The influence of basin architecture on Au fertility - evidence from the Capricorn Orogen

摘要

Opening up greenfields regions for minerals exploration programs is best facilitated through understanding a regions mineral prospectivity, and the opportunity that exists to find a new deposit. The Capricorn Orogen is a greenfields-dominated region, with known mineral occurrences or deposits formed during the Paleoproterozoic to Neoproterozoic. Mineralisation in this region can be related to basin development, inversion and orogenesis. Extension, on a regional scale dominates the tectonic processes observed in the region through time and is interspersed by abrupt periods of contractional orogenesis, manifested through the 2005-1950 Ma Glenburgh and 1830-1780 Ma Capricorn Orogenies. Prospectivity models generated for base metals and gold in the southern Capricorn Orogen suggest that there is a broad spatial link between these mineral systems, although they are separated by up to 200 million years of geologic history. The key link between base metals and gold mineralisation appears to be the deep crustal-scale architecture. The architecture developed initially with rifting of the Yilgarn Craton in the region to form the Yerrida Basin at about 2200 Ma and was reactivated during subsequent orogenesis. Reactivated deep crustal-scale faults that formed during early rifting are present throughout the region. However, the northern part of the Bryah Sub-basin of the Yerrida Basin appears the most prospective. In addition, Au mineralisation in this area occurred in an intraplate setting, unlike earlier formed Au in the Glenburgh Terrane to the west that occurred during accretion of the Glenburgh Terrane to the Yilgarn Craton. The mechanism for the focus of Capricorn-aged gold around the Yilgarn margin is unknown. However, it may be related to the focus of fluid and magma over a zone of weakness caused by the earlier rifting event.