Geology

doi: 10.1130/0091-7613(1986)14<506:DOOLGD>2.0.CO;2 1986;14;506-509Geology

 Bruce E. Nesbitt, James B. Murowchick and Karlis Muehlenbachs Dual origins of lode gold deposits in the Canadian Cordillera  

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Dual origins of lode gold deposits in the Canadian Cordillera

Bruce E. Nesbitt, James B. Murowchick, Karlis Muehlenbachs Department of Geology, University of Alberta, Edmontor, Alberta T6G 2E3, Canada

ABSTRACT From Late Jurassic to late Tertiary time, two geologically,

geochemically, and genetically distinct gold mineralization processes were active in the Canadian Cordillera. One group of deposits can be characterized as epithermal because of its association with intermediate to felsic volcanics, regional caldera structures, low pH alteration zones, low Au/Ag values, and quartz-chalcedony-barite-fluorite gangue. The second group of deposits is mesothermal in character and has strong similarities to Ihe Mother Lode deposits of California, being associated with transcurrent faults, intermediate pH alteration zones, and quartz ± carbonate, albite, mariposite, pyrite, arsenopyrite, scheelite gangue. Compared to epithermal deposits, mesothermal deposits have higher As, W, and Au/Ag values, higher CO2 content in fluid inclusions, and S I 8 0 values of ore-forming fluids of +3°/oo to +10°/oo vs. -14°/oo to -7°/oo for epithermal deposits.

Like the gold deposits in Nevada and Colorado, epithermal mineralization in the Canadian Cordillera formed from the shallow circulation of meteoric water in subaerial, intermediate to felsic volcanic complexes. In contrast, mesothermal gold deposits throughout the North American Cordillera are shown to be the product of deep circulation and evolution of meteoric water in structures associated with major, transcurrent fault zones. Similarities between Archean lode gold deposits and mesothermal deposits of the Cordillera suggest that Archean lode deposits may have been produced by processes similar to those involved in the formation of Cordilleran mesothermal deposits.

INTRODUCTION An examination of the geology and geochemistry of lode gold de-

posits of the Canadian Cordillera indicates that at least two styles of gold mineralization, epithermal and mesothermal, are present. Both styles of mineralization occur in the various allochthonous terranes of the Cana-dian Cordillera and formed over a time span of Jurassic to Tertiary. Consequently, the Canadian Cordillera offers the opportunity to examine two different gold mineralizing systems that overlap in time and space.

On the basis of stable isotope analyses, as well as geologic and geo-chemical characteristics of the deposits, it is possible to discern several previously unrecognized aspects of the formation of gold lode deposits. First, mesothermal, lode gold deposits of the North American Cordillera appear to have been deposited from meteoric water that underwent ex-treme 1 8 0 enrichment and minor D enrichment. Second, such deposits appear to be one of the first deposit types to be recognized as having formed from such highly evolved meteoric waters in which the salinities are less than that of sea water. Third, geologic and geochemical similari-ties between Cordilleran mesothermal deposits and Archean lode gold deposits indicate that evolved meteoric fluids were possibly a major component of fluids involved in the formation of Archean lode gold deposits.

Most of the gold deposits examined in this study are hosted by ex-otic oceanic or island-arc terranes, which have been accreted onto the North American continent in various stages. In the Canadian Cordillera, the terranes with oceanic affinities (Fig. 1) are characterized by extensive chert, argillite, carbonate, basalt, and alpine-type ultramafics (Monger et al., 1982; Gabrielse, 1985). The terranes with island-arc affinities contain a range of mafic to felsic volcanic and volcaniclastic units interspersed

Legend Terranes

H H m Oceanic Cache Creek (CC) Eastern (EN) Bridge River (BR)

pillili Island Arc Alexandria (AX) Wrangellia (WR) Stikinia (ST) Quesnellia (QN)

