly east of the ridge. that of the Graves mem ber (~192 Ma), as es tab lished by U-Pb iso tope sys tem at ics.

SUMMARY AND CONCLUSIONS · The princi pal intru sions in the map area are equigranular to porphy rit ic quartz monzonite and The main result s of the 2004 field program can be sum - monzonite and minor diorite of the Early Juras sic marized as follows: Black Lake Intru sive Suite. A com posit e stock in the · The gen eral stra tig ra phy of the Toodoggone region, southeas tern part of the study area, named the Jock namely rocks from the Late Carbon if er ous to Early Creek pluton, is formed by early and late monzonitic Perm ian Asitka Group, Late Tri as sic Takla Group and phases. Basal con glom er ates of the Toodoggone for - Early Ju ras sic Hazelton Group, extends into the study mati on rest nonconformably on the older phase (latest area. The vol ca nic stra tig ra phy of the Toodoggone for - Trias sic ?), whereas the younger monzonite intrude s mati on has been expanded in the upper part, rocks as high in the Toodoggone form ati on as the stratigraphically above the Metsantan and Saunders Metsantan mem ber (~198 Ma or slightly younger?). mem bers, to include three new in for mal memb ers, the Quartz Lake, Graves and Pil lar, from oldest to youn - · These in tru sions have a sig nif i cant ge netic as so ci a tion gest, re spec tively. They con stitute a di verse as sem- with Cu-Au porphyry miner al iza tion south of the blage of lavas, ash-flow tuffs, and as so ci ated study area at the Kemess depos it s. The new mapping volcaniclastic rocks cover ing a wide compositional ex tends the known dis tri bu tion of po ten tially min er al- spec trum from ba salt to rhy o lite. Epiclastic vol ca nic ized monzonitic intru sions north of the Finlay River, to sand stones and con glom er ates in ter leaved with ash- include the Jock Creek pluton and their unnam ed coun- flow and air-fall pyroclastic units form distinctly bed - ter parts ad ja cent to the Pillar Fault at the Pil North ded sec tions within an oth er wise mas sive flow stra tig - propert y. The Jock Creek body appar entl y hosts two

Geo log i cal Field work 2004, Pa per 2005-1 105 new Au-Cu porphyry prospect s in the map area, the Toodoggone River map aea, north-central Brit ish Colum - Sophia and Alexandra. bia (parts of NTS 94E/2,6 and 7); BC Minis try of Ener gy and Mines, Open File Map 2004-4, 1:50 000 scale. · Min er al ized epi ther mal quartz-cal cite veins and Diakow, L.J. (2001): Ge ol ogy of the South ern Toodoggone River stockworks, such as those discov ered on the Sickle- and North ern McConnell Creek map areas, north-cen tral Griz prop erty, con sti tute a sig nif i cant ex plo ra tion tar - Brit ish Colum bia (parts of NTS 94E/2, 94D/15 and 16a); get. These min er alized sys tems af fect rocks as young BC Min istry of En ergy and Mines, Geoscience Map 2001- as the Graves mem ber (~192 Ma). Isoto pic dating, us - 1, 1:50 000 scale. ing U-Pb and Ar-Ar system atics , is current ly in prog- Diakow, L.J., Panteleyev, A. and Schroeter, T.G. (1993): Ge ol ogy ress in order to constra in poten ti al ge netic rela ti on- of the Early Juras sic Toodoggone Forma tion and gold- ships betwee n porphyry and epi ther mal base- and silver deposits in the Toodoggone River map area, northern Brit ish Co lum bia; BC Minis try of Ener gy, Mines pre cious-metal de pos its. and Pe tro leum Re sources, Bul le tin 86, 72 pages with maps at 1:100 000 scale. ACKNOWLEDGMENTS Diakow, L.J., Panteleyev, A. and Schroeter, T.G. (1985): Ge ol ogy of the Toodoggone River area, NTS 94E; BC Min is try of We grate fully ac knowl edge the gen er ous fi nan cial and En ergy, Mines and Pe troleum Re sources, Pre lim i nary logis ti cal support this project has re ceived from Stealth Map 61, 1:50 000 scale. Min er als Ltd., Northgate Min er als Corp., Finlay Min er als Eisbacher, G.H. (1974): Sed i mentary history and tectonic Ltd., Sable Resource s Ltd. and Bishop Gold Inc. We have evolution of the Sustut and Sifton basins, north-central bene fited from geo log i cal dis cus sions with the geo log i cal Brit ish Co lum bia; Geo log i cal Sur vey of Can ada, Paper staff, stu dents and pros pec tors rep re sent ing these com pa- 73-31, 57 pages. nies in the field. Their geolog i cal contri buti ons have led to Legun, A. (2001): Ge ol ogy of the South ern McConnell Range im provem ents in our work. We also thank Stealth Miner als and Sustut River areas, Brit ish Colum bia (parts of NTS 94D/3, 7, 9, 10, 15, 16); BC Min istry of En ergy and Mines, Ltd. for provid ing copies of their de tailed outcrop maps to Open File Map 2001-18, 1:50 000 scale. supplement our own mapping. Monger , J.W.H. (1977): The Tri as sic Takla Group in McConnell Creek map-area, north-cen tral Brit ish Co lum bia; Geo log i - REFERENCES cal Sur vey of Can ada, Pa per 76-29, 45 pages. Barr, D.A., Drown, T.J., Law, T.W., McCreary, G.A., Muir, W.W., Rebagliati, C.M., Bowen, B.K., Cope land, D.J. and Niosi, Paxton, J.M. and Ros coe, R.L. (1986): The Baker Mine D.W.A. (1995a): Kemess South and Kemess North por - Op er a tion; Ca na dian In sti tute of Min ing and Met al lurgy, phyry gold-cop per de pos its, north ern Brit ish Co lum bia; in Bul le tin, Vol ume 79, No. 893, pages 61-68. Por phyry De pos its of the North west ern Cor dil lera of North America, T.G. Schroeter, ed i tor, Ca na dian In sti tute Diakow, L.J. (2004): Ge ol ogy of the Samuel Black Range Be - of Min ing and Met al lurgy; Spe cial Vol ume 46, pages 377– tween the Finlay River and the Toodoggone River, 398.

Fig ure 8. Stockwork Cu-Au miner al iza tion at the Sofia show ing.

106 Brit ish Co lum bia Geo log i cal Sur vey Schiarizza, P. (2004a): Ge ol ogy and mineral oc cur rences of Shives, R.B.K., Carson , J.M., Dumont, R., Ford, K.L., Holman, Quesnel Terrane, Kliyul Creek to Johanson Lake P.B. and Diakow, L. (2004): He li cop ter-borne gamma-ray (94D/8,9); in Geo log i cal Field work 2003, BC Min is try of spectrometric and magnetic total field geophysical survey En ergy and Mines, Pa per 2004-1, pages 83–100. (parts of NTS 94D/15, E/2, 3, 6, 7, 10, 11); Geo log i cal Sur- vey of Can ada, Open File 4614. Schiarizza, P. (2004b): Ge ol ogy of Kliyul Creek–Johanson Lake area, parts of NTS 94D/8 and 9; BC Min istry of En ergy and Mines, Open File Map 2004-5, 1:50 000 scale.

Geo log i cal Field work 2004, Pa per 2005-1 107 108 Brit ish Co lum bia Geo log i cal Sur vey