Role of geophysics in exploration for MVT lead-zinc deposits on the Lennard Shelf, Western Australia

Abstract

The exploration strategy in the search for Mississippi Valley-type (MVT) mineralisation on the Lennard Shelf has been modelled on the approach commonly used in exploration for similar mineralisation in North America. Regional areas of interest are defined using a combination of geology, geochemistry and geophysics, then systematically grid-drilled. Several MVT lead-zinc deposits have been discovered on the Lennard Shelf through the application of this strategy. Mississippi Valley-type lead-zinc deposits are difficult geophysical targets. Their geophysical characteristics have been studied on the Lennard Shelf to provide a guide for more cost-effective exploration both on the Lennard Shelf and elsewhere. On a regional scale, gravity and aeromagnetic surveys, used in conjunction with geochemistry, effectively focus exploration into favourable structural and lithological settings. Detailed gravity and seismic surveys delineate areas of the host carbonates in regions of shallow cover. Several known Mississippi Valley-type deposits and prospects on the Lennard Shelf are associated with extensive marcasite haloes and associated induced polarisation anomalies. In areas of shallow cover, the induced polarisation method can be used to cost effectively define prospective areas by mapping mineralised systems on a semi-regional scale. These areas can then be tested using grid drilling.