Regional Studies of VMS Mineralization and Potential within the EarlyJurassic Hazelton Group, British Columbia

By J.K. Mortensen1, P. Wojdak2, R. Macdonald3, S.M. Gordee1 and J.E. Gabites1

KEYWORDS: volcanogenic massive sulphide deposits,Eskay Creek, Hazelton Group, Stikinia, Early Jurassic,Bella Coola area, Whitesail Lake area, southern BabineRange, Stewart area, Forrest Kerr Creek area, Rocks toRiches program

INTRODUCTION

Eskay Creek type (ECT) volcanogenic mas sive sul -phide (VMS) de pos its within the Early and early Mid dleJu ras sic Hazelton Group are cur rently the fo cus of a con sid -er able amount of min eral ex plo ra tion ef fort be cause of their sub stan tial ton nage po ten tial and high pre cious metal con -tent. A pro ject was be gun in 2003 with the goal of iden ti fy -ing the spe cific con trols that lead to for ma tion of an ECTde posit in stead of a more typ i cal polymetallic, “Kuroko-type” VMS de posit. Both of these types of VMS de pos itsare known to ex ist within the Hazelton Group in Stikinia(Massey, 1999; Massey et al., 1999); how ever, de pos its inthe im me di ate area of Eskay Creek are the only sig nif i cantECT de pos its that have been dis cov ered thus far in Brit ishCo lum bia. Fund ing for the pro ject de rives in part from theRocks to Riches Pro gram, which is ad min is tered by the BC& Yu kon Cham ber of Mines, and by a con sor tium of min -ing and ex plo ra tion com pa nies, with match ing funds fromthe Nat u ral Sci ences and En gi neer ing Re search Coun cil ofCan ada (NSERC).

Work dur ing the 2003 and 2004 field sea sons in cluded1) a de tailed study of up per Hazelton Group strata in thenorth ern Bella Coola and south ern Whitesail Lake area insouth ern Stikinia known to host VMS oc cur rences that dis -play some ECT char ac ter is tics (Mortensen et al., 2004;Gordee et al., 2005; Mahoney et al., 2005); and 2) a re -gional in ves ti ga tion of key fea tures, such as crys tal li za tionage, geo chem is try and erup tion tem per a ture of vol ca nicrocks that host known VMS oc cur rences within theH a z e l t o n G r o u p , a s w e l l a s w a t e r d e p t h a n dpaleotopography of the im me di ate area in which the min er -al iza tion formed (Mortensen et al., 2004).

Re sults of the 2004 field work in the Bella Coola andWhitesail Lake ar eas are sum ma rized by Gordee et al.

(2005). This pa per re ports the re sults of field stud ies, aswell as U-Pb dat ing and Pb iso to pic stud ies of the HazeltonGroup and con tained min er al iza tion from sev eral parts ofStikinia, in clud ing the north ern Bella Coola and south ernWhitesail Lake ar eas, the south ern Babine Range east andsouth east of Smithers, the Homestake Ridge area south eastof Stew art, and the For rest Kerr Creek area (RDN prop erty) north of the Eskay Creek mine (Fig ure 1). Min eral oc cur -rences that have pre vi ously been in ter preted to besyngenetic (VMS) in char ac ter are pres ent in each of thesear eas.

NORTHERN BELLA COOLA ANDSOUTHERN WHITESAIL LAKE AREA

The re gional set ting and lo cal ge ol ogy of the south ernStikinia Terrane in the north ern Bella Coola and south ernWhitesail Lake area (Figure 1) are de scribed by Gordee etal. (2005) and Mahoney et al. (2005). Pre vi ous work ershave pro vided brief de scrip tions of VMS min er al iza tion atthe Nifty oc cur rence (Ray et al., 1998; Diakow et al., 2002), which is hosted in fel sic vol ca nic rocks of early Mid dle Ju -ras sic age and hence roughly age equiv a lent to the EskayCreek de posit. Other min er al iza tion pres ently knownwithin this part of Stikinia in cludes dis sem i na tions andveins of spec u lar he ma tite (lo cally as so ci ated with mi normal a chite; Gordee et al., 2005) and sev eral small chal co py -rite-bear ing quartz-vein brec cia zones in the Mt. Pres tonarea.

Lead iso to pic com po si tions de ter mined for ga lenafrom four sam ples of the Nifty min er al iza tion (Table 1) fallwithin the gen eral field of Pb iso to pic val ues for min er al -iza tion of Early to Mid dle Ju ras sic age in north west ernStikinia (‘Ju ras sic clus ter’ in Figure 2) and closely over lapthe field of Pb com po si tions from the Eskay Creek de positit self (Childe, 1996). This is con sis tent with the in ter pretedsyngenetic char ac ter of the Nifty min er al iza tion and its co -eval re la tion ship with the Eskay Creek de posit. A sin gle Pbanal y sis of chal co py rite from a min er al ized quartz-veinbrec cia from south east of Mt. Pres ton also falls within theJu ras sic clus ter, but is dis tinctly less ra dio genic than theNifty sulphides. None the less, the iso to pic com po si tionsug gests that the vein brec cias formed as part of an Early orMid dle Ju ras sic met al lo gen ic event, pos si bly anal o gous toepigenetic min er al iza tion of Early Ju ras sic age in the IskutRiver area in north west ern Stikinia.

