Conclusions

�

�

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Gold veins precipitated from H O-CO -NaCl fluids.

Temperatures and pressures of vein formation range from300 °C at 1.5 kilobars to just under 500 °C at 3.5 kilobars.

Gold mineralization dated at approximately 36 Ma.

Gold fineness is approximately 23 weight percent Ag.

Resetting or disequilibrium of the S isotopes in the mainsulphide phases.

NE trending quartz-carbonate-arsenopyrite vein swarms.

Minor base-metal sulphides within the veins.

Proximity to extensive limestone units cut by the EoceneMount Washington instrusive suite and associated adakites.

Pseudo "brittle-ductile" structures in the quartz-carbonate-arsenopyrite veins.

2 2

Exploration Guidelines

References

DeBari, S.M., Anderson, R.G. and Mortensen, J.K. (1999): Correlationamong lower to upper crustal components in an island arc: TheJurassic Bonanza arc, Vancouver Island, Canada. CanadianJournal of Earth Sciences, Volume 36, 1371-1413.

Hansen, M.C. and Sinclair, A.J. (1984): A preliminary assessment ofZeballos mining camp (92L). Geological Fieldwork, 1983. BritishColumbia Geological Survey, 219-232.

Jaffey, A.H., Flynn, K.F., Glendenin, L.E., Bentley, W.C. and Essling, A.M.(1971): Precision measurement of half-lives and specificactivities of U and U . Physical Review 4, 1889-1906.

Massey, N.W.D. (1995): Geology and mineral resources of the AlberniNanaimo Lakes sheet, Vancouver Island, 92 F/1W, 92 F/2E andpart of 92 F/7E. British Columbia Ministry of Energy Mines andPetroleum Resources, Geological Survey Branch Paper 1992-2, 132 pages.

Muller, J.E., Cameron, B.E.B., And Northcote, K.E. (1981): Geology andMineral Deposits of Nootka Sound map-are, Vancouver Island,British Columbia; Geological Survey of Canada, Paper 80-16,53p.

Muller, J.E. and Carson, D.J. (1969): Geology and mineral deposits ofAlberni map-area, British Columbia, (92F); Geological Survey ofCanada, Paper 68-50, 52 pages.

Sinclair, A.J. and Hansen, M.C. (1983): Resource assessment of gold-quartz veins, Zeballos mining camp, Vancouver Island; apreliminary report (92L). Geological Fieldwork, 1982. BritishColumbia Geological Survey, 290-303.

Stevenson, J.S. (1938): Lode-gold deposits of the Zeballos area, westcoast of Vancouver Island, British Columbia.

Stevenson, J.S. (1939): Geology and ore deposits of the Zeballos area,British Columbia. Transactions of the Canadian Institute ofMining and Metallurgy and of the Mining Society of Nova ScotiaVolume 42.

Stevenson, J. S . (1950): Geology and Mineral Deposits of the ZeballosMining Camp. British Columbia Department of Mines Bulletin27, 145 pages.

Toulmin, P., Barton, P.B and Wiggins, L.B. (1991): Commentary on thesphalerite geobarometer. American Mineralogist 76, no. 5-6(199106): 1038-1051.

Yorath, C.J., Sutherland Brown, A. and Massey, N.W.D. (1999):Lithoprobe, Southern Vancouver Island, British Columbia:Geology. Geological Survey of Canada Bulletin 498, 145 pages.

235 238

The Zeballos gold camp was discovered in the 1930s and closed in 1948 with intermittentartisanal mining continuing to present day. Almost 300 000 ounces of gold were mined from thecamp with the Privateer mine responsible for more that half of that production. This gold is hostedwithin quartz-carbonate-arsenide-sulphide veins that cut Bonanza volcanic rocks, Quatsinolimestone, the Zeballos Stock and associated adakitic dykes.

