Costerfield antimony-gold deposit, southeast Australia: Coupling between brittle deformation and dissolution-precipitation reactions in the Melbourne Zone

摘要: Abstract The antimony-gold deposits at Costerfield are a swarm of ‘dyke-like’ lodes within brittle transpressional fault system. They hosted in the Lower Silurian sedimentary rocks Melbourne Zone Lachlan Orogen. Individual dominated by stibnite or stibnite-gold and widths vary from 1 cm to ∼200 cm (averaging 30 cm) lengths can exceed 1 km. Lodes occur as fault-parallel layers lenses mantled deformed quartz-rich margins overgrowths hydrothermal quartz carbonate. Inclusions stibnite-rich include vuggy randomly oriented prismatic crystals, crack-sealed stretched with sugary mosaics equant grains breccias. Randomly textures, common centre lodes, indicate free growth fluid. Throughout mineralized system, has replaced overgrown earlier quartz. Deformed lode preserve sub-horizontal lineations evidence oblique crack-seal re-opening that reflect emplacement associated late sinistral strike-slip movements bounding faults. Crystallographic orientation data collected marginal quartz, using neutron diffraction supported microstructural observations, reveal also involved dissolution-precipitation creep pressure solution. Both overprinted later microfractures, which there been precipitation stibnite, pyrite, arsenopyrite, sphalerite minor gold. 3 D tomography revealed individual gold voxel sizes ranging 140 µm ∼580 µm, were located arsenopyrite-gold domains overprint stibnite. mechanical evolution short-lived processes combination crystallization active zones. These ore bodies provide insights about dynamics fluid flow velocities when faults breach over-pressured reservoirs Our results suggest deposit was formed directly metal-rich metamorphic fluids produced during Tabberabberan (∼375 Ma) prograde metamorphism near base Paleozoic Zone, lie above Proterozoic Selwyn Block. From reinterpretation seismic reflection data, deformation wedge is characterized thrusts isolating relatively undeformed packages units, moved piggyback manner up west-dipping ore-bearing migrated upwards, least part, along these footwall Heathcote Fault Zone. In upper levels package, out-of-sequence strike-slip, sub-vertical splays second order carried mineralizing orebodies. East-west compression Orogeny preceded northwest-southeast-oriented stress field reflects collision VanDieland against Gondwanan margin. This faults, turn controlled overall permeability