Major Transcurrent Faults

Deposits

• Epithermal 1. Dusty Mac 2. Black Dome 3. Tocdoggone 4. Skukum — Wheaton River

A Mesothermal Coquihaila Bralorne — Pioneer Cariboo Polaris — Taku Juneau

10. Cassiar 500 km

Figure 1. Location of gold lode mineralization in Canadian Cordillera relative to distribution of accreted terranes. References: map—Monger et al. (1982); Black Dome—Church (1982); Toodoggone—Schroeter (1982); Dusty It/lac—Church (1985); Skukum-Wheaton River Area— Morin (1981); Coquihaila—Ray (1983); Bralorne-Pioneer—Joubin (1948); Cassiair—Panteleyev and Diakow (1982); Cariboo— Sutherland-Brown (1957).

with shallow-w ater carbonates. The amalgamation of Terrane I (Eastern, Quesnellia, Cache Creek, Stikine, and Bridge River terranes) occurred by Late Triassic tc Early Jurassic time (Monger et al., 1982). Terrane I was accreted onto the North American continent during the Middle Jurassic, forming the Onineca Crystalline Belt along the suture. By Late Jurassic time, the Wrangellia and Alexander terranes were amalgamated into Ter-rane II and attached to North America during the Cretaceous (Monger et al., 1982). Beginning in the Early Cretaceous and continuing into the middle Tertiary, northwest-trending, dextral, transcurrent faults displaced large segments af the accreted terranes northward relative to the North American continent (Gabrielse, 1985).

DEPOSIT CHARACTERISTICS With the recent discovery of the Toodoggone deposits in central

British Columbia, significant effort has bsen expended on exploration for epithermal type deposits in the Canadian Cordillera. The best examples

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of epithermal mineralization in the Canadian Cordillera are the Toodog-gone, Black Dome, and Dusty Mac deposits in British Columbia, and the Skukum deposit, Yukon (Fig. 1). The epithermal nature of these deposits has been recognized and described (Schroeter, 1982; Morin, 1981); how-ever, the contrast of these deposits with mesothermal deposits in the Ca-nadian Cordillera has not been previously emphasized.

The typical host rocks for epithermal deposits in the Canadian Cor-dillera are unmetamorphosed, Tertiary, felsic to intermediate volcanics including subaerial flows, ash, and tuff. These are best exemplified by the Dusty Mac and Black Dome deposits. The principal exception is found in the Toodoggone district where epithermal mineralization in interme-diate volcanics is Early Jurassic (Diakow, 1985).

Regional structure in the vicinity of epithermal gold deposits in the Canadian Cordillera varies from well-developed caldera structures in the Wheaton River district to relatively isolated, felsic volcanic piles as in the Toodoggone, Dusty Mac, and Black Dome deposits. The ores occur as stockworks or vein-fillings in fault zones or phreatic breccias, commonly with high-grade mineralization over a restricted depth interval with well-defined tops and bottoms. Veins are predominantly composed of quartz with lesser amounts of chalcedony, calcite, and barite in vuggy comb structures or symmetrically banded crusts. Sulfide and ore minerals in-clude pyrite, chalcopyrite, galena, acanthite, native gold, electrum, and argentite. Au/Ag values are typically <1 and usually between 0.05 and 0.20.

Hydrothermal alteration assemblages are characterized by extensive silicification, advanced argillic, phyllic, and potassic alteration, and the deposition of hematite, pyrite, and opal. Fluid inclusion data on Dusty Mac (Z. Xiaomao, 1985, personal commun.) indicate temperatures of homogenization of 200 to 300 °C with salinities typically 2 wt% NaCl equivalent or less and low CO2 content.

Panteleyev (1985, personal commun.) and Schroeter (1982) have noted a close similarity between the deposits described above and the epithermal deposits of the western United States. In particular, the asso-ciation of the Canadian Cordilleran deposits with relatively young, in-

termediate to felsic volcanics, the prominence of argillic alteration, and characteristic temperatures and salinities of fluid inclusions, all bear a strong resemblance to the better known deposits of the United States.

