GEOLOGY OF THE RIVER-DUNCAN AREA, VANCOWER ISLAND" (92C/16; 92B113) By N. W. D. Massey and S. J. Friday

KEYWORDS: Regional geolo&y. VancouverIsland, Sicker INTRODUCTION Group,McLaughlin Ridge Formation, Karmutsen Forma- tion,Nanaimo Group, Cowichan uplift, thrusts, massive In 1986, a program of 150 000-scale regional mapping sulphides, rhodonite. gold. was initiated by the Geological Survey Branch in southern

1

Sicker Group

Buttle Lake Uplift Cowichan Uplift 50' 50' Narloose Uplift - cp

49' ' 49

126' 125' 124'

Figure 1-6-I. Location of the Sicker Project area, southern , in relation to the three majcmr geanticlinal uplifts cored by Sicker Group rocks (after Brandon er ai., 1986). Planned field seasons are indic:ated.

~ * This project is a contribution 10 the CanadatBritish Columbia Mineral Development Agreement. Ministry of Energy. Mines and Petroleum Resources. Geological Fieldwork, 1987, hper 1988-I 81 Figure 1-6-2. Geology and structure of the Duncan and areas (see also facing page).

Vancouver Island, emphasizing thePaleozoic Sicker Group. em margin of the area. Many otherpaved roads are present in A4-year program was planned, coveringthree 150 OOO theeast and south within the municipalities of North NTS sheets centred on the main Sicker Group outcrop area Cowichan and Ladysmith. Access to the western half of the within the Cowichan uplift (Figure 1-6-1). Initial mapping in area is provided by an extensive network of logging roads in the Cowichan Lake area (92Ci16) was reponed on last year various states of upkeep. Shoreline exposures are easily (Massey and Friday, 1987) and releasedas OpenFile 1987-2 accessible by boat. (Massey era[., 1987). During the 1987 field season, fieldwork was extended into the northeastem quadrant of the Cowichan Lake sheet and PREVIOUS WORK eastwards into the Duncan map sheet (92BiI3), excluding the The Sicker Group was first defined as the . Road access in the area is excellent with the Series by Clapp(Clapp, 1912: Clapp and Cooke, 1917) main Island Highway running northwards through the east- within the Duncan area,although erroneously interpreted as 82 youngerthan the Karmutsen Formation (Vancouver Series). Cowichanuplift has been suggested by SotherlandBrown, Later workers in theButtle Lake and CowichanLake areas based on 150 000-scale malppingin the/ilberni-Bamfield recognized that the Sicker Group is indeed older (Gunning, corridor undenken by the (;eological Survey of Canada in 1931; FY1es, 1955). and colleagues "lapped large support of theLITHOPROBBE 1 Project (Sutherland Brown portions Of Vancouver Islandincluding the Duncan and and Yorath, in preparation; !jutherland Brown ef al,, 198,j). Cowichan areas (Muller, 1982, 1985).Detailed investiga- A similar revision has also ken made, independently, by tions of small areas around Duncan have also been reported on by Eastwood (1979,1980, 1982). hasin Buttlethe Lake uplift (Juras, 1987).Biostratigraphic and radiometric dating of the rocks of southern Vancouver Stratigraphic studies of the Sicker Group were conducted Island has been summanzed by Muller andl Jeletzky (1971)). byYole (1964,1965, 1969) andMuller (1980). A major Brandon el ol. (1986)and Armstrong et al. (unpublished revision of thestratigraphy of theSicker Group of the preprint). 83 REGIONAL SETTING MCLAUGHLIN RIDGEFORMATION The Chemainus River-Duncan area straddles the eastern The Nitinat Formation is overlain, apparently con- end of the Cowichan uplift, one of a series of major gean- formably, by a heterogeneous sequence of intermediate to ticlines typical of the structural fabricof southem Vancouver felsic volcanics and volcaniclastic sediments. In the Alberni Island (Figure 1-6-1). The area lies within the Wrangellia and Cowichan Lake areas, the McLaughlin Ridge Formation terranewhich on Vancouver Island comprises three thick is characterized by the development of thickly bedded, mas- volcano-sedimentary cycles (Paleozoic Sicker Group, Upper sive tuffites and lithic tuffites with interhedded laminated Triassic Vancouver Group and Jurassic Bonanza Group) sandstone, siltstoneand argillite. Associated breccias and overlapped by Upper Cretaceous sediments of the Nanaimo lapilli tuffs are usually heterolithic and include aphyric and Group. porphyritic (feldspar? pyroxene? hornblende) lithologies, commonly maficto intermediate in composition. Felsic tuffs are rare. STRATIGRAPHY However, within the Duncan area, the McLaughlin Ridge The oldest rocks in thearea belong to the Paleozoic Sicker Formationis dominated by volcanics with onlyminor Group (Figure 1-6-2) which contains volcanic and sedimen- tuffaceous sediment. Thevolcanics are predominantly inter- tary units ranging in age from Middle Devonian (?) to Early mediate to felsic pyroclastics, commonly feldspar crystal- Permian. These are intruded by mafic sills coeval with over- lapilli tuffs and heterolithic lapilli tuffs andbreccias. A thick lying basaltic volcanics of the Late Triassic Karmutsen For- package of quartz-crystal, quartz-feldspar-crystal and fine mation. All of these sequences have been subsequently in- dust tuffs is developed in the Chipman Creek-Mount Sicker truded by granodioritic stocks of the Middle Jurassic Island area and is host to polymetallic sulphide mineralization. This Intrusions. Late Cretaceous sedimentsof the Nanaimo Group package thins to the west where it interfingers with andesitic lie unconformably on the older sequences. lapilli tuffs and breccias. It appears to be stratigraphically high within the formation. A distinctive maroon schistose heterolithic breccia and lapilli tuff forms the uppermost unit SICKER GROUP within the McLaughlin Ridge Formation and is seen in the Since the initial