Geo log i cal Field work 2004, Pa per 2005-1 49

1Mineral Deposit Research Unit, Earth & Ocean Sciences,UBC, Vancouver, BC

2BC Ministry of Energy and Mines, Smithers, BC3Bravo Venture Group, 1550-1185 West Georgia St., Vancouver,

BC

SOUTHERN BABINE RANGE

Sev eral min eral oc cur rences hosted by HazeltonGroup vol ca nic strata in the south ern Babine Range east ofSmithers (Figure 1) were in ter preted by Wojdak (1998) tobe po ten tially syngenetic in or i gin. Mac In tyre (1989) as -signed vol ca nic and sed i men tary strata in this area to theTelkwa and Nilkitkwa for ma tions based on over all li thol -ogy and sparse Late Sinemurian to ear li est Toarcian fos silages. This sug gests an age of ~195–180 Ma for the hostrocks to min er al iza tion; hence, syngenetic (?) min er al iza -tion in the area would ap pear to be some what older than that at Eskay Creek.

One of these pros pects (Harry Da vis; BC MINFILE093L 203, 204, 205 and 214) in cludes sev eral in di vid ualoc cur rences lo cated near the sum mit of Mt. Harry Da vis,north of Hous ton. It con sists mainly of dis sem i nated andfrac ture-fill ing sphalerite, chal co py rite, ga lena and lo callyflu o rite, al though, in one in stance (the “Hill top show ing”),sphalerite oc curs as dis sem i na tions along bands in mas siveto lam i nated chert. The up per por tion of Mt. Harry Da vis isun der lain by a thick sec tion of flow-banded, quartz- and

feld spar-phyric rhy o lite that is as so ci ated with bed ded redand ma roon lapilli tuffs which lo cally con tain accretionarylapilli. A sam ple of the rhy o lite is calc-al ka line in com po si -tion, with a vol ca nic-arc sig na ture (Mortensen et al., 2004). Four frac tions of zir con re cov ered from a sam ple of themas sive rhy o lite give con cor dant anal y ses (Table 2; Fig ure3a), and the old est two con cor dant anal y ses (C and E, Fig -ure 2a) give over lap ping 206Pb/238U ages of 179.3 ± 0.8 Ma(Late Toarcian), which is taken as the crys tal li za tion age ofthe sam ple. This age is near the up per age limit for Hazelton Group strata that had been rec og nized in this area on the ba -sis of fos sil age con straints. It is also sim i lar to the age of the Salmon River For ma tion that hosts the Eskay Creek de -posit; how ever, the rhy o lite at Mt. Harry Da vis isgeochemically dis tinct from that at Eskay Creek(calcalkaline vs. tholeiitic).

The Lakeview pros pect (BC MINFILE 093L 030), lo -cated ap prox i mately 6 km north east of the Harry Da vis oc -cur rence, was vis ited briefly dur ing 2004. Min er al iza tioncom prises me dium- to coarse-grained, mas sive to crudelybanded spec u lar he ma tite, chal co py rite, py rite andsphalerite. It ap pears to be roughly stratabound, and as so ci -

50 Brit ish Co lum bia Geo log i cal Sur vey

Fig ure 1. Dis tri bu tion of Early and Mid dle Ju ras sic vol ca nic and sed i men tary strata of the Hazelton Group within the Stikine Terrane ofBrit ish Co lum bia.

ated with a limy ho ri zon within steeply north west-dip pingfel sic pyroclastic rocks (Wojdak, 1998). The im me di atewallrocks for the sulphides are strongly hematized andepidotized. The over all char ac ter of the min er al iza tion, in -clud ing the min er al ogy, rel a tively coarse grain size of thesulphides, and as so ci a tion with car bon ate rocks, is mostrem i nis cent of a skarn, al though the pos si bil ity that the oc -cur rence com prises Early or Mid dle Ju ras sic syngenetic (?)min er al iza tion that has been strongly recrystallized in thecon tact au re ole of a youn ger in tru sion (not pres ently ex -posed) can not be ruled out.

One day was spent ex am in ing and sam pling the Ascotpros pect (BC MINFILE 093L 024), which com prises sev -eral in di vid ual oc cur rences near the head of Can yon Creek,ap prox i mately 30 km east of Smithers (Fig ure 1). The prop -erty is un der lain by a pack age of mixed sed i men tary rocks(mainly thinly bed ded lime stone, car bo na ceous argilliteand ar gil la ceous wacke) and in ter me di ate to fel sic brec cias,

all of which are cut by widely spaced an de site dikes. Therock units in this area have been vari ably de formed, andweaker lithologies (e.g., lime stones and argillites) show amod er ate to strong fo li a tion and lo cally abun dant mi norfold ing (e.g., Fig ure 4a). Two dis tinct styles of min er al iza -tion were ob served: 1) dis sem i na tions and bed ding-par al lel string ers of fine-grained sphalerite and ga lena in im pure ar -gil la ceous lime stones, and 2) ga lena in fine quartz string ersand dis sem i na tions in a fel sic brec cia unit (Fig ure 4b). Themin er al ized string ers in this lat ter style of min er al iza tionare trun cated at the mar gins of the clasts, in di cat ing that thevein ing pre dated brecciation and the min er al iza tion there -fore must be broadly syngenetic with re spect to the fel sicvol ca nic event.

