Seismic exploration for volcanogenic massive sulphides: The DeGrussa copper-gold mine, Western Australia

Abstract

Traditional geophysical prospecting techniques used for mineral exploration rarely provide either the depth of penetration or resolution required to accurately target orebodies at depth. Based on this, the seismic reflection method was trialled over a known VMS orebody at the DeGrussa copper-gold mine, Western Australia, in the hope of providing a viable exploration tool for deeper depths of investigation. However, a structurally complex geologic setting and a thick, highly variable regolith caused significant challenges in the processing of the seismic data. An initial 3D survey was not successful in imaging the orebody, so a follow-up downhole and 2D survey was acquired to address the potential issues. After verifying the in-situ seismic properties of the orebody through zero-offset Vertical Seismic Profiling (VSP) and increasing the down-dip offset range in the follow-up 2D survey it was found that the target provided a clear and unambiguous seismic response. However, a deep and variable regolith continued to cause significant issues during the imaging phase. This was overcome by applying a tomography-derived velocity field to a Kirchhoff migration, which produced outstanding results. Numerous tests and extensive data analyses eventually verified the seismic technique as a viable exploration tool for the region, with the direct detection of the target orebody.