The characteristics, origins, and geodynamic settings of supergiant gold metallogenic provinces

There are six distinct classes of gold deposits, each represented by metall ogenic provinces, having 100's to > 1000 tonne gold production. The deposit classes are: (1) orogenic gold; (2) Carlin and Carlin-like gold deposits; (3) epithermal gold-silver deposits; (4) copper-gold porphyry deposits; (5) iron-oxide copper-gold deposits; and (6) gold-rich volcanic hosted massive sulfide (VMS) to sedimentary exhalative (SEDEX) deposits. This classificat ion is based on ore and alteration mineral assemblages; ore and alteration metal budgets; ore fluid pressure(s) and compositions; crustal depth or dep th ranges of formation; relationship to structures and/or magmatic intrusio ns at a variety of scales; and relationship to the P-T-t evolution of the h ost terrane, These classes reflect distinct geodynamic settings. Orogenic g old deposits are generated at mid-crustal (4-16 km) levels proximal to terr ane boundaries, in transpressional subduction-accretion complexes of Cordil leran style orogenic belts; other orogenic gold provinces form inboard by d elamination of mantle lithosphere, or plume impingement. Carlin and Carlin- like gold deposits develop at shallow crustal levels (< 4 km) in extensiona l convergent margin continental arcs or back arcs; some provinces may invol ve asthenosphere plume impingement on the base of the lithosphere. Epitherm al gold and copper-gold porphyry deposits are sited at shallow crustal leve ls in continental margin or intraoceanic arcs. Iron oxide copper-gold depos its form at mid to shallow crustal levels; they are associated with extensi onal intracratonic anorogenic magmatism. Proterozoic examples are sited at the transition from thick refractory Archean mantle lithosphere to thinner Proterozoic mantle lithosphere. Gold-rich VMS deposits are hydrothermal acc umulations on or near the seafloor in continental or intraoceanic back arcs . The compressional tectonics of orogenic gold deposits is generated by terra ne accretion; high heat flow stems from crustal thickening, delamination of overthickened mantle lithosphere inducing advection of hot asthenosphere, or asthenosphere plume impingement. Ore fluids advect at lithostatic pressu res. The extensional settings of Carlin, epithermal, and copper-gold porphy ry deposits result from slab rollback driven by negative buoyancy of the su bducting plate, and associated induced convection in asthenosphere below th e oyer-riding lithospheric plate. Extension thins the lithosphere, advectin g asthenosphere heat, promotes advection of mantle lithosphere and crustal magmas to shallow crustal levels, and enhances hydraulic conductivity. Siti ng of some copper-gold porphyry deposits is controlled by are parallel or o rthogonal structures that in turn reflect deflections or windows in the sla b. Ore fluids in Carlin and epithermal deposits were at near hydrostatic pr essures, with unconstrained magmatic fluid input, whereas ore fluids genera ting porphyry copper-gold deposits were initially magmatic and lithostatic, evolving to hydrostatic pressures. Fertilization of previously depleted su b-are mantle lithosphere by fluids or melts from the subducting plate, or i ncompatible element enriched asthenosphere plumes, is likely a factor in ge neration of these gold deposits. tron oxide copper-gold deposits involve pr ior fertilization of Archean mantle lithosphere by incompatible element enr iched asthenospheric plume liquids, and subsequent intracontinental anoroge nic magmatism driven by decompressional extension from far-field plate forc es. Halogen rich mantle lithosphere and crustal magmas likely are the causa tive intrusions for the deposits, with a deep crustal proximal to shallow c rustal distal association, Gold-rich VMS deposits develop in extensional ge odynamic settings, where thinned lithosphere extension drives high heat flo w and enhanced hydraulic conductivity, as for epithermal deposits. Ore flui ds induced hydrostatic convection of modified seawater, with unconstrained magmatic input. Some gold-rich VMS deposits with an epithermal metal budget may be submarine counterparts of terrestrial epithermal gold deposits. Rea l time analogs for all of these gold deposit classes are known in the geody namic settings described, excepting iron oxide copper-gold deposits.