Architecture and evolution of the West Musgrave Province, and implications for mineral prospectivity

Abstract

The West Musgrave Province preserves a geological history spanning much of the Proterozoic, including two major Grenville-aged orogenic events, ca. 1345-1120 Ma. These were followed by the intraplate Giles Event, ca. 1080-1050 Ma, which is characterised by 1- the voluminous mafic intrusions of the Giles Complex and 2- the deposition of a thick sequence of bimodal volcanic rocks and sedimentary rocks (the Bentley Supergroup). The architecture resulting from these events was subsequently overprinted by later events, the ca. 600-520 Ma Petermann Orogeny, and the ca. 450-350 Ma Alice Springs Orogeny. Here we use aeromagnetic, gravity and magnetotelluric data, constrained by geological mapping and petrophysical data, to characterise the 3D architecture of the region, and to unscramble its structural evolution. Early deformation events are well preserved in places, although they do not permit a robust interpretation of the regional architecture at that time. The architecture of the Giles Event is extremely well preserved, and a complex polyphase history is conserved. A series of discrete to semi-continuous deformation events is recorded, with a dominant ESE-WNW trend supplemented by additional NE-SW and N-S trends, each of which was active at several times during the event. Later events are manifested primarily as reactivations of earlier structures. Using this architectural framework along with a variety of other spatial datasets (geology, geochemistry etc) GIS-based prospectivity analysis was applied using a mineral systems approach, targeting Ni, Cu, PGEs and orogenic gold. The conceptual method used compares spatial distributions of various targeting criteria, represented by predictor maps. Each predictor map is then related to metal source, fluid pathways, and chemical and physical trap zones. The output prospectivity maps are used as decision-support tools for exploration and reinforce the idea that the area is highly prospective for magmatic nickel-copper and PGE?s deposits.