Lead iso to pic com po si tions have been de ter mined forsul phide sam ples from all of the po ten tially syngenetic oc -cur rences in the south ern Babine Range and are shown inFig ure 2. Al though there is some scat ter in the data, all anal -

Geo log i cal Field work 2004, Pa per 2005-1 51

Error Error Error Error Error Error

(abs.) (%) (abs.) (%) (abs.) (%)

Nifty sl 18.8094 0.0277 0.15 15.6009 0.0238 0.15 38.543 0.0647 0.17

03M-01 Nifty py 18.8018 0.0082 0.04 15.6131 0.0102 0.07 38.5262 0.0334 0.09

03M-01a Nifty py 18.8107 0.013 0.07 15.5789 0.0109 0.07 38.3262 0.0435 0.11

03M-01a Nifty py 18.8089 0.0155 0.08 15.6075 0.0116 0.07 38.4445 0.0486 0.13

03M-05 cp 18.7266 0.0093 0.05 15.5958 0.0108 0.07 38.4479 0.0352 0.09

Del Santo-1 py 18.6942 0.0106 0.06 15.592 0.0108 0.07 38.3059 0.0373 0.1

Lakeview 2 py 18.8699 0.0184 0.1 15.6703 0.0158 0.1 38.6114 0.0737 0.19

Lakeview-2 py 18.8329 0.0104 0.05 15.5823 0.0105 0.07 38.4059 0.0397 0.1

Lakeview-3 py 18.7949 0.0104 0.06 15.5978 0.011 0.07 38.4427 0.0365 0.09

Su py 18.7183 0.0226 0.12 15.6213 0.0142 0.09 38.2534 0.0634 0.17

Su py 18.7529 0.012 0.06 15.6406 0.0122 0.08 38.4829 0.0385 0.1

HD py 18.7918 0.0141 0.07 15.6642 0.0138 0.09 38.6877 0.0415 0.11

Ascot sl 18.7192 0.0286 0.15 15.6187 0.0206 0.13 38.3998 0.0743 0.19

Del Santo-2 py 18.6965 0.0185 0.1 15.5905 0.0152 0.1 38.2679 0.0548 0.14

03M-100 Myborg adit gl 18.9478 0.0083 0.04 15.6773 0.0102 0.07 38.7255 0.0337 0.09

03M-101 Myborg adit cp 18.8793 0.0228 0.12 15.6657 0.0104 0.07 38.5461 0.0553 0.14

03M-101 Myborg adit cp 18.8166 0.0262 0.14 15.5736 0.0227 0.15 38.4641 0.0617 0.16

03M-102 Myborg adit cct 19.8714 0.0526 0.26 15.6951 0.0418 0.27 39.2944 0.1085 0.28

03M-105 vein in seds

adjacent to South

Dome rhyolite

cp 18.9611 0.0141 0.07 15.6418 0.0118 0.08 38.647 0.0419 0.11

03M-107a Dilly Zone py 18.7506 0.0112 0.06 15.625 0.0111 0.07 38.7768 0.0376 0.1

03M-108 Dilly Zone gl 18.9137 0.0084 0.04 15.6255 0.0102 0.07 38.5199 0.0337 0.09

03M-110 Dilly Zone gl 18.9072 0.0086 0.05 15.6089 0.0103 0.07 38.5437 0.0342 0.09

03M-111 Dilly Zone gl 18.9535 0.0082 0.04 15.6692 0.0102 0.06 38.7193 0.0335 0.09

Vanguard Cu cp 18.9132 0.0261 0.14 15.6552 0.0182 0.12 38.5787 0.0718 0.19

Vanguard Cu cp 18.9158 0.0094 0.05 15.6362 0.0107 0.07 38.5963 0.0351 0.09

Silver Crown py 19.1597 0.0115 0.06 15.6415 0.0109 0.07 38.6905 0.0376 0.1

RDN01-19 94.0 gl 18.826 0.0294 0.16 15.6883 0.0247 0.16 38.506 0.0687 0.18

RDN01-20 gl 18.8837 0.0091 0.05 15.612 0.0104 0.07 38.5669 0.0345 0.09

RDN99-01 py 18.8383 0.0094 0.05 15.6051 0.0102 0.07 38.4062 0.0349 0.09

RDN Property

All errors given at the 2 sigma level.

208Pb/204Pb

Northern Bella Coola/southern Whitesail Lake area

Southern Babine Range

Homestake Ridge

Occurrence Mineral 206Pb/204Pb 207Pb/204Pb

TABLE 1. PB ISOTOPIC COMPOSITIONS OF SULPHIDE MINERALS FROM OCCURRENCES IN THENORTHERN BELLA COOLA–SOUTHERN WHITESAIL LAKE AREA AND SOUTHERN BABINE RANGE.

y ses fall within the ‘Ju ras sic clus ter’, sug gest ing that min -er al iza tion in all cases is of Early or Mid dle Ju ras sic age. Inpar tic u lar, three anal y ses from the Lakeview pros pect over -lap com pletely with anal y ses from the Nifty oc cur rence.These re sults are some what sur pris ing, es pe cially be causethe min er al iza tion at the Del Santo pros pect (BC MINFILE093L-025) has been in ter preted by most pre vi ous work ersas a skarn, pos si bly as so ci ated with an Early Ter tiary diorite in tru sion on the prop erty (M. Marchand, pers. comm.,2004).

