Multiple origins of Canadian Cordilleran gold deposits: geologic-tectonic constraints

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6374587

Nesbitt, B E; Murowchick, J B; Muehlenbachs, K

Detailed examination of geologic and geochemical characteristics of lode gold deposits in the Canadian Cordillera indicates that there are at least two different, yet synchronous styles of gold mineralization: Mother Lode and Epithermal. Epithermal type deposits are hosted by Late Jurassic to Tertiary intermediate to felsic volcanic units in accreted island arc terrains. They have many characteristics in common with the better known US epithermal deposits including potassic, silicic and low pH alteration zones, quartz-chalcedony-calcite-barite gangue and Au/Ag, < 1.0. Mother Lode vein systems are found in most terrains of the Canadian Cordillera and typically show a spatial correlation with major Early Cretaceous to Tertiary transcurrent or thrust faults, but no consistent correlation with felsic plutons. Host rocks for Mother Lode deposits include a wide variety of rock types with a nearly ubiquitous association with serpentinites. All of the units hosting ore have been metamorphosed to low to middle greenschist facies. Mother Lode deposits are accompanied by ankeritic, albitic, sericitic and silicic alteration, have a characteristic gangue assemblage of, Qz, Carb, Alb, Mariposite +/- Scheelite, Asp, Py, Po, Cp and a Au/Ag > 1. The deposits appear to have formed from deep circulation of meteoric water in major fracture zones, typically transcurrent faults. Subsequent upward movement and cooling of the fluids caused deposition of gold and associated gangue. Geologic and geochemical similarities of Mother Lode deposits to Archean gold deposits indicate that such an origin may well have been responsible for many Archean deposits, as well.

• Research Organization: Univ. of Alberta, Edmonton (Canada)
• OSTI ID: 6374587
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

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CANADA
CENOZOIC ERA
CHEMICAL COMPOSITION
CHEMISTRY
CRETACEOUS PERIOD
FLUIDS
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GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
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GEOTHERMAL SYSTEMS
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MESOZOIC ERA
METAMORPHISM
MINERALIZATION
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PETROGENESIS
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ROCK-FLUID INTERACTIONS
TECTONICS
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VOLCANISM