Though not generally recognized as a discrete style of mineralization in the Canadian Cordillera, mesothermal gold deposits are more com-mon and economically significant than epithermal deposits. Most of the major, lode gold mining districts, including Bralorne-Pioneer, Polaris-Taku, Coquihalla, Cassiar, Cariboo, and Juneau, Alaska (Fig. 1), possess distinctive characteristics similar to those of the mesothermal deposits of the California Mother Lode district.

As summarized in Table 1, mesothermal deposits in the Canadian Cordillera occur in a variety of host rocks including mafic to felsic vol-canics and intrusions, serpentinites, and clastic and chemical sedimentary units. This diversity of host rocks indicates that host-rock petrology is not a controlling factor in the formation of such deposits. However, one uni-fying factor concerning the host units is that they have nearly always been exposed to some degree of greenschist-facies metamorphism. The age of the host units of these deposits is Carboniferous to Early Jurassic (Monger et al., 1982); however, the ores are typically younger, varying from Late Jurassic in the east (Panteleyev and Diakow, 1982) to Tertiary in the west (Ray, 1983).

Analysis of the regional structural setting of mesothermal deposits in the Canadian Cordillera reveals a common spatial link with postmeta-morphic, transcurrent faults, as in the Bralorne-Pioneer, Coquihalla, and Cariboo districts (Fig. 1) (Hodgson et al., 1982). The veins in most dis-tricts occur in subvertical, commonly reverse faults which are subsidiary to major structures that crosscut intensely deformed assemblages of plu-tonic, volcanic, and/or sedimentary units. In spite of the complexity of the local structural setting, some high-grade ore shoots persist over verti-cal extents of more than 1500 m (Joubin, 1948).

The veins are typically a few centimetres to a few metres thick and are composed predominantly of quartz with lesser amounts of carbonate, albite, mariposite, and scheelite in textures characterized as either massive or ribboned. In addition, replacement mineralization is present in some

TABLE 1. CHARACTERISTICS OF GOLD LODE DEPOSITS OF CANADIAN CORDILLERA

Epithermal Mesothermal

Age

Petrology of host uni ts

Structural set t ing

Ores: mineralogy

textures

Au/Ag

Hydrothermal a l te ra t ion

Fluid inclusion data

Stable isotope data*

Ter t ia ry ; Late Jurassic

Intermediate to f e l s i c volcanics, ash, t u f f s , rare ly f e l s i c plutons; unmetamorphosed

Regional: calderas, volcanic centers Deposit scale: fau l t s and phreatic breccias

Quartz, chalcedony, c a l c i t e , hematite, adular ia, ba r i te , py r i t e , chalcopyr i te, argent i te , electrum, acanthite

Stockwork, vein f i l l i n g s , comb structures, crusts

Less than 1; t y p i c a l l y 0.20 to 0.05 S i l i c i f i c a t i o n , advanced a r g i l l i c , potassic

p r o p y l i t i c , p y r i t i z a t i o n

T„ = 200 to 300°C Homog. Low s a l i n i t y ; Low C02 content

S 1 8 V z = " 5 t 0 6°Fld Incl Calculated values for ore f l u i d s : 6 °0 = -14 to -1%0 6D = -160%0(north)

Late Jurassic to Ter t ia ry Mafic to f e l s i c volcanics and plutons, serpent in i tes ,

limestones, c las t i c sedimentary un i t s ; low to upper greenschist facies

Regional: major, transcurrent f a u l t zones Deposit scale: ve r t i ca l normal or reverse fau l t s in

highly deformed zones Ouartz, Ca-Fe-Mg carbonate, a l b i t e , scheel i te , mariposi te,

py r i t e , py r rho t i t e , arsenopyrite, graphi te, galena, chalcopyr i te, sphaler i te , native Au, Au-Ag t e l l u r i t e s

Massive or ribboned veins 0.1 to 5 m width, ore shoots up to 100s m length and depth; replacement zones

1 to 10 Carbonatization, s i l i c i f i c a t i o n , s e n s i t i z a t i o n ,

development of p y r i t e , mariposi te, a l b i t e , c h l o r i t e , t a l c , graphite

THomog. = 2 0 0 t 0 3 5 0 ° C

Low s a l i n i t y ; intermediate to high C02 content

= -1 603S„(north) s l 8 ° se rp = + 7 %° t 0

180%o; 6 D n d I n c l = -S0%o to -160%„ 6 i e 0 q t z = +14 to +181

i Dserp = "1 1 0 ' ° ° t 0

Calculated values fo r ore f l u i d s : 6180 = +5%0 to +9%o; <5D = -80%„ to -100%o (south), -140%o to -160S!o (north)

aD and 6 l e 0 re la t i ve to SM0W.