work of Clapp (1912) there have been Chipman Creek-Rheinhart Creek area. Most contacts with several attempts to formally subdivide the Sicker Group. overlying formations are faulted. Muller (1980) proposed four subdivisions which,in ascend- The McLaughlinRidge Formation is equivalent to the ing stratigraphic order, are the Nitinat Formation, the Myra lower parts of the Myra Formation of Muller (1980). Formation, an informalsediment-sill unit and the Buttle Lake Formation. Recent paleontological and radio- CAMERONRIVER FORMATION chronological studies (Brandon et a/., 1986). coupled with newer mapping (Sutherland Brown et al., 1986 Sutherland Theupper part of theSicker Group is made up of a Brown and Yorath, 1985), have thrown some doubt on these dominantly epiclastic sedimentary package. This is found subdivisions and their applicability in the Cowichan uplift. most often in fault contact with the lower volcanic units, but Newstratigraphic subdivisions have been proposed by is conformable on the McLaughlin Ridge Formation southof SutherlandBrown (in preparation) based on work in the Sansum Point and in the Chipman Creek-Rheinhart Creek Albemi area. Theseformational subdivisions have proven to area. The Cameron RiverFormation sediments lieunconfor- be applicable in the Cowichan Lake and Duncan areas also mably on theNitinat Formation on Hill 60 Ridge, near Paldi and have been adopted for this project. andFairservice Mountain. A similar unconformable rela- tionship is suspected west of Banon Creek. In the south of the area (Hill 60 and the Paldi inlier) the NITINATFORMATION base of the sedimentarv unitis marked bv a 100 to200-metre- The lowermostunit in the SickerGroup is avolcanic thick sequence of ribdon cherts,IaminGed cherts and cherty package characterized by pyroxene-feldspar porphyritic tuffs that continues westward into the Cowichan Lake area. basaltic andesites, typically occurring agglomerates,as brec- This sequence passes upwards into monotonous thinly bed- cias, lapilli tuffs andcrystal tuffs.However, extensive pyrox- ded, turbiditicsandstone-siltstone-argillite intercalations. ene-phyric, amygdaloidal flows are developed in the Banon The basal ribbon cherts are absent north of the Chemainus Creek area. Pyroxenes are large, up to 1 centimetre diameter, River, where the thinly bedded turbiditic clastic sediments are euhedral to subhedral, and comprise 5 to 20 per cent of dominate. However, cherty tuffs and argillites are found at the rock.Plagioclase is equally abundant, but phenocryststhe base of the formation at Sansum Point. Thicker beds of are usuallysmaller, ranging up to 5 millimetresin diameter. sandstone,granule sandstone andconglomerate containing Amygdules present inflows andsome clasts in coarserclasts of cherty material,volcanic lithic clasts andfeldspar pyroclastics are infilled with chlorite,quartz, epidote or andpyroxene crystalsare also found withinthe formation. calcite.Minor laminated tuff andtuffaceous sandstoneare Thin crinoidal calcarenitesand limestones are interbedded present locally. Massive and pillowed aphyric and diabasic with sandstone and argillite near the top of the formation at mafic flows are also developed, particularly on the north Mount Brenton, at Separation Point and in theHaslam Creek slope of CoronationMountain andFairservice Mountain.area. This volcanic unit isequivalent to the Nitinat Formation of In contrast to the AlberniXowichan Lake area, limited Muller (1980). volcanismto appears haveearly duringcontinued Cameron 84 RiverFormation sedimentation in theMount Whymper- The numerous intrusion:. are believed to have occurred Rheinhart Creekarea. This produceda bimodal suite of during dilation of the Sicker Group basement in the Late aphyric basaltsand rhyolites, generallyforming sills and Triassic, and acted in part as feeders to the overlying vol-. dykes though some amygdaloidal basalt flows occur. Similar canics (Figure 1-6-3). Elsewhere in Wrangellia the Kar- aphyricbasaltic dykes also intrude the underlying mutsen Formation volcanic!; overlap onto the basement ad McLaughlin Ridge volcanics. evidence of the rifting is ccvered. The Cameron River Formation is equivalent to the upper parts of Muller’s Myra Formation together with the sedi- NANAIMO GROUP ments of the informal sediment-sill unit (Muller, 1980). Clastic sediments of the Nanaimo Groilp unconformady overlie older volcanic units and the Island Intrusions. They MOUNTMARK FORMATION are mostthickly developed in the Map:leBay toMom: Prevost area, the Cowichan and Chemainu:, River valleys and Massive and laminated crinoidal calcarenites with chert the shoreline from Crofton Ladysmith. The sediment: 0:’ andargillite interheds occur in the Fairservice Mountain to area, south of the Cowichan River. Theydirectly overlie the Nanaimo Group constimte major fining-upward cycles Nitinat Formation volcanics in the west but are underlain by (Muller andJeletzky, 19701, of which the first two, thr: Cameron River Formation sediments to the east. The lime- Comox-Haslam andExtension-Protection-Cedar Distrct, stones are the uppermost unit in the Sicker Groupof the map are developed in the Duncan map sheet. area, though they are absent north of the Cowichan River where theCameron River Formation is overlain unconforma- COMOXFORMATION bly by Karmutsen Formation basalts or Nanaimo Group The basal Benson member of the Comox Formation is a sediments coarse, poorlybedded cobble andboulder conglomerate The Mount Mark Formation is the equivalent of the Buttle varying from about 100 metres thick in the Mount Tzuhalem Lake Formation of Muller (1980) andother authors (for and Stone Hill area in the east to absent in other locations. example, Yole, 1969).

