Multiple origins of Canadian Cordilleran gold deposits: geochemical characteristics
Two types of lode Au mineralization (Mother Lode and Epithermal) can be recognized in the Canadian Cordillera by geochemical characteristics. The Coquihalla Au belt, a typical ML district, has steeply-dipping Q-cc-ab-Au veins. Host rocks are greywackes, slates and greenstones in fault contact with a serpentinite body. Isotopic analyses: Q-cc and antigorite-mt paris gives temperatures around 250/sup 0/C. delta/sup 18/O/sub SMOW/ are exceptionally high: vein Q = 16 to 18 per thousand, antigorite = 7.4 to 9.5 per thousand, and cc = 14 to 18 per thousand with delta/sup 13/C/sub PDB/ =-2.9 to -6.9 per thousand. deltaD are low: -111 to -142 for the serpentines and -84 to -100 for fluid inclusion waters extracted by crushing vein Q. These fluids have low salinity and contain CO/sub 2/. The delta/sup 18/O for the ore fluid is about 8 per thousand and was also the serpentinizing fluid. The deltaD suggest that the fluid was dominantly meteoric, but evolved by reaction with the metasediments during deep circulation. The typical ML assemblage is Q-cc-ab with aspy, py, po, Au, +/-AU tellurides +/- scheelite; Au/Ag = 4 to 7 in this belt. Other ML deposits in BC show similar isotopic and mineralogic traits. Epithermal deposits in the Canadian Cordillera are comparable to well-studied US examples: their fluids were shallow-circulated meteoric waters (delta/sup 18/O=-14 to -7), delta/sup 18/O=-5 to +2, T=200-300/sup 0/C, Au/Ag<1, and have Q, chalcedony, cc, hematite, adularia, barite, py, cpy, Ag/sub 2/S, Au, electrum and anomalous Hg, As, and Tl contents. The association of Hg and Sb occurrences near many B.C. ML deposits suggests that these may be the epithermal expression of deeper ML mineralization.
- Research Organization:
- Univ. of Alberta, Edmonton (Canada)
- OSTI ID:
- 6458726
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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ALBERTA
GOLD ORES
BRITISH COLUMBIA
GEOTHERMAL FLUIDS
ROCK-FLUID INTERACTIONS
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GEOCHEMISTRY
GEOLOGIC FAULTS
GEOLOGIC HISTORY
ISOTOPE RATIO
MINERALOGY
PETROGENESIS
PETROLOGY
QUANTITATIVE CHEMICAL ANALYSIS
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FLUIDS
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