HOMESTAKE RIDGE AREA

The Homestake Ridge prop erty, ap prox i mately 32 kmsouth east of Stew art (Fig ure 1), which is cur rently be ingex plored by the Bravo Ven tures Group Inc., com prises over 80 in di vid ual base and pre cious metal oc cur rences. Theprop erty is un der lain by a Late Tri as sic to Early and Mid dle(?) Ju ras sic pack age of ba saltic, andesitic and rhyolitic vol -ca nic and volcaniclastic and clastic sed i men tary rocks (Fig -ure 5). The prop erty hosts more than 80 in di vid ual min eraloc cur rences, some of which have been worked since 1914.Pre vi ous work on the prop erty by Noran da Ex plo ra tionLtd. and TeckCominco Ltd. iden ti fied sev eral highly pro -spec tive tar gets, in clud ing shear-hosted veins host ing high-grade pre cious met als, broad ar eas of gold-en riched,quartz-seri cite-py rite min er al iza tion with bulk ton nage po -ten tial, and a vol ca nic-sed i men tary stra tig ra phy with pre -cious metal–enriched VMS po ten tial.

Hazelton Group rocks on the prop erty con sist of ba -saltic, andesitic and dacitic vol ca nic and volcaniclasticrocks that are equated to the Early Ju ras sic Betty Creek For -

ma tion, as well as fine-grained clasticsed i men tary rocks that may cor re latewith the early Mid dle Ju ras sic SalmonRiver For ma tion. Min er al iza tion and al -ter ation is fo cused around subvolcanichornblende-feld spar por phyry in tru -sions that re sem ble and are be lieved tobe equiv a lent in age to the Goldslide in -tru sions at Red Moun tain, lo cated ap -prox i mately 25 km north east of theprop erty (Rhys et al., 1995). These por -phyry in tru sions oc cur along struc turalbreaks in the rock pack age and are as so -ci ated with broad ar eas of rocks with lo -cally in tense seri cite-quartz-py rite al -teration. Two large ac cu mu la tions offlow-banded rhyolitic volcanics, tuffand coarse fragmental rocks are pres enton the prop erty and are re ferred to as theNorth Dome and South Dome. The fel -sic units were pre vi ously equated withthe Mt. Dilworth For ma tion, whichserved to high light the po ten tial of theprop erty for ECT-type VMS min er al iza -tion.

The prop erty dis plays a rel a tivelycom plex struc tural his tory. North west-and north east-trending fault-bound rifts

ap pear to have con trolled the de po si tion of the Early Ju ras -sic se quence and lo cal ized the em place ment of por phyryin tru sions. Large-scale, south west-di rected, open to iso cli -nal, disharmonic folds and thrusts likely formed in the Cre -ta ceous, but were strongly con trolled by the ear lier ba singe om e try. East-west ex ten sion and dextral strike-slip fault -ing of prob a ble Ter tiary age pro duced block fault ing andmi nor lat eral off sets on nu mer ous, highly vis i ble, north -east-trending fault struc tures.

The Homestake Ridge prop erty hosts a very largenum ber of pre cious and base min eral oc cur rences. Min er al -iza tion is typ i cally struc tur ally con trolled, with some of theoc cur rences hav ing a close spa tial as so ci a tion with vari -ably al tered hornblende-feld spar por phyry. Brief de scrip -tions of some of the in di vid ual oc cur rences shown on Fig -ure 5 are given here to high light the di verse na ture ofmin er al iza tion pres ent.

The Homestake Crown Grant area cov ers an epi ther -mal vein sys tem hosted by an up per unit of mas sive tocoarse fragmental andesitic volcanics and lower units ofheterolithic to mono lithic de bris flows, dacitic fragmentalsand feld spar-hornblende por phyry, and andesitic to daciticvol ca nic rocks. High-grade gold-sil ver shoots are lo cal ized near the in ter sec tion of the main min er al ized shears. Min er -al iza tion is hosted within pyritiferous quartz stockworksand brec cias with trace to sev eral per cent chalopyrite,sphalerite and ga lena in a hostrock that is in tensely al teredto seri cite and K-feld spar. Drill ing dur ing 2003 in ter sectedbroad zones (up to 43 m thick) of highly anom a lous gold(0.7 g/t) and sil ver (10.2 g/t) min er al iza tion with sev eral>1 m wide in ter vals of 6–13.9 g/t Au and up to 2 oz./t Ag.

52 Brit ish Co lum bia Geo log i cal Sur vey

Fig ure 2. Lead iso to pic com po si tions of sul phide min er als from oc cur rences in the north -ern Bella Coola–south ern Whitesail Lake area and south ern Babine Range. Fields for Ju -ras sic and Ter tiary sul phide Pb com po si tions are from Rhys et al. (1995). Field for EskayCreek sul phide Pb com po si tions is from Childe (1996).