VANCOUVER GROUP

KARMUTSEN FORMATION Basaltic volcanics of the Karmutsen Formation underlie Mount Whymper and the Mount Landalt-El Capitan area. Theycomprise pillowed flows, pillow breccias and hyaloclastite breccias interhedded with massive flows and sills. Typically thebasalts are feldspar-phyric, often with ragged or glomeroporphyriticfeldspars in afine-grained groundmass. Amygdules are common and are infilled with chlorite, calcite or epidote. The intrusive component increases toward the base of the sequence, which passes downward into diabase and gabbro bodies with intervening screens of Cameron River Formation sediments (Figure 1-6-3). These mafic sills and dykes are widespread in the area, occurringat deeper structural levels, though they are most commonly found intruding the Cam- eron River Formation (in the informal “sediment-sill unit”of Muller, 1980). They are medium to coarse-grained diabase, gahhro and leucogabhro with minor diorite, commonly por- phyriticwith feldspar phenocrysts often being glomeroporphyritic clusters up to 1 centimetres in diameter. Mafic phenocrysts are generally absent. Equigranular gab- bros are also common and coarse varieties contain frequent pegmatitic veinsand pods. Thick gabbro bodies under Mount Hall and Coronation Mountain show layering of porphyritic and nonporphyntic lithologies The intrusive bodies vary in size and form. Sill-like bodies aresubconcordant with beddingwithin thesediments, though they usually follow the foliation wherethis is strongly developed. They thus show a variety of attitudes from shal- Figure 1-63, Diaerammaticcross~sectioo.nottoscale.shou- low dipping to vertical. They may be as little as a few metres ing the relationship of Karmut,sen Formation volcanic and intrusive or up to 200 metres thick. Discordant dykes are also com- rocks to the riftedSicker Group basemcnt in the Mcunt mon, varying from IO centimetres to about 50 metres wide. Whympe-Kheinhart Creek area.

