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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
+
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RO CKS TO R I CH E S
Ministry of Energy and MinesMines and Minerals Division
Geofile 2005-21
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