Application of deep-penetrating geophysical methods to mineral exploration: Examples from Western Australia

Abstract

The emergence of the concept of a “mineral system” has changed the way regional-scale mineral prospectivity is assessed. Geographically widespread data sets and deep-penetrating geophysical methods are required to map the various components of the mineral system, which may encompass areas of perhaps thousands of square kilometers and extend to mantle depths. Key mineral system components that can be detected in this fashion include deep-penetrating faults and the suture zones between major geologic blocks, which are important controls on the movement of metal-carrying magmas and brines in a variety of mineral systems. Two case studies from mineralized terrains in Western Australia illustrate the use of deep-penetrating geophysical methods in mineral exploration. Magnetotelluric (MT) data from a 300-km-long traverse in the Archean Yilgarn Craton map numerous steeply dipping conductive zones, which coincide with linear anomalies in potential field data and are interpreted as deep-penetrating faults. Also, lateral changes in crustal and upper mantle resistivity structure suggest the juxtaposition of two, or perhaps three, different major crustal blocks with intervening suture zones. Teleseismic data from a 250-km-long traverse in the Proterozoic Capricorn Orogen provide information on deep crustal structure and composition. Interpretation in association with deep seismic reflection data allows previously unrecognized suture zones to be recognized in the deep crust and under thick cover. Passive seismic and MT methods represent a comparatively cost effective way to identify key mineral system indicators of regional prospectivity, even in the geologically complex terrains of Western Australia.