This address was presented at the annual Prospectors and Developers Association of Canada International Convention, Trade Show and Investors Exchange (PDAC), 4-6 March 2005 in Toronto, Canada.
Geoscience Australia's use of deep crustal seismic reflection imaging techniques to determine the crustal architecture near several world-class mineral deposits (Kalgoorlie, Broken Hill, Mount Isa, McArthur River, Olympic Dam) is challenging current understanding of Australia's geology, ore deposit models and prospectivity. The focus has been identifying the main crustal-scale fluid migration pathways and depositional environment (traps). Seismic reflection images suggest that the crust of the Eastern Goldfields (Yilgarn Craton) formed in an accretionary orogen with gold associated with higher-order splays along corridors linked to crustal-penetrating faults.
The Broken Hill survey showed the major structures dip SE (not NW) leading to a new 3D geological model for the supergiant Ag-Pb-Zn Broken Hill deposit. The Mt Isa seismic survey suggests that mineralised fluid circulation in the Western Succession was controlled by the Adelheid Fault not the Mt Isa Fault, and revealed Cu-Au deposits associated with the previously unmapped Marimo Fault in the Eastern Succession. The super giant Olympic Dam deposit (3810 Mt @ 1.1% Cu, 0.4 kg/t U308, 0.5 g/t Au) is associated with mantle-penetrating structures at a major crustal boundary. The giant McArthur River Ag-Pb-Zn deposit lies at the edge of a foreland fold-and-thrust belt rather than a rift setting. The newly-defined crustal architecture for many of these deposits requires a re-examination of current geological and ore deposit models. We discuss the exploration implications of these new results and the use of seismic to image alteration haloes around ore bodies.