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districts. Pyrite, pyrrhotite, arsenopyrite, chalcopyrite, galena, and sphal-erite account for 3% to 15% of the vein material. Gold is present either as native gold or Au-Ag-tellurides and typically occurs in fractures crosscut-ting early pyrite, arsenopyrite, and quartz. Au/Ag ratios vary between 1 and 10.

Hydrothermal alteration associated with mesothermal deposits in the Canadian Cordillera is dominated by extensive ankeritic or dolomitic carbonatization, along with albitization, sericitization, silicification, and the development of pyrite, mariposite, and graphite in the wall rocks. This alteration assemblage contrasts sharply with the low pH alteration associated with epithermal deposits and indicates more alkaline condi-tions during alteration associated with mesothermal deposits. Fluid inclu-sion data from samples from Coquihalla, Cassiar, and Cariboo indicate temperatures of homogenization between 250 and 350 °C. Salinities are typically less than 2 wt% NaCl equivalent, and CO2 content is often substantial.

As in the case of epithermal deposits, there is a strong resemblance between the mesothermal deposits of the Canadian Cordillera and their U.S. counterparts, such as the California Mother Lode district as de-scribed in Knopf (1929) and Bohlke and Kistler (1986). In particular, the association with major, postmetamorphic, transcurrent structures and the occurrence in a variety of host rocks indicate that the deposits of the Canadian Cordillera are only part of a major mineralizing system stretch-ing from California to northern Canada and Alaska.

STABLE ISOTOPE EVIDENCE FOR THE ORIGINS OF ORE-FORMING FLUIDS

Of particular interest is whether or not the two processes described above were genetically independent. The answers to such questions usu-ally involve the use of S 1 8 0 and SD values from samples of ore and gangue to interpret the origins of the mineralizing fluids; however, to date no (5180 or <5D data have been published for any gold deposit in the Canadian Cordillera. Presented here are the results of a preliminary sur-vey of S 1 8 0 and 6D values from several Canadian Cordilleran deposits and implications of the results to the origins of ore-forming fluids.

Stable isotope analyses of quartz separates from two epithermal de-posits, Skukum (10 samples) and Dusty Mac (6 samples), indicate a range in 6 1 8 0 for vein quartz of -5°/oo to +20/0o. These results, in con-junction with a temperature estimate of 250 °C from fluid inclusions, in-dicate a S I 8 0 range of -14°/oo to -7°/oo for the fluids involved in the formation of these deposits (Fig. 2). Comparison of these <5180 values with the meteoric water line, which is believed to be relatively un-changed since Early Cretaceous time (Taylor, 1979), indicates that epi-thermal deposits were formed from meteoric water that had undergone moderate enrichment in 1 8 0 (Fig. 2). Studies of epithermal deposits in the western United States also show the involvement of slightly 1 8 0-enriched, meteoric water (Taylor, 1979).

Stable isotope studies of deposits of the Mother Lode district of Cal-ifornia show that these deposits formed from fluids with <5lsO values of +8°/oo to +16%0 and <5D values o f -10%0 to -50°/00 (Fig. 2) (Bohlke and Kistler, 1986; Marshall and Taylor, 1980; Weir and Kerrick, 1984). The coincidence of the Mother Lode results and the values believed to be in-dicative of metamorphic fluids has prompted many authors to conclude that metamorphic dehydration was probably the principal source of the mineralizing fluids of the Mother Lode (Weir and Kerrick, 1984).

