A regional SPECTREM EM survey of the Palaeo-Proterozoic Bryah Basin, Western Australia - Providing insights into a geological setting highly prospective for VMS Cu-Au Mineralisation.

Summary The Bryah Basin, part of the Capricorn Orogen, in northern Western Australia contains a succession of mafic and ultramafics overlain by clastic and chemical sedimentary rocks. The Basin is host to significant mineralisation, including the DeGrussa and Horseshoe Cu-Au VMS deposits. Among the challenges in the study of, and exploration for, these mineral systems is the paucity of outcrop and the extent