This study focuses on timing relationship between the late intrusive phases of the Zeballos stock,mafic dykes and gold mineralization at the Privateer Mine and lithological, geochemical andstructural controls on gold mineralization. This work entails U-Pb chronology of the intrusivephases, geochemistry, detailed mapping, petrography, alteration, mineralogy, fluid inclusions, stableisotope and structure of the gold-bearing quartz-carbonate veins.

The youngest rock unit cut by gold mineralized structures is an adakitic dyke associated with themain phase of the zeballos stock. U-Pb zircon geochronology of the adakitic dyke yields an age of35.413 ± 0.063 Ma.

Preliminary fluid inclusion studies are consistent with gold deposition from H O-CO -NaCl bearing

fluids with an approximate composition of X-H O equal to 0.974, an X-CO of 0.020 and X-NaCl

equal to 0.006 (2.0 wt. percent NaCl equivalent).Sphalerite in equilibrium with pyrite and pyrrhotite has been used to constrain pressures using thesphalerite geobarometer. Electron microprobe analyses of equilibrium sphalerite yields FeScompositions ranging from 16 to 18 mole percent. These correspond to pressures ranging from 2kilobars at low temperature to 3.5 kilobars at higher temperatures.

Combined pressure-temperature constraints based on the intersection of fluid inclusion isochoreswith the sphalerite goebarometric constraints suggests that vein formation occurred over a specificrange of pressures and temperatures from just over 300 °C at 1.5 kilobars to just under 500 °C at3.5 kilobars. Sulphur isotope studies indicates a disequilibrium between the main sulphide phaseswithin the veins.

The genesis of the Zeballos gold deposits are enigmatic with fluid inclusion studies and structuralinterpretations leaning towards a lower temperature shear hosted style of mineralization, while thetemperatures and pressures of vein formation, local proximity to shallow intrusives and goldfineness pointing towards an intrusion-related style of mineralization. Thus a genesis somewherebetween the two end member deposit types is likely.

2 2

2 2

Timing of Gold Mineralization at thePrivateer Mine, Zeballos Gold Camp,

Vancouver Island, BC: U-Pb and Ar-Ar evidenceDan Marshall , Natalka Podstawskyj , Magdalena Lesiczka and Adolf Aichmeier

1 2

1

2

Earth Sciences Department, Simon Fraser University, Burnaby, BC, V5A 1S6Privateer Mine, Zeballos BC, V0P 2A0

1 1

Produced with support from theBC and Yukon Chamber of Mines, Rocks to Riches Program

Abstract

DRIFT AND VALLEY FILL

QUARTZ DIORITE

DIORITE AND VOLCANICS BRECCIATEDBY QUARTZ DIORITE

GRANODIORITE

DIORITE CUT BY MANY GRANODIORITE DIKES

HORNBLENDE DIORITE

GABBRO

GEOLOGICAL CONTACTS

MOTOR ROAD

TRACTOR ROAD

PACK-HORSE TRAIL

FOOT TRAIL

(DEFINED, INFERRED)

ANDESITE, CHIEFLY PYROCLASTICS (DARK GREEN, HORNBLENDEFELDSPAR CRYSTAL TUFFS AND VOLCANIC BRECCIA), SOME LAVA

CALCSILICATE ROCKS

LIGHT-COLOURED VOLCANICS (FELDSPAR CRYSTAL TUFFS ANDDACITE TUFFS AND FLOWS)

LIMESTONE

ANDESITE CHIEFLY DARK GREEN LAVA (FINE-GRAINEDAND AMYGDALOIDAL PHASES)

VEIN

REPLACEMENT BODY

??

?

?

?