The isotopic signatures of the mineralizing fluids at two Canadian deposits, Cassiar and Coquihalla, were determined from analyses of ore-stage fluid inclusions, vein quartz, and serpentinites associated with the deposits; fractionation factors at 250 °C from Taylor (1979) were used. Mineralogic and isotopic characteristics of aniigorites at Coquihalla and the isotopic data of Wenner and Taylor (1974) for Cassiar serpentinites indicate that serpentinites in both locations were affected by the ore fluids.

The <5180 values for the ore fluids (calculated from 52 quartz and 16 serpentinite samples from Coquihalla and 9 quartz samples from Cas-siar) range from +8°/00 to +12°/oo, which is similar to the range of S 1 8 0 values for the Mother Lode fluids (Fig. 2). However, the 6D values, -90°/oo to -120°/oo for Coquihalla (7 aniigorites and 6 fluid inclusion ex-tractions) and --130°/oo to -160°/oo for Cassiar (6 fluid inclusion extrac-tions and Wenner and Taylor's [1974] serpentine values recalculated to 250 °C) are much lower than those of the California deposits, paralleling the trend of lower <5D with increasing latitude.

The change in 5D values with latitude for mesothermal deposits (Fig. 2) indicate that meteoric waters, not metamorphic fluids, are re-sponsible for the formation of mesothermal deposits of the North Ameri-can Cordillera. These meteoric waters were highly enriched in 1 8 0 and somewhat enriched in D relative to local meteoric waters, indicating that substantial water-rock interactions occurred. This is one of the first re-ports of the involvement of such highly evolved, low-salinity meteoric water in ore de)X>sition. It is apparent that meteoric fluids were responsi-ble for the formation of both epithermal and mesothermal deposits; how-ever, because of the substantially greater extent of water-rock interaction involved in the generation of mesothermal deposits, distinctly different <5i80 signatures were developed in both systems.

GENETIC MODELS FOR LODE GOLD MINERALIZATION IN THE CANADIAN CORDILLERA

Research in the United States has resulted in a model for the forma-tion of epithermal deposits involving shallow circulating, meteoric waters

- 2 0

-40

- 6 0

5 -80

5 CO

§ -100

-120

-140

-160

-180

- 2 0 0 ^

1 r Archean Lode Au Deposit

Waters

Mother Lode Waters

Primary' Metamorphic Magmatic Waters -! Waters'-

Cassiar District, Northern B.C.

-25 -20 -15 -10 -5

S 1 8 ° S M O W

0 10 15 20

Figure 2. Diagram indicating variations in calculated 6D and 61 sO values from samples from epithermal and mesothermal deposits of United States an d Canada. Patterned areas surrounded by solid lines indicate S 1 8 0 values from quartz specimens calculated at 250 °C and ¿>D values of extracted fluid-inclusion waters. Patterned areas delim-ited by dashed lines indicate calculated values for 6D and 61 sO from analyses of serpentinite, assuming a temperature of 250 °C. Cassiar serpentinite calculations are based on data from Wenner and Taylor (1974). Only S 1 8 0 data are available for samples from Dusty Mac; therefore, the location is given as only approximate with respect to 5D. See text for references for data on California Mother Lode and Ar-chean gold deposits.

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being heated by cooling volcanics or plutons, the upward movement of the waters in faults or phreatic breccias, and deposition of ore and gangue in response to cooling and boiling of those fluids (Buchanan, 1981). Given the striking similarities in both geology and geochemistry between U.S. and Canadian examples, it is probable that the origin of epithermal deposits in the Canadian Cordillera is similar to the general-ized model.