85 The conglomerates have rounded clasts which consist of a argillitewithout the intervening sandstones; the upper variety of volcanic and intrusive lithologies of immediate argillites may belong to the Cedar District Formation. local origin; larger boulders are often angular. Overlying sandstones are medium to coarse grained, grey with rusty weathered surfaces. They contain feldspar crystals INTRUSIONS and abundant lithic fragments, mostly volcanic of local provenance.Black plant-fragments are characteristic of SALTSPRING INTRUSIONS many beds. Calcareous cement is common and locally con- Coeval with the felsic volcanics in the McLaughlin Ridge cretions up to I metre diameter are developed. A few granule Formation is a suite of granodiorite stocks and quartz porph- and pebble conglomerate beds are interbedded with thesand- yry dykes collectively known as the Saltspring intrusions. stones.Several sandstone beds yielded abundantfossil faunas,including gastropods, pelecypods and possible The northem quarter of Maple Mountain is underlain by the westerly extension of the Mount Maxwell stock, centred broken ammonites and nautiloids. The thickness of the on Saltspring Island. This body consists of light grey to Comox Formation is estimated to vary from 0 to 350 metres. green, weak to moderately foliated, medium-grained grano- diorite with local fine-grained dacitic phases and a marginal HASLAMFORMATION feldspar porphyry. It intrudes Nitinat Formation volcanics The Haslam Formation consists of characteristic rusty and is itself cut by a large Late Triassic gabbro. weathering, black argillite and siltstone. It is fine to silty, Quartz and quartz feldspar porphyry dykes, previously often poorly bedded and friable, fracturing to pencil-shaped termed the Tyee Porphyry (Clapp and Cooke, 1917), are pieces. Interbeds of fine to medium-grained, grey silty sand- contemporaneous with the granodiorite, though never seen in stone are found within the argillites in the upper parts of the contact with it. They were probably feeders for felsic crystal formation (Cowichan member, Ward, 1978). They vary in tuffs in the McLaughlin Ridge Formation in the Chipman thickness up to 1 metre for massive to flaggy beds, though Creek-Mount Sicker area. The porphyries are usually well the more common graded sandstone-argillite turbidites aver- foliated and difficult to distinguish from the crystal tuffs age about 10 centimetres thick. Fossils are present within the when contact relationships with host volcanics are not clear. Haslam Formation, though poorly preserved due to the ubiq- Quartz phenocrysts are up to 1 centimetre in diameter, uitous pencil-and-rod fracturing, and include gastropods, rounded to ovoid in shape, and may be stretched in the pelecypods, ammonites and plant material. The thickness of foliation. They comprise up to 20 per cent of the rock. the Haslam Formation may reach up to 600 metres in the Plagioclase phenocrysts are smaller and vary in shape from (Ward, 1978). euhedral laths to rounded. They are sporadically altered to epidote. EXTENSION-PROTECTION AND CEDARDISTRICT FORMATIONS ISLANDINTRUSIONS Conglomerates of the Extension-Protection Formation Several granodioritic stocks of Middle Jurassic age occur conformably overlie Haslam Formation argillites on top of in the area. With the exception of the large Ladysmith stock, , representing the start of the second depsi- these granodiorite bodies are elongate in shape. The domi- tional cycle withinthe Nanaimo Group. Similar con- nant lithology is a medium to coarse-grained, equigranular glomerates are also found south of the Chemainus River and granodiorite to quartz diorite with a characteristic salt-and- between Ladysmith and Chemainus. These pebble to cobble pepper texture. Quartz is usually irregular in shape, often conglomerates are very similar to the Comox Formation interstitial to the feldspars. However, in the Ladysmith stock conglomerates being polymictic, subrounded to rounded large (up to 8 millimetres) rounded quartz grains are ubiq- clasts in a coarse sandstone matrix. Perhaps the only signifi- uitous. Feldspars are white, though some pink staining is cant difference is the presence of clasts of white quartz in the seen on weathered surfaces, and usually form subhedral Extension-ProtectionFormation, which are rare in the laths. Hornblende is the principal mafic mineral. It is tabular Comox Formation. Grey, medium to coarse-grained sand- to acicular, black to greenish black in colour and may be stnnes are interbedded with and overlie the conglomerates. slightly larger in size than the feldspars. Biotite is common in Argillites of the Cedar District Formation, which overlie theHill 60 andLadysmith stocks. Chlorite replaces the Extension-Protection Formation, are not exposed within hornblende and biotite in altered rocks. Colour index varies the map area. However,an unusual section of Nanaimo from 10 to 20 in the granodiorites, but may range up to 40 in Group sediments is exposed in the incised gorge along the diorites. White, fine-grained aplite dykelets and veins cut the Chemainus River just below its confluence with Chipman granodiorites. Creek. Argillites assigned to the Haslam Formation coarsen Most of the stocks are rich in inclusions, particularly in upwards through turbiditic sandstones into pebble con- marginal zones where agmatitic intrusive breccias are de- glomerate which is in turn succeeded by a fining-upward veloped. The angular to subrounded xenoliths are of local sequence of sandstones and argillites lithologically indistinct country rock lithologies showing a range of amphibolitiza- from the lower beds. The stratigraphic position of this se- tion and assimilation features. The xenoliths are normally quence remains uncertain. The coarse-grained beds may be randomly oriented, but within the Ladysmith stock some the Extension-Protection Formation, though it usually has zones of inclusionshave a parallelto subparallel basal conglomerate sitting directly on Haslam Formation arrangement. 86 MINORINTRUSIONS PHASE 3: LATE TRIASSIC A variety of dykes and small irregular intrusions occur Extensive crustal dilation accompanied the evolutiol of throughout the area. They are probably coeval with the Island Karmutsen Formation ]alas and intrusions. Deformation Intrusionswith which they are spatially related. specifically associated with this event has not yet been docu- Lithologically, they include intermediate feldspar porphyry, mented. Shear zones within gabbros, and especially along hornblende feldspar porphyry and minor diabase. their margins, may be contemporaneous or later, A suite of pale grey, fine-grained, aphyric dacite dykes of unknown age intrudes Cameron River Formation sediments PHASE 4: POST-MIDDLE JURAS8IC-PRE-LATE and Triassic gabbro in the Sansum Narrows and Genoa Bay CRETACEOUS area. he-Nanaimo Group dr:formation resulted in regional- scale warping of Vancouver Island, producing the three major geanticlinal uplifts cored by Sicker Group rocks STRUCTURE AND TECTONICS (Figure l-6-l), including the Cowichan uplift. Faulting, Southern Vancouver Island has undergone a complex tec- often axial, accompanied the folding and is most easily :=en tonic history involving at least six major deformational south of the Cowichan River in the Cowichan Lakemap area. events, often rejuvenating previous structures. The present Pre-Nanaimo Group faults are suspected north of the map pattern in the Duncan area is dominated by the effects of Cowichan River but are obscured by later events. Uplift and Late Cretaceous thrusting, though olderevents areimportant erosion followed this deformational phase, establishing the in establishing relationships within individual thrust slices. pre-Nanaimo Group topography.

