Mineralogical and Geochemical Controls on the Formation of the Woods Point Dike Swarm, Victoria, Australia: Evidence from the Morning Star Dike and Implications for Sourcing of Au Within Orogenic Gold Systems

摘要: The Woods Point dike swarm of eastern Victoria, Australia, has produced over 133 tonnes (t) Au. Here, as in a number other orogenic Au provinces, close spatial relationship is observed between mineralization and intrusive rocks; this study focuses on the well-endowed Morning Star dike, gabbro to gabbro-diorite that ~28 t hydrothermal quartz-carbonate-pyrite vein-hosted further 24 placer gold derived from primary rocks area immediately around Star. fractionated magma formed dikes within was sourced staging chamber at depth 16 23 km; here, mantle-derived magmas were driven S saturation by assimilation crustal material, leading formation Cu-Ni-platinum group element (PGE)-Au–bearing sulfides, most which segregated settled toward bottom chamber. Emplacement initiated with tapping release chamber, forming swarm; flow differentiation bulges enabled segregation sulfide-bearing mafic units intermediate sulfide-barren these dikes. This exemplified primitive amphibole-rich, gabbroic sections more evolved portions dike. We suggest source well members Cu-PGE-Au sulfides left conduit system, for example Thomson River Copper Mine Mass balance calculations undertaken ~104 million (Mt) magmatic sulfide may exist system; if they are equivalent preserved probably contain 3% Ni 10% Cu. During postmagmatic metamorphism, we infer fluids flowed along dikes, interacting leaching some Au, subsequently deposited quartz-carbonate veins higher levels system.