The genesis of mesothermal deposits in both Canada and the United States is less well understood. On the basis of the data of this and other studies, it is likely that mesothermal deposits are a product of deep circu-lation, possibly to depths of 6 to 8 km, of meteoric water in the vicinity of major fault zones. With deep circulation, the temperature of the meteoric water increases to the range of 250 to 350 °C, and extensive water-rock interaction occurs, increasing the l s O and the CO2 content of the fluid. The fluids cool as they rise up faults or related structures, and reactions occur that increase the pH of the system and cause formation of extensive carbonate or albite alteration and deposition of the ore and gangue. The principal process causing the pH increase is most likely the effervescence of CO2 (MacDonald and Ray, 1984). The exact process re-sponsible for the deposition of the gold is, as yet, uncertain. However, the process must be active over a large volume, given the substantial vertical and longitudinal continuity of many of the vein systems. At shallower depths, the vein systems are characterized by the deposition of stibnite, with quartz and carbonate and, at even shallower depths, cinnabar, quartz and carbonate.

IMPLICATIONS A N D CONCLUSIONS As noted by various authors (e.g., Hodgson et al., 1982; Colvine

et al., 1984), Cordilleran mesothermal deposits and Archean lode gold deposits have many similarities in geology and geochemistry. Fluids involved in the formation of the Archean gold deposits can be characterized as low chloride, high CO2, and as having <5180 values of +4°/00 to +10°/oo (Colvine et al., 1984; Kerrich, 1983). To date, these re-sults have been used to support a genetic model for Archean lode gold deposits involving precipitation from metamorphic fluids ascending through strike-slip faults or breaks (Colvine et al., 1984; Kerrich, 1983). However, given the similarities in geology and geochemistry, Archean lode gold deposits, like Cordilleran mesothermal deposits, may have developed from deep circulation of meteoric water along transcurrent faults in accreted, oceanic, and/or island-arc terranes. An advantage of this model for the origin of Archean lode gold deposits is that it can ac-count for the very large volumes of fluid involved in the ore-formation process, such as the 8 x 1012 kg of fluid required for the formation of the Hollinger-Mclntyre deposits, Timmins, Ontario (Colvine et al., 1984).

In summary, gold lode mineralization in the Canadian Cordillera was produced by two independent, concurrent, ore-forming systems. Both processes involved circulation of meteoric water. In the epithermal style of mineralization, the water underwent shallow circulation and minor isotopic evolution and formed near-surface, precious-metal miner-alization. Mesothermal deposits formed from deep circulation of meteoric water in major fault zones, resulting in extensive isotopic evolution and a unique chemistry of ore-forming fluid that produced veins of great verti-cal extent with intermediate pH alteration assemblages.

REFERENCES CITED Bohlke, J.K., and Kistler, R.W., 1986, Rb-Sr, K-Ar, and stable isotope evidence

for the ages and sources of fluid components of gold quartz veins in the northern Sierra Nevada foothills metamorphic belt, California: Economic Geology (in press).

Buchanan, L.J., 1981, Precious metal deposits associated with volcanic environ-ments in the southwest, in Dickinson, W.R., and Payne, W.D., eds., Rela-tions of tectonics to ore deposits in the southern Cordillera: Arizona Geological Society Digest, v. 14, p. 237-262.

Church, B.N., 1982, The Black Dome Mountain goUksilver prospect, in Geologi-cal fieldwork 1981: British Columbia Ministry of Energy, Mines and Petro-leum Resources Paper 1982-1, p. 106-108. 1985, Volcanology and structure of Tertiary outliers in south-central, British Columbia, in Tempelman-Kluit, D., ed., Field guides to geology and mineral deposits in the southern Canadian Cordillera: Geological Society of America, Cordilleran Section, p. 5-1-5-46.

Colvine, A.C., Andrews, A . J . , Cherry, M.E., Durocher, M.E., Fyon, A.J., Lavigne, M.J., Jr., Macdonald, A.J., Marmont, S., Poulsen, K.H., Springer, J.S., and Troop, D.G., 1984, An integrated model for the origin of Archean lode gold deposits: Ontario Geological Survey Open-File Report 5524, 98 p.

Diakow, L.J., 1985, Potassium-argon age determinations from biotite and horn-blende in Toodoggone volcanic rocks, in Geological fieldwork 1984: British Columbia Ministry of Energy, Mines and Petroleum Resources Paper 1985-1, p. 299-300.