PHASE 1: LATE DEVONIAN PHASE 5: LATE CRETACEOUS Syn-Sicker Groupdeformation produced large-scaleopen Large-scalewest-northwesterly trending thrusts cut the folds in the Nitinat and McLaughlin Ridge Formation vol- Cowichanuplift into several slices (Figure 1-6-4). Wlere canics in the Cowichan Lake area and the southwestem part exposed, these are high-angle reverse faults which dip be- of the Duncan map sheet. Uplift and erosion subsequent to tween 45 and 90 degrees to the north-northeast, paralleling this event are reflected by the unconformity below the Cam- the earlier axial foliation in Sicker Group rocks. Slip plms eron River Formation. are relatively sharp and nanow, though wideschistose zones have formed in receptive :lithologies. The thrusts general!y PHASE 2: POST-LOWERPERMIAN-PRE-MIDDLE place older rocks over younger and become listric at mid- TRIASSIC crustal depths (Sutherland Brown and Yorath, 1985). Dis- placements along fault planes are unknown but are probably The second deformationalevent affected all Sicker Group small, of the orderof 1 to 1,O kilometres, so as to maintain the rocks producing a series of west-northwest-trending, south- integrity of the Cowichan uplift. Direction of motion is also west-verging, asymmetric folds with abundant parasitic unknown. The regional m;lp pattern suggests movement di- minor folds. Major fold axes are often difficult to locate in rected to the west-southwest; slickensides on fault phzs the field but can be estimated fromregional patterns and the indicate latest movement was horizontaland westerly di- results of exploration drilling programs. Overturning of beds rected. Minor imbricate faults are developed along mo:it of is rarely observed. However, on the west slope of Rheinhart the thrusts, particularly where Nanaimo Group sediments Creek, a sliver of McLaughlinRidge Formation breccias occur in the footwall. occurs between Cameron River Formation sediments in an apparentlyoverturned anticline. However, thestructurally The age of thrusting is believed to be Campanian (Dom, lower sediments are right-way-up suggesting a thrust and 1986) and certainly involves the Extension-Rotection For- nappe structure is more likely. mation and possibly the Cedar District Formation along. the Chemainus River (see previous discussion of stratigraphy). Penetrative fabrics (schistosity in volcanics and cleavage in sediments) axial planar to the folds are well developed PHASE 6: ? TERTIARY throughout most of the central part of the map area. They have moderate to steep northeasterly dips. lntense flanening Several north-northeast crossfaults offset the Late !:re- normal to the foliation is observed within volcanic rocks, taceous thrusts within the Duncan area. They are all mb- whereas Cameron RiverFormation sediments behaved more vertical with downthrows KOthe west. The ageof faulting is competently and lack flattening fabrics. Lineations due to unknown, although the sinlilar trending Yellows Creek fault bedding-foliation intersections and elongationof crystals and in the Albemi area deformsa Late Eocene intrusion(Yorath, clasts are well developed. Plunges of the lineations are usu- personal communication, 1987). ally shallow, 5 to 15 degrees,and may be to the west- Regional tilting of all Vancouver Island has taken place northwest or east-southeast. Within the more schistose vol- since the Late Eocene emplacement of terranes outboard of canic rocks, a crenulation cleavage is sporadically observed Wrangellia. normal or slightly oblique to the axial schistosity. This sec- ond foliation is particularly well developedin structural depressions and culminations markedby change in azimuth METAMORPHISM of lineationsand appears to be axial to later broad open The metamorphic gradein the area is generally quite low, warps. but increases withthe ageand structural positionof the rocks. 87 Figure 1-6-4. Late Cretaceous thrust system of southem Vancouver Island with Tertiary (?) cross faults. Sicker Group outcrop areaincludes younger intrusions.