CABLE CROSSING

BRIDGE

PROSPECT

QUATERNARY

EOCENE

JURASSIC TRASSIC

MOUNT WASHINGTON INTRUSIONS

BONANZA GROUP

ISLAND INTRUSIONS

QUATSINO FORMATION

KARMUTSEN FORMATION

55

41

00

0m

654000m

GO

LDEN

GATE

CR

HIDDEN VALLEY

NO

MA

SH

RIIV

ER

MONCTON CR

GO

LD

VA

LLE

Y

CR

EEK

PRIVATEER CRSP

UD

CREEK

BIB

B

CR

RI V

ER

PANDO

R

A

CR

CR

BLA

CK

SAN

D

LIME

CR

CO

NTA

CT

CR

FAULT CR

CR

CU

RL

CR

MT

ZE

BA

LLO

S

VANIS

LE

CR

FALLS CR

ZE

B

ALL O

S

CR

MAQUINNA

CR

65-70°

60°

60°

50°

65°

75-80°

78-80° 80°

80°

85°

80°80°

85°

85°

75-80°

85°

85°

85°

86°65-90°

80°

50°

75°

63°

80°70-80°

80°65°

65°68°

55°

75-80°80-85°

80°

75-85°

70-80°

67-75°

80°

75-80°

SCALE FEET1000 1000 20000

LUCKYSTRIKE

BARNACLE

PEERLESS

CORDOVA

PANDORAPANDORA

OMEGA

MAQUINA

BODEN

VANISLE

PRIVATEER

PRIDENT

WHITESTAR

ZEBALLOSPACIFIC

SPUDVALLEY

MO

UNTZEBALLO

S

PROSPERITY

BRITANNIA M.

BIG STAR

RIMY

MT LUKWA

HOMEWARDMONITOR

CENTRALZEBALLOS

BRITANNIA

GOLDSPRING

KINGMIDAS

GOLDEN PORTAL

ANSWER

TAGORE

BEANOSUGAR LOAF MTN.

N

250 100

90 80 70

VOLCANISMVOLCANISM

SEDIMENTATIONSEDIMENTATION

PLUTONISMPLUTONISM

REGIONAL FABRICS& DEFORMATIONREGIONAL FABRICS& DEFORMATION

TIMING EVIDENCETIMING EVIDENCE

Time (Ma)Time (Ma)

60 50

50 0

40 30 20 10 0

CowichanCowichan Fold & thrustFold & thrustD2D2

S ??2S ??2

D1D1

S ??1S ??1S ??3S ??3 F low-angle3F low-angle3

F low-angle could bepre (Massey) or

post (Muller)Catface Intrusons

3F low-angle could bepre (Massey) or

post (Muller)Catface Intrusons

3

D4D4

DetritusDetritus

Well FoliatedKarmutsen &Bonanza

Well FoliatedKarmutsen &Bonanza

Mineralized Faultsand foliation in CatfaceMineralized Faultsand foliation in Catface

200

250 240 230 220 210 200 100

Karmutsen VolcanicsKarmutsen Volcanics

Sicker GroupVolcanics380 Ma

Sicker GroupVolcanics380 Ma

BonanzaVolcanics190-180 Ma

BonanzaVolcanics190-180 Ma

ClayoquotIntrusivesClayoquotIntrusives

IslandIntrusives

190-180 Ma

IslandIntrusives

190-180 Ma

Basal UnitBasal Unit

ComoxSilt & SstComox

Silt & SstParson Bay FmParson Bay Fm

Quatsino FmQuatsino Fm

Nanaimo GroupNanaimo Group

Carmanah GroupCarmanah Group??

GoldGold

ZeballosZeballos

MountWashingtonIntrusives

MountWashingtonIntrusives

TertiaryVolcanics

(Catface eq)

TertiaryVolcanics

(Catface eq)

METAMORPHISMMETAMORPHISM

MINERALIZATIONMINERALIZATION

Fe, Cu-AuFe, Cu-Au

SkarnSkarn

QQPermianPermian TriassicTriassic CretaceousCretaceous PaleogenePaleogene NeogeneNeogene

? VMS type ?? VMS type ?Cu porphyry ?Cu porphyry ?

HornfelsHornfelsMigmatiteMigmatite

Amphibolite ?Amphibolite ?

SurfaceSurface GreenschistGreenschist

? ?