Gabrielse, H., 1985, Major dextral transcurrent displacements along the Northern Rocky Mountain Trench and related lineaments in north-central British Columbia: Geological Society of America Bulletin, v. 96, p. 1-14.

Hodgson, C.J., Chapman, R.S.G., and MacGeehan, P.J., 1982, Application of ex-ploration criteria for gold deposits in the Superior Province of the Canadian Shield to gold exploration in the Cordillera, in Precious metals in the North-ern Cordillera: Vancouver, British Columbia, Association of Exploration Geochemists, p. 173-206.

Joubin, F.R., 1948, Bralorne and Pioneer Mines, in Structural geology of Cana-dian ore deposits: Montreal, Canadian Institute of Mining and Metallurgy Symposium, p. 168-176.

Kerrich, R., 1983, Geochemistry of gold deposits in the Abitibi Greenstone Belt: Canadian Institute of Mining and Metallurgy Special Volume 27, 75 p.

Knopf, A., 1929, The Mother Lode system of California: U.S. Geological Survey Professional Paper 157, 88 p.

MacDonald, A.J., and Ray, G.E., 1984, Fluids responsible for lode gold deposi-tion in the Cordillera and the Superior Province: Implications for a cost-effective exploration technique: Geological Association of Canada, Cordilleran Section Program with Abstracts, p. 20.

Marshall, B., and Taylor, B.E., 1980, Origin of hydrothermal fluids responsible for gold deposition, Alleghany district, Sierra County, California: Geological So-ciety of America Abstracts with Programs, v. 12, p. 118.

Monger, J.W.H., Price, R.A., and Tempelman-Kluit, D.J., 1982, Tectonic accre-tion and the origin of the two major metamorphic and plutonic welts in the Canadian Cordillera: Geology, v. 10, p. 70-75.

Morin, J.A., 1981, Element distribution in Yukon gold-silver deposits, in Yukon geology and exploration 1979-80: Yukon Territory, Department of Indian and Northern Affaire, p. 68-84.

Panteleyev, A., and Diakow, L.J., 1982, Cassiar gold deposits McDame map-area, in Geological fieldwork 1981: British Columbia Ministry of Energy, Mines and Petroleum Resources Paper 1982-1, p. 156-161.

Ray, G.E., 1983, Carolin Mine—Coquihalla Gold Belt Project, in Geological fieldwork 1982: British Columbia Ministry of Energy, Mines and Petroleum Resources Paper 1983-1, p. 63-84.

Schroeter, T.G., 1982, Toodoggone River, in Geological fieldwork 1981: British Columbia Ministry of Energy, Mines and Petroleum Resources Paper 1982-1, p. 122-133.

Sutherland-Brown, A., 1957, Geology of the Antler Creek area: British Columbia Department of Mines Bulletin 38, 104 p.

Taylor, H.P., Jr., 1979, Oxygen and hydrogen isotope relationships in hydrother-mal mineral deposits, in Barnes, H.L., ed., Geochemistry of hydrothermal ore deposits: New York, John Wiley & Sons, p. 236-277.

Weir, R.H., Jr., and Kerrick, D.M., 1984, Mineralogic and stable isotopic rela-tionships in gold-quartz veins in the southern Mother Lode, California: Geo-logical Society of America Abstracts with Programs, v. 16, p. 688.

Wenner, D.B., and Taylor, H.P., Jr., 1974, D/H and 1 8 0 / 1 6 0 studies of serpen-tinization of ultramafic rocks: Geochimica et Cosmochimica Acta, v. 38, p. 1225-1286.

ACKNOWLEDGMENTS Supported by NSERC Strategic Grant G1107. We thank G. Ray, A.

Panteleyev, D. Tempelman-Kluit, Z. Xiaomao, and L. Walton for supplying some of the samples used in the study and for their helpful discussions. Technical assistance was provided by E. Toth and P. Maheux.

Manuscript received August 23, 1985 Revised manuscript received February 19, 1986 Manuscript accepted March 12, 1986

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