Geo log i cal Field work 2004, Pa per 2005-1 53

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Cal cite-bar ite veins ex posed in his tor i cal trenches atthe Van guard gold show ing run up to 9.56 g/t Au and10.5 g/t Ag over 6.0 m. The zone dips steeply to the north -east and can be traced on sur face for about 200 m.

The Dilly and Dilly west zones com prise a se ries ofnorth-north west–trending pre cious and base metal min eraloc cur rences that form two subparallel lin ear trends withstrike lengths of 1500 m and 600 m, re spec tively. The oc -cur rences are found at or near the con tact be tween a fel sicvol ca nic pack age and a bed ded, fine-grained clastic suc ces -

sion. Styles of min er al iza tion in clude mas sive sul phide

base metal show ings, semimassive to mas sive ar seno py rite

show ings, mas sive lam i nated ga lena-sphalerite show ings

and sul phide stockworks wi thin fel s ic vol ca nic

pyroclastics. Bravo Ven ture ge ol o gists in ter preted the

west ern rhy o lite-sed i men tary con tact as pre dom i nantly a

struc tural fea ture with min er al iza tion oc cur ring in north -

west- to west-north west-di rected shears along the con tact

zone.

54 Brit ish Co lum bia Geo log i cal Sur vey

Fig ure 3. U-Pb con cordia plots for zir cons from fel sic vol ca nic and plutonic rocks.

In the south end of the Dilly zone, ga lena-rich, bandedmas sive sul phide min er al iza tion was ob served in sev eralsur face oc cur rences along a 300 m strike length. This min -er al iza tion is hosted in a chlorite-sericite–altered fel sic vol -ca nic rock and in cludes a 6–10 cm wide zone of mas sive ga -lena and sphalerite.

The Sil ver Crown oc cur rence is lo cated within a sed i -ment-sill com plex and is marked by a col lapsed adit in ar -gil la ceous sed i men tary rocks. Mas sive sphalerite-ga lena-(tetrahedrite) sul phide boul ders oc cur in a waste pile nearthe mouth of the adit. Sam pling of the boul ders byTeckCominco Ltd. re turned val ues of up to 14.15 g/t Au,5740 g/t Ag, 11.55% Pb and 3.3% Zn. Min er al iza tion can -not be traced be yond the im me di ate vi cin ity of the adit.

Lead iso tope anal y ses were car ried out on a num ber ofsam ples from sev eral of the zones of min er al iza tion on theRDN prop erty. All but one of the anal y ses fall well withinthe field of com po si tions for Early and Mid dle Ju ras sicmin er al iza tion in north west ern Brit ish Co lum bia (Fig ure6). The only ex cep tion is ga lena from the Ag-rich Sil verCrown vein, which yields a com po si tion that falls withinthe Ter tiary clus ter of iso to pic com po si tions (Fig ure 6).This in di cates that at least some of the Ag-rich veins in thearea rep re sent an Early Ter tiary met al lo gen ic event thatover prints the main Early and Mid dle Ju ras sic min er al iza -tion.

A sam ple of the South Dome rhy o lite (Fig ure 5) wassam pled for U-Pb zir con dat ing. This body ap pears to be in -tru sive into dacite and ba salt, as well as fine-grained sed i -men tary rocks that were thought to be part of the HazeltonGroup. Three frac tions of zir con from the South Domesam ple were an a lyzed. Two fall on or near con cordia atabout 219 Ma and a third anal y sis falls well to the right ofcon cordia, in di cat ing the pres ence of a sig nif i cant in her ited zir con com po nent (Fig ure 3b). A re gres sion through thethree anal y ses yields cal cu lated lower and up per in ter ceptages of 219.7 ± 1.0 Ma and 2.85 Ga, in di cat ing a Late Tri as -sic (early Norian) crys tal li za tion age and Late Archean in -her i tance. This re sult is very sur pris ing, since it in di cates

that at least some of the strati graphic units on theHomestake Ridge prop erty ac tu ally form part of the Stuhini Group rather than the Hazelton Group. The im pli ca tions ofthis age for the struc ture and stra tig ra phy on the prop ertyare still be ing as sessed.

FORREST KERR CREEK AREA

The RDN prop erty of Rimfire Min er als Corp. (BCMINFILE 104G 144; Fig ure 1), lo cated in the For est KerrCreek area ap prox i mately 40 km north east of the EskayCreek mine, cov ers a pack age of fel sic vol ca nic rocks over -lain by mafic vol ca nic rocks and car bo na ceous argillitesthat are thought to cor re late, at least in part, with the earlyMid dle Ju ras sic Salmon River For ma tion that hosts theEskay Creek de posit (Fig ure 7) Al though most of the min -er al iza tion lo cated on the prop erty thus far con sists of struc -tur ally con trolled min er al ized veins and brec cias, strongpre cious and base metal geo chem i cal anom a lies withinargillite sec tions are very rem i nis cent of that as so ci atedwith ECT min er al iza tion. Di a mond-drill ing has in ter sected a thick sec tion of dacitic to rhyolitic flows, domes andvolcaniclastic rocks in the stratigraphically lower part ofthe sec tion.

