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

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. The deposits appear to have formed from deep circulation of meteoric water in major fracture zones,more » 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.« less