Epithermal Gold Deposits

EPITHERMAL GOLD DEPOSITS BRUCE E. TAYLOR Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8 Corresponding author’s email: [email protected] Abstract Epithermal Au (±Ag) deposits form in the near-surface environment, from hydrothermal systems typically within 1.5 km of the Earth’s surface. They are commonly found associated with centres of magmatism and volcanism, but form also in shallow marine settings. Hot-spring deposits and both liquid- and vapour-dominated geothermal systems are commonly associated with epithermal deposits. Epithermal Au deposits are commonly consider to comprise one of three subtypes: high sulphidation, intermediate sulphidation, and low sulphidation, each denoted by characteristic alteration mineral assemblages, occurrences, textures, and, in some cases, characteristic suites of associated geochemical elements (e.g. Hg, Sb, As, and Tl). Base metal (Cu, Pb, and Zn) and sulphide minerals may also occur in addition to pyrite and native Au or electrum. In some epithermal deposits, notably those of the intermediate-sulphidation subtype, base metal sulphides may comprise a significant ore constituent. Canadian Au production from epithermal deposits has been minor (