Nanaimo Group sedimentsare essentially unmetamorphosed MINERAL DEPOSITS showing only diagenetic alterations in detrital iron oxides Exploitation of the mineral resources of the Duncan area and calcareous cements.Basalts of the Kannutsen Formation has beenundertaken sincethe late nineteenth century, though show amygdule infillings and veins of chlorite, calcite, epi- originally restricted to nonmetallic deposits. The turn of the dote and quartz, and alteration assemblages typical of the century saw commencement of exploration for goldand base prehnite-pumpellyite facies. Intrusiverocks are unaltered metals,particularly inthe Chemainus Riverand Copper except in chloritic shear zones. Canyon areas. Production was limited except for three small Sediments of the CameronRiver Formationare essentially mines on Mount Sicker (Lenora,Tyee and Richard111). A lull unmetamorphosed except where involved in intense shearing in activity occurred between the world wars and all mine when chlorite and sericite develop along foliation planes. production ceased.The Twin J (Lenora) mine on Mount Volcanic rocks of the McLaughlin Ridge and Nitinat Forma- Sicker was returned to production from 1943 to 1947. Over tions in theChipman Creek to Maple Mountain belt, the next 30 yearsonly sporadic explorationactivity took however, showthe effects of greenschistfacies meta- place in the area for gold, base metals, manganese and iron morphism.The felsicvolcanics develop sericite, talcand ore. All areas of Sicker Group outcrophave since been staked chlorite along foliation planes and are interbedded with and numerous exploration targets defined by major and minor chloriteschists. Intermediate to maficrocks have junior mining companies and local prospectors. chloritic schistose matrixes with epidote alteration of feld- Several types of mineral deposit arepresent in the Duncan spars. Lithic lapilli may show almost completereplacement area (Figure 1-6-5; Table 1-6-1): by epidote. Nitinat volcanic rocks in the Banon Creek area, Volcanogenic,polymetallic massive sulphides: These however, are little altered though amygdulesare infilled with are the principal target in the Sicker Group rocks following chlorite, quartz and epidote. the success of exploration at Westmin Resources Limited’s Island Intrusion stocks often have contact metamorphic Buttle Lake mine. The massive sulphides are hosted within aureoles developed around their perimeters. Porphyroblasts the felsic volcanic tuffs of the McLaughlin Ridge Formation of chiastolite or biotite are developed in Cameron River andrestricted to a belt runningfrom ChipmanCreek to sediments aroundseveral stocks, and hornblende and pyrox- Mount Richards, in thehangingwall of the Fulford fault. ene porphyroblasts are present in Nitinat Formation lapilli Major occurrences are found on the Mount Sicker and Lara tuffs in contact with the Ladysmith stock near Holland Lake. properties. 88 On Mount Sicker, massive sulphides were discovered in tion along some faults may be several metres wide. Corn- 1898and production issued from three separate mines manly reported sulphides are pyrite, pyrrhotite, chalcop)rite (Lenora, Tyee and Richard 111) for several years. The com- and arsenopyrite. The carbonate is principally ankerite and bined property is presently under exploration by Minnova calcite. Carbonate appears to be less cotnmon to the east. Inc.(formerly CorporationFalconbridge Copper). Baritic Though numerous veins have been investigated in the pas;, laminated sulphides are located within a distinctive thinly none have proven economic potential. bedded package of intercalated siliceous argillaceous sedi- ments and tuffs up to 70 metres thick. The local stratigraphy is, however, disrupted by folding, faulting (pre-Triassic as TABLE 1-6-1. well as Late Cretaceous) and the intrusion of two thick Late MINERAL OCCURRENCIES IN THE DUNCAN MAP AREA Triassic gabbro sills. Name MinMe No. Ucrmomir Wmk Exploration by Abermin Corporation on the Lara property I. Volcanogenic plymelallic massive sulphide$ started in 1981. Volcanic rocks of the McLaughlin Ridge Ill Mount Sicker W2B-MI. W;: py, cpy, sphl. gin, ba la1 Lenom-Tyee (Twin I! Formation in the northern part of the property are thrust over lb! Rrhod 111 WZB-W3 py, cpy, spN. gln, ba a panel of Cameron River Formation sediments, late Triassic W2B-w4 py, cpy, Au. Ap gabbros and Nandimo Group sediments to the south. The W2B-037 cpy, py. Ag volcanic package contains a lower felsic tuff, a middle W2B-040 cpy, py. Au. Ag andesitic crystal-lapilli tuff and an upper felsic crystal tuff. W2BO4 cpy. Ag Significant mineralization is hosted by the lower felsic tuff at la) Camnation &ne sphl. py. cpy, gln. Au. Ai: two, possibly three, stratigraphic levels ofwhich the Corona- (b) Coronation Extensm Zanc sphl. py. cpy. gln, Au, Ag tion zone is the most promising. Mineralization consists of (ci Randy Nonh Zone sphl. py, cpy, tct disseminated and bedded (di Hope W2B-l IO cpy. py, sphl. gin, ,tu, Ap pyrite-sphalerite-chalcopyrite- 16) Fuga 0928.074 cpy gln. sphl galena within quartz crystal tuffs. Silica and carbonate are the principal gangue minerals: barite is lacking. The Corona- II Cold-kanng veins along shears tion zone has been delineated by drilling for about 2 kilo- (I)Mount Sickeram la) Key City W2B487 py, cpy metres along strike, with intersections up to 14 metres and ib) Queen Bee (Seanle! 0928488 py, Au averaging 6 metres. Low-grade sphalerite-pyrite-chal- (CI Belk 0928-089 cpy copyritemineralization is also found in the upper felsic Id) Westholme W2B-wo ?cpy crystal tuffs in whichcarbonate alteration is widespread. lei Norheart Copper &ne W2B-m py, cpy 12) Mount Richard5 area Other massive sulphide showings have been reported in (a! Cornucopia 0926-038 cpy, Au, Ag the Chipman Creek area (the Anita, MlNFlLE designation Ib! Yreka 0928-039 COY. Au. Ae 371, in Copper Canyon (Sharon,40; Copper Canyon, 86)and IC!Jane (New Ironclad1 W2B-049 cs, sphl. ic (dl Lucky Strikc WZB491 on Mount Richards (Yreka, 38; Jane [New Ironclad], 49). cpy (ti Sally 2 W2B-092 py, cpy Gold-bearing pyrite-chalcopyrite-quartz-carbonate it) Sins W2B-w6 cpy veins along shears: Many of the faults and shears cutting the (I! Copper Canyon W2BXl76 cpy. py Sicker Group and late Triassic gabbros are veined by rusty (41 Candy 092C-076 cpy, po weathering quartz-carbonate. Theage of the veining is uncer- IS) El Capitan - Landall area la! Catonwmd W2C-020 cpy, apy. erythrite. Au. 1.g tain,several events being suspected. Some veins are lb) Silverleaf W2C-OZI cpy, apy, p, Au, A! localized along the Late Cretaceous thrusts and Tertiary (?) (ci hint Pot W2C-043 cpy, Ag, Au crossfaults, but others may be older structures and mineraliz- Id1 El Capim WlC-019 cpy, Au. Ag ing events. Theveins are variable inlateral extent. and range 111. Manganese (Rhodocik) deposits up to about I metre wide, although quartz-carbonate altera- !I1 Hill 60 0928427 rhodonite (2) Rocky (Widow Creek. Cotionwood) W2C-I13 rhodonltc (I) Meade W2C-IIS rhodonite 14) Stanley Creek (Lookout Locality) W2C-I16 rhodmtc IS! Striker rhodollltc