Three fel sic units from the lower fel sic se quence weredated us ing con ven tional U-Pb zir con meth ods. Sam pleRDN-01-16-85.34m is a weakly fo li ated, very stronglysericitized and clay-al tered K-feld spar–phyric monzonitefrom the Bound ary Zone in the south ern part of the RDNprop erty (Fig ure 7). Five strongly abraded frac tions of zir -con were an a lyzed (Ta ble 2; Fig ure 3c). Four of these frac -tions give over lap ping con cor dant anal y ses with a to talrange in 206Pb/238U ages of 193.6 ± 0.5 Ma, which is takenas the crys tal li za tion age of the sam ple. The fifth frac tionfalls slightly be low the con cordia and ap pears to have suf -fered mi nor Pb loss. A sec ond sam ple (RDN-01-19-94.0m)con sists of mas sive, plagioclase-phyric por phyry of the‘Gos san Creek por phyry’ unit from near the north ern end of the Wedge Zone (Fig ure 7). The por phyry is strongly car -

Geo log i cal Field work 2004, Pa per 2005-1 55

Fig ure 4. Min er al ized spec i mens from the Ascot oc cur rence: A) de formed ar gil la ceous lime stone and dis sem i nated ga lena; B) fel sicfragmental rocks with fine, ga lena-bear ing quartz string ers that pre date brecciation and de po si tion.

56 Brit ish Co lum bia Geo log i cal Sur vey

Fig ure 5. Sim pli fied ge ol ogy of the Homestake Ridge prop erty (cour tesy of TeckCominco Ltd.).

bon ate al tered and con tains abun dantfine string ers of car bon ate. Three frac -tions of abraded zir con yield con cor dantanal y ses but with some scat ter along thecon cordia (Fig ure 3d). The best es ti mate for the crys tal li za tion age of this sam pleis con sid ered to be given by the to talrange of 206Pb/238U ages for the old esttwo con cor dant frac tions, at 193.0 ±1.3 Ma. Frac tion E has suf fered mi norPb loss and frac tion A ap pears to con taina mi nor com po nent of older, in her itedzir con. The third sam ple (RDN-01-20-23.2m) was from mas sive feld spar-phyric dacite from the cen tral part of theWedge zone (Fig ure 7). Three frac tionsof strongly abraded zir con were an a -lyzed. All three anal y ses fall on or nearcon cordia (Fig ure 3e), and the best es ti -mate for the crys tal li za tion age of thesam ple is given by the old est 206Pb/238Uage of 193.6 ± 1.1 Ma.

These new data in di cate that thelower fel sic vol ca nic pack age on theRDN prop erty is Late Sinemurian in ageand thus sig nif i cantly older than ei therthe Eskay rhy o lite or the footwall dacite in the im me di ateEskay area. Fos sil ages from lo cally tuffaceous argillite inthe over ly ing argillite-ba salt se quence in the vi cin ity of theRDN range from Toarcian to as young as Bathonian (Lo gan et al., 2000), in di cat ing that strata that are age equiv a lent tothe Salmon River For ma tion in the Eskay Creek area are in -deed pres ent on the RDN prop erty. These re sults raise thepos si bil ity that a sig nif i cant un con formity may sep a rate the lower fel sic pack age from the over ly ing argillite-ba salt se -quence in the RDN area.

Three sam ples of ga lena from cross cut ting veinlets inargillite in drillcore on the RDN were an a lyzed for Pb iso -tope com po si tion. All three anal y ses fall well within thefield of Ju ras sic Pb dates (Fig. 6), con firm ing that theepigenetic min er al iza tion in this area is part of the Early toMid dle Ju ras sic min er al iz ing event in north west ern Brit ishCo lum bia.

DISCUSSION AND CONCLUSIONS

Re sults of the study pro vide new con straints on the na -ture of base and pre cious metal min er al iza tion within theHazelton Group in sev eral parts of Stikinia, and spe cif i -cally on the po ten tial for some of the known oc cur rences torep re sent ECT min er al iza tion. The Nifty oc cur rence in theBella Coola map area closely re sem bles Eskay Creek interms of age and Pb iso to pic com po si tion, al though thegeo chem is try of the hostrocks at Nifty is calcalkaline as op -posed to the tholeiitic hosts for the Eskay Creek de posit it -self. Al though the Nifty shares some of the geo chem i caltraits of ECT min er al iza tion (Ray et al., 1998; Diakow etal., 2002) it does not ap pear to have the strong gold en rich -ment that is seen at Eskay Creek. The only other min er al iza -

tion iden ti fied thus far within the Hazelton Group sec tion in north ern Bella Coola and south ern Whitesail Lake map ar -eas con sists of small, chal co py rite-bear ing quartz-veinbrec cias. Lead iso to pic com po si tions of this style of min er -al iza tion in di cate that it also rep re sents part of an Early orMid dle Ju ras sic met al lo gen ic event, and is not re lated toEarly Cre ta ceous and youn ger in tru sions in the area. De -spite the lim ited ev i dence for ad di tional VMS oc cur renceswithin the Hazelton Group in this area, wide spreadsemiconformable epidote al ter ation within the sec tion, as -so ci a tion with a co eval subvolcanic (?) fel sic in tru sion andthe pres ence of sig nif i cant synvolcanic fault struc tures(Gordee et al., this vol ume; Mahoney et al., this vol ume)sug gest that the area has very high po ten tial for host ing ad -di tional VMS oc cur rences.

