Geodynamically indicated targeting strategy for shale-hosted massive sulfide Pb-Zn-Ag mineralisation in the Western Fold Belt, Mt Isa terrane

There is ongoing debate with respect to the genetic models for shale-hosted massive sulfide Pb-Zn-Ag deposits contained in the Palaeoproterozoic to Mesoproterozoic intracontinental Isa Superbasin in the Western Fold Belt, Mt Isa terrane. Favourable sites of mineralisation can be predicted based on understanding the tectonic setting of the Isa Superbasin, the structural controls of mineralisation and the chemically favourable environments for ore deposition. Shale-hosted massive sulfide Pb-Zn-Ag deposits are hosted in successions deposited during the dominant sag-phase of the Isa Superbasin. These deposits are localised at the Intersections of major basin-scale extensional faults and are hosted in both shallow-marine and deeper water carbonaceous shales that are characteristically anoxic and located near or at maximum flooding surfaces. All major shale-hosted massive sulfide Pb-Zn-Ag deposits are located to the west of the Mt Isa Rift (ca 1710-1670 Ma). This spatial association is explained by an asymmetrical lithosphere extension model for the evolution of the Isa Superbasin. Elevated geothermal gradients at the location of maximum subcrustal lithospheric thinning to the west of the Mt Isa Rift may have driven the migration of basinal brines. Increased subsidence at this location produced favourable anoxic sedimentary horizons for metal precipitation during orebody formation.