W2B-029 mag, spec. hcrn.~aqer WlB!l31 mag. spec. hem.laqer W2B-076 mag. ~pec,]asper

W2B-I11 py, cpy 0928-111 py. cpy, p, mu W2B-lW cpy. py, po W2CO18 py. cpy. mo. mag. 10, let, L Au. Ag Figure Lh-5. Distribution 01 mineral depmsits in the Dun- 0928.028 mm 0928-093 limonite can-Chemainus Kiver area. 11) Vulcanopentc polymclallic massive 0928-120 limestone sulphides: Ill)Gold-bearing veins along shears: (111) Manganese WZB-IZb clay (rhodonite)deposits: !IVi Jabpers: IV) Coppcr~nmlybdenumvcinc 0928-110 diatomite and skarns; (VI1 Other mincral deposits. 0928-049 talc 89 Manganesedeposits: Manganese minerals havebeen re- REFERENCES ported in several places as fracture coatings or lenticular masses in the cherts of the Cameron River Formation. Rho- Armstrong, R.L., Isachsen, C. and Scott, K. (1986): Rh-Sr donite is the principal manganese mineral; manganese gar- and Sr Isotopic Study and U-Ph Dating of Vancouver nets, rhodochrosite and manganite have also been reported. Group Igneous Rocks and RelatedIsland Intrusions and All occurrences are in the aureoles of Jurassic granodiorite of the Coast Plutonic Complex andEarly Cenozoic intrusions and owe their origin to the contact metamorphism Igneous Rocks of Vancouver Island, British Columbia, of manganiferous sediments and are associated with ribbon TheUniversity of British Columbia, Unpublished chert. The protolith manganiferous sediment may have been Preprint. of a exhalative origin (Cowley, 19791, though the lack of Brandon, M.T., Orchard, M.J., F’anish, R.R., Sutherland contemporaneous volcanism in the area mitigates against Brown, A. andYorath, C.J. (1986): Fossil Ages and this. Oxidized deposits near Hill 60 were worked for man- Isotopic Dates from the Paleozoic Sicker Group and ganese ore in 1919-20, but the main potential for these and Associated Intrusive Rocks, Vancouver Island, British other deposits is for lapidary uses. Columbia, in Current Research, Part A, Geological Survey of Canada, hper 86-1A, pages 683-696. Jaspers: Jasper occurs at many stratigraphic levels within Clapp, C.H. (1912): Southern VancouverIsland, Geological the Sicker Group, principally associated with Nitinat Forma- Survey of Canada, Memoir 13, 208 pages. tion in the Banon Creek area (for example, UtahMines Limited, JRM property) and McLaughlin Ridge Formation Clapp, C.H. and Cooke, H.C. (1917): and Duncan in the Chipman Creek-Rheinhart Creek area (for example, Map-areas, Vancouver Island, Geological Survey of the Lady A [291 and Trek properties). Jasper beds are also Canada, Memoir 96, 445 pages. found within the Cameron River Formation, often associated Cowley. P. (1979): Correlation of Rhodonite Deposits on with manganese deposits, but also alone. The jasper deposits Vancouver Island and Saltspring Island, British Colum- consist of laminated hematite and magnetite in red or grey bia, Unpublished B.Sc. Thesis, The University ofBrit- chert. Several deposits were investigated in the 1950s for ish Columbia. taconite iron ore but found to be too small. Recent explora- Dom, K. (1986): The Beaufort Range Fault Zone in the tion has concentrated on the potential for the volcanic-hosted Alberni Area, Unpublished B.Sc. Thesis, The Univer- jaspers to contain gold. siry of British Columbia. Copper-molybdenum quartzveins: Sulphide-bearing Eastwood,G.E.P. (1979): Sicker Project (92Bi13; quartz veins occur in granodiorite and adjacent country rock 92C/16E),B.C. Ministry of Energy,Mines and on several properties inthe Cowichan Lake area hut aTe Petroleum Resources, Geological Fieldwork, 1978, rarelyreported from the Duncan area. However, chal- Paper 1979.1, pages 38-40.