The na ture and age of sev eral min eral oc cur rences inthe south ern Babine Range that were iden ti fied by Wojdak(1998) as pos si ble VMS tar gets re mains par tially un re -solved. Lead iso to pic com po si tions from all of the oc cur -rences are con sis tent with an Early or Mid dle Ju ras sic ageof min er al iza tion; how ever, at least two of the oc cur rences(Del Santo and Lakeview) ap pear in the field to be ei therskarns or pos si bly syngenetic min er al iza tion that has beenstrongly recrystallized and over printed in the con tact au re -ole of in tru sions. At least some of the min er al iza tion at theAscot oc cur rence pre dates brecciation and sub se quent de -po si tion of fel sic vol ca nic units, and must there fore bebroadly syngenetic. Al though none of the var i ous styles ofmin er al iza tion at the Harry Da vis oc cur rence is con clu -sively syngenetic in char ac ter, a U-Pb age of 179.3 ± 0.8 Ma for a flow-banded rhy o lite unit in di cates that vol ca nicrocks in this area are age equiv a lent to the Salmon RiverFor ma tion that hosts the Eskay Creek de posit.

Geo log i cal Field work 2004, Pa per 2005-1 57

Fig ure 6. Lead iso tope com po si tions of sul phide min er als from oc cur rences in theHomestake Ridge area and from the RDN prop erty. Fields for Ju ras sic and Ter tiary sul -phide Pb com po si tions are from Rhys et al. (1995). Field for Eskay Creek sul phide Pbcom po si tions is from Childe (1996)

M i n e r a l i z a t i o n i n t h eHomestake Ridge area is mainlystruc tur ally con trolled and many oc -cur rences have a close spa tial as so -ci a tion with hornblende-feld sparpor phyry dikes and sills of pre -sumed Early Ju ras sic age. These oc -cur rences yield Pb iso to pic com po -si tions that are con sis tent with anEarly or Mid dle Ju ras sic age, andthis style of min er al iza tion ap pearsto be anal o gous to that at the RedMoun tain and/or Silbak Pre mier de -pos its to the north and west. OtherAg-rich vein oc cur rences such asSil ver Crown have Pb iso to pic com -po si tions that in di cate they are EarlyTer tiary in age and rep re sent a youn -ger, su per im posed met al lo gen icevent.

The Late Tri as sic U-Pb zir conage re ported here for the SouthDome rhy o lite in di cates that not allof the supracrustal units in theHomestake Ridge area be long to theHazelton Group, but at least some ofthem are part of the un der ly ingStuhini Group. This sug gests thatthere may be ma jor, pre vi ously un -rec og nized struc tural com plex i tiesin this re gion. None of the min er al -iza tion in the Homestake Ridge areahas been proven to be syngenetic;how ever, VMS min er al iza tion doesoc cur at the Sault oc cur rence (BCMINFILE 103P 233), ap prox i -mately 6 km east of the HomestakeRidge prop erty. The Sault oc cur -rence is hosted within fel sic vol ca -nic rocks that have given a U-Pb zir -con age of 193.5 ± 0.4 Ma (Late Sinemurian; Mortensenand Kirkham, 1992), and is one of sev eral Ag-rich VMS oc -cur rences that have been iden ti fied in the up per KitsaultRiver val ley (e.g., Dolly Var den, Torbrit; Pinsent, 2001).The Sault oc cur rence is there fore ap prox i mately equiv a lent in age to some of the in ter me di ate-com po si tion ma roon and green vol ca nic brec cias that un der lie parts of theHomestake Ridge prop erty and are thought to cor re latewith the Betty Creek for ma tion, as rec og nized far ther to thenorth (Lewis and Tosdal, 2001). There does ap pear to besome po ten tial for VMS min er al iza tion on the HomestakeRidge prop erty, al though it would likely be at a lower strati -graphic level than that at the Eskay Creek de posit.

Stud ies of the RDN prop erty in the For rest Kerr Creekarea sup port the sug ges tion that geo chem i cal anom a liesand scat tered base and pre cious metal oc cur rences there are po ten tially close an a logues of the Eskay Creek de posit.Fel sic vol ca nic and volcaniclastic rocks that make up thelower part of the strati graphic se quence on the RDN prop -erty are ~193 Ma in age, and there fore equiv a lent in age to

host rocks for the Sault VMS oc cur rence (see dis cus sionabove). Lam i nated py rite was in ter sected in one drillholewithin this pack age of fel sic rocks on the RDN prop erty (M. Jones, pers. comm., 2004), sug gest ing that an older VMSho ri zon may be pres ent on the prop erty. Most of the geo -chem i cal anom a lies that are thought to be more anal o gousto the Eskay Creek de posit on the RDN oc cur within theover ly ing argillite-ba salt pack age, which con tains fos silsindicating that the units are cor re la tive with the SalmonRiver For ma tion.