SuiteSuiteCatfaceCatface

}

Jur.Jur.

Buttle Lk FmButtle Lk Fm

260270

D3D3

115±5 MaK-Ar Hb ?115±5 MaK-Ar Hb ?

UnconformityUnconformity

264±7MaU-Pb (Muller)

264±7MaU-Pb (Muller)

0.2 mm0.2 mm

50 m�50 m�50 m�50 m�

V

L

Qtz

Qtz

Qtz

Cal

25 m�25 m�

L V

100 300 500 7000

5

10

P(k

bar)

Temperature °C

Kyan

Sill

And

Sphalerite barometry

Maximum fluid inclusion isochore

Minimum fluid inclusion isochore

P-T conditions of vein formation

25 m�25 m�

Po

Sph

Py

Py

100 300 500 70010

5

0

P(k

ba

r)

Temperature °C

4

6

8

12

10m

ol%FeS

insphalerite

14

16

KyanSill

And

18

20 mol% FeS in sphalerite

Fig. 2. Schematic diagram illustrating thetiming of principal geological events in theNootka Sound region.

Ag

Au

AuZeballos Au (~23%Ag)

Fig. 10. Photograph showing the back of 2-3A vein (PrivateerMine). Some deformation is accommodated in a brittle manneras evidenced by the splays coming off the main vein. Whilesome structures within the vein show ductile deformationtextures (see arrow). Hammer (with flagging tape) for scale.

Fig. 8. Slab of gold bearing quartz (qtz) vein from the PrivateerMine. Slab length is approximately 15 cm. Note the relationshipbetween the galena (gn) which replaces arsenopyrite (apy) andgold (au) which cuts both the arsenopyrite and galena.

Fig . 11. Photomicrograph of euhedral quartz (Qtz) andcalcite (Cal) from the gold-bearing quartz-carbonate veinsfrom the Privateer Mine. The inset photomicrographsshow typical examples of the CO -bearing fluid inclusions

(right) and aqueous fluid inclusions (left). Both FIAs aretwo-phase inclusions consisting of and aqueous salineliquid (L) and vapour (V). Photos taken in plane polarizedtransmitted light.

2

Fig. 12. Photomicrograph of intergrown sulphides fromthe Privateer Mine showing textural equilibrium betweenpyrite (Py), pyrrhotite (Po) and sphalerite (Sph).Photograph taken in plane polarized reflected light.

Fig. 13. Sphalerite geobarometry diagram showing theisocompositional contours for mole % FeS for sphaleritein equilibrium with pyrite and pyrrhotite (Toulmin, 1991).The position of the aluminosilicate triple point is shown forreference in a dashed pattern. The range of compositionsreported from electron microprobe analyses are shown ingrey with the lower temperature constraint defined by fluidinclusion total homogenization temperatures and theupper temperature constraint based on stable mineralassemblage within the veins. And: Andalusite, Kyan:Kyanite, Sill: Sillimanite.

Fig. 14. Pressure temperature diagram showing the rangeof conditions for quartz-carbonate veins formation (darkgrey) from the combined constraints of sphaleritegeobarometry and the fluid inclusion isochores.

Granodiorite (Adakitic) Dyke

Mafic Dyke Skarn

Fig. 3. Two dyke (mafic and felsic)intersection in skarn host rock in 2-3A VeinDrift; Privateer Mine. Both dykes are cut bystructures associated with Au mineralization.

Fig. 1. Geologic map of the Zeballos region (modified fromStevenson, 1950)

1

10

100

1,000Zeballos Region Adakitic Rocks

La Ce P

rNd

Sm E

uGd Tb D

yHo E

rTm Y

b Lu

Spud Creek adakitic dike

Gold Valley adakitic dike

Privateer mine 2-3A adakitic dike

Fig. 7. Rare Earth Element (REE) plot of the adakitic rocks fromthe Zeballos area, including the adakitic dyke cut by the 2-3Avein gold mineralization at the Privateer Mine. The REE patternof the 2-3A adakitic dyke is consistent with garnet-restiteequilibration with some possible sediment assimilation.