copyrite-pyrite veining is reported in Nitinat Formation tuffs ~ (1980):Sicker Project-Mount RichardsArea at the RJ occurrence near Holland Lake, and a chalcopyrite- (92B/13E), B.C. Ministry of Energy, Mines and molybdenite-pyrrhotite-bearing skarn breccia is reported in a Petroleum Resources, Geological Fieldwork, 1979, drill hole on the ANT property on Chipman Creek. Both of Paper 1980-1, pages 49-51. these occurrences are adjacent to the Ladysmith stock as is ~ (1982) Geology of the Whitehouse Creek Area the Coronation showing described by Clapp and Cooke (92B/13f, g), B.C. Ministry of Energy, Mines and (1917). Petroleum Resources, Geological Fieldwork, 1981, Other deposits: Various nonmetallic deposits have been Paper 1982.1, pages 78-83. exploited in the Duncan area, particularly Quaternary clays for brickmaking and gravels for aggregate. Subeconomic Fyles, J.T. (1955): Geology of the Cowichan Lake Area, Vancouver Island, British Columbia, B.C. Ministry of grades of mica, talc, diatomite. limestone and limonite have Energy, Mines and Petroleum Resources, Bulletin 37, been reported in the area. 79 pages. Gunning, H.C. (1931): Buttle Lake Map-area, Vancouver ACKNOWLEDGMENTS Island, Geological Survey of Canada, Summary Report, 1930, Part A, pages 56-78. The authors acknowledge the enthusiastic and capable assistance provided byPaulette Tercierand Teresa Potter. The luras, s. Geology Of the Resources Mya staff of Ahermin Corporation and Falconbridge Limited are Falls Mine-area, Vancouver Island, British Columbia, Unpublished Ph.D. Thesis, The Universiry of British thanked for their ownness and willinelv allowing us access ~~ ~ I. - to maps, drill logs’and core. Invaluahle discussions of the Columbia. regionalgeology with AthollSutherland Brown, Chris Massey, N.W.D. and Friday, S.J. (1987): Geology of the Yorath,Tim England, Steve Juras, Cord Allenand many Cowichan Lake Area, Vancouver Island (92C/16),B.C. others have enriched this project. This season’s fieldwork Minisfry of Energy, Mines and Petroleum Resources, could not have proceeded without the cooperation of GeologicalFieldwork, 1986, Paper 1987-1,pages MacMillan-Bloedel Limited (Copper Canyon Camp), Crown 223-229. Forest Limited, British Columbia Ministry of Forests Massey, N. W.D., Friday, S.J., Tercier P.E. and Rublee V.J. (Duncan) and the Municipality of North Cowichan. This (1987): Geology of the Cowichan Lake Area, NTS manuscript was improved bythe editorial suggestions of John 92Ci16, B.C. Ministry ofEnergy, Mines andPerroleum Newell, Rosalyn Moir and Bill McMillan. Resources, Open File 1987-2. 90 Muller, J.E. (1980): The Paleozoic Sicker Group of Vancou- ern Vancouver Island: Geology and Geophysics, C:eo- ver Island, British Columbia, Geological Survey of logical Survey of Canada, Bulletin, in preparation Canada, Paper 79-30, 23 pages. Sutherland Brown, A., Yorath, C.J., Anderson, R.G. and __ (1982): Geology of Nitinat Lake Map Area, British Dom. K.(1986): Geological Mapsof Southern Vancou- Columbia, Geological Survey of Canada, Open File ver Island, LITHOPROBE 1, Geological Survev qf 821, Scale 1:125 OOO. Canuda, Open File 1.272, IO sheets. __ (1985): Geology, Victoria, British Columbia, Geo- Yole, R.W. (1963): An Early Permian Fauna from Vancollver logicalSurvey of Canada, Map 1553A, Scale Island,British Columbia, Bulletin, Conadion 1:loo 000. Petroleum Geologists, Volume II, pages 138-149. Muller, J.E. and Jeletzky, J.A. (1970):Geology of the Upper ~ (1964): A Faunal and Stratigraphic Study of Upper Cretaceous Nanaimo Group,Vancouver Island and Gulf Paleozoic Rocks of Vancouver Island, British Colum- Islands, British Columbia, Geological Survey of Can- bia, Unpublished Ph.D. Thesis, The Universit?.ofhit- ada, Paper 69-25, 77 pages. ish Columbia. SutherlandBrown, A. and Yorath, C.J. (1985): LITHOPROBE Profile Across Southern Vancouver __ ( 1969): Upper Paleozoic Stratigraphy of Vancouver Island: Geology and Tectonics, in Field Guides to Island, British Columbia, GeologicalAssociation of Geology and Mineral Deposits in the Southern Cana- Canada, Proceeding:;, Volume 20, pages 30-40. dian Cordillera, Geological Society of America, Cot- Ward, P.D. (1978): Revisions to the Stratigraphy and Bio- dilleran Section Meeting, Vancouver, B.C., May 1985. chronology of the Upper Cretaceous Nanaimo Gloup, SutherlandBrown, A. andYorath,C.J. (1987): Stratigraphy, British Columbia and Washington State, Canadiun C.S. Yorath, Editor, in, LlTHOPROBE Phase 1, South- Journal ofEarth Sciences,Volume 15, pages 405-423.

91