ACKNOWLEDGMENTS

We thank Graeme Ev ans of TeckCominco Ltd. formany in sights and dis cus sions re gard ing the HomestakeRidge prop erty ge ol ogy. We also thank Rich ard Fried manat the Pa cific Cen tre for Iso to pic and Geo chem is tryResearch for crit i cal as sis tance in pro duc ing the U-Pb datare ported here, and for pro vid ing a crit i cal re view of themanu script.

58 Brit ish Co lum bia Geo log i cal Sur vey

Fig ure 7. Sim pli fied ge ol ogy of the RDN prop erty (from Rimfire Min er als Cor po ra tionwebsite, http://www.rimfire.bc.ca/Home.asp).

REFERENCES

Childe, F. (1996): U-Pb geo chron ol ogy and Nd and Pb iso topechar ac ter i s t ics of the Au-Ag-rich Eskay Creekvolcanogenic mas sive sul fide de posit, Brit ish Co lum bia;Eco nomic Ge ol ogy, Vol ume 91, pages 1209–1224.

Diakow, L.J., Mahoney, J.B., Gleeson, T.G., Hrudey, M.G.,Struik, L.C. and John son, A.D. (2002): Mid dle Ju ras sicstra tig ra phy host ing volcanogenic mas sive sul phide min -er al iza tion in east ern Bella Coola map area (NTS 093/D),south west Brit ish Co lum bia; in Geo log i cal Field work2001, BC Min is try of En ergy, Mines and Pe tro leum Re -sources, Pa per 2002-1, pages 119-134.

Lewis, P.D. and Tosdal, R.M. (2000): Metallogenesis of the IskutRiver area, north west ern Brit ish Co lum bia; Min eral De -posit Re search Unit, Spe cial Pub li ca tion No. 1, 337 pages.

Lo gan, J.M., Drobe, J.R. and McClelland, W.C. (2001): Ge ol ogyof the For rest Kerr–Mess Creek area, north west ern Brit ishCo lum bia (NTS 104B/10, 15 & 104G/2 & 7W); BC Min is -try of En ergy, Mines and Pe tro leum Re sources, Bul le tin104, 163 pages.

Mac In tyre, D.G., Desjardins, P. and Tercier, P. (1989): Ju ras sicstrati graphic re la tion ships in the Babine and Telkwaranges (93L/10, 11, 14, 15); in Geo log i cal Field work1988,BC Min is try of En ergy, Mines and Pe tro leum Re -sources, Pa per 1989-1, pages 195–208.

Massey, N.W.D. (1999): Volcanogenic mas sive sul phide de pos its in Brit ish Co lum bia; BC Min is try of En ergy and Mines,Open File 1999-2.

Massey, N.W.D., Alldrick, D.J. and Lefebure, D.V. (1999): Po -ten tial for sub aque ous hot-spring (Eskay Creek) de pos itsin Brit ish Co lum bia; BC Min is try of En ergy and Mines,Open File 1999-14.

Mortensen, J.K. and Kirkham, R. (1992): A U-Pb zir con age forhost rocks of a syngenetic stron tium (-zinc) oc cur rence inthe Kitsault Lake area, west-cen tral Brit ish Co lum bia;Geo log i cal Sur vey of Can ada, Pa per 91-2, pages 118–185.

Mortensen, J.K., Gordee, S.M., Mahoney, J.B. and Tosdal, R.M.(2004): Re gional stud ies of Eskay Creek–type and othervolcanogenic mas sive sul phide min er al iza tion in the up -per Hazelton Group in Stikinia: pre lim i nary re sults; inGeo log i cal Field work 2003, BC Min is try of En ergy, Mines and Pe tro leum Re sources, Pa per 2004-24, pages 249–262.

Pinsent, R.H. (2001): Min eral de pos its of the Up per KitsaultRiver area, Brit ish Co lum bia (103P/W); in Geo log i calField work 2000, BC Min is try of En ergy, Mines and Pe tro -leum Re sources, Pa per 2001-1, pages 313–326.

Ray, G.E., Brown, J.A., Fried man, R.M. and Cornelius, S.B.(1998): Ge ol ogy of the Nifty Zn-Pb-Ba pros pect, BellaCoola dis trict, Brit ish Co lum bia; in Geo log i cal Field work1997, BC Min is try of en ergy, Mines and Pe tro leum Re -sources, Pa per 1998-1, pages 20-1–20-28.

Rhys, D.A., Sieb, M., Frostad, S.R., Swanson, C.L., Prefontaine,MA., Mortensen, J.K. and Smit, H.Q. (1995): Ge ol ogy and set ting of the Red Moun tain gold-sil ver de posit, north -west ern Brit ish Co lum bia; in Schroeter, T.G., Por phyryDe pos its of the North west ern Cor dil lera of North Amer -ica, Ca na dian In sti tute of Min ing and Met al lurgy, Spe cialVol ume 46, pages 811–828.

Wojdak, P. (1998): Volcanogenic mas sive sul phide de pos its in the Hazelton Group, Babine Range, BC; BC Min is try of En -ergy, Mines and Pe tro leum Re sources, Ex plo ra tion andMin ing in Brit ish Co lum bia 1998, pages C1–C13.

Geo log i cal Field work 2004, Pa per 2005-1 59

60 Brit ish Co lum bia Geo log i cal Sur vey