Contrasting geochemistry of orogenic gold deposits in Yukon, Canada and Otago, New Zealand

摘要: The Yukon-Tanana Terrane (YTT) of western Yukon Territory in NW Canada and Otago Schist belt (OSB) South Island, New Zealand share similar geological evolutionary histories as convergent orogenic belts. Both belts host gold deposits mainly Jurassic to Early Cretaceous age. mineralization the YTT occurred during orogenesis stacking previously-metamorphosed (Palaeozoic) greenschist-amphibolite facies metasediments, metavolcanic rocks, metagranitoids. OSB latter stages terrane accretion un-metamorphosed turbidites with minor basaltic rocks. Metamorphism mobilised background levels Au (0.6–1.3 ppb), As (2–20 ppm), Sb (0.1–1 ppm), W ( c . 0.5–2 ppm; 500–10 000 ppm) transformed pyrrhotite on a regional scale. In contrast, rocks had generally low contents (1–2 ppm) apart from some As-rich quartzites (up 100 ppm As). Consequently, there was less available for mobilisation, have lower concentrations this pathfinder element compared OSB. especially metagranitoids, anomalous Mo (10–300 ppm), many contain elevated Mo, locally including molybdenite. (2–200 ppm), along As, diagenetic pyrite, but became largely dispersed through metamorphic pile grade increased pyrite pyrrhotite. only marginally 1 ppm), no molybdenite, accessory scheelite these is distinctly Mo-poor. Only mobilisation base metals belts, sparse metal sulphides. Orogenic differ that (and other associated elements) remobilised relatively local sources (e.g. pre-existing Cu-Mo-Au porphyry or volcanogenic sulphide mineralization) whereas larger volumes homogeneous rock at depth.