Fig. 5. U-Pb Concordia diagram forthe granodiorite dyke shown in Fig.3. The zircon yields a concordantage of 35.41 ± 0.06 Ma.

Fig. 4. Ar-Ar diagram for the mafic dyke,shon in Figure 3. The sample yields an ageof 37.0 ± 1.2 Ma.

Fig. 6. Unabraded zircons takenfrom the granodiorite dyke alongthe 2-3A vein drift, Privateer Mine,Zeballos, BC.

Fig. 9. Au-EDS spectrum for Privateer Mine sample. This isconsistent with the gold containing 23 weight percent silver.This relatively high silver content is generally thought torepresent gold precipitation in the epithermal environment. Thusthe Privateer Mine may have a component of epithermalmineralization in its genesis.

40

38

36

34

32

30

0.0046

0.0050

0.0054

0.0058

0.0062

0.029 0.031 0.033 0.035 0.037 0.039 0.041

207Pb/

235U

20

6P

b/2

38U

Concordia Age = 35.413 ±0.063 Ma

(2 , decay-const. errs ignored)

MSWD (of concordance) = 0.13,

Probability (of concordance) = 0.72

�

Corrected for mass discrimination, common Pb (assumed to be all blank) and spike

1 BP5001 1 Ab zr, lpr 0.005 246 0.38 6.9 1.6 298.43 28.45 0.00553 0.00002 0.0348 0.0018 0.0457 0.0023 35.40 0.12 34.8 1.70 -- -- --2 BP5002 1 Ab zr, lpr 0.005 107 0.38 3.0 1.9 118.92 20.38 0.00552 0.00004 0.0359 0.0048 0.0472 0.0064 35.40 0.28 35.8 4.70 67.0 150.60 41.31 BP5003 1 Ab zr, spr 0.003 179 0.40 4.9 1.2 280.0 27.75 0.00550 0.00002 0.0350 0.0020 0.0462 0.0026 35.20 0.14 35.0 1.92 16.8 58.60 -250.22 BP5004 1 Ab zr, spr 0.003 308 0.37 8.5 0.9 638.9 44.72 0.00550 0.00001 0.0355 0.0008 0.0468 0.0010 35.30 0.10 35.4 0.79 43.8 53.80 4.8

zr - zircon grain; Ab - abraded; lpr - long prismatic; spr - short prismaticPbrad is total Pb radiogenic PbPbcom is total measured common Pb assuming the isotopic composition of laboratory blank:206/204 - 18.221; 207/204 - 15.612; 208/204 - 39.360 (errors of 2%).Th/U calculated from radiogenic 208Pb/206Pb ratio and 207Pb/206Pb age assuming concordance.Disc - per cent discordance for the given 207Pb/206Pb ageUranium decay constants are from Jaffey et al. (1971).

No. Anal. Description Wt. U Th/U Pbrad Pbcom 2 sig 2 sig 2 sig 2 sig 2 sig 2 sig Disc.(mg) (ppm) (pg) (pg) 204Pb 204Pb 238U 235U 206Pb 238U 235U 206Pb (%)

NP04-10-13 Zeballos

FOOTNOTES TO TABLE

206Pb 207Pb 206Pb 207Pb 207Pb 206Pb 207Pb 207Pb

qtz

au

apy

gn

80

60

40

20

0

0 20 40 60 80 100

Cumulative Ar Percent39

Ag

e(M

a)

Box height 2�Plateau steps are filled, rejected steps are open:

NP04-10-07 Whole rock

Plateau age = 37.0 1.2 Ma

(2 , including J-error of 0 .5%)

MSWD = 0.73, probability = 0.62

Includes 87% of the39

Ar

+

�

RO CKS TO R I CH E S

Ministry of Energy and MinesMines and Minerals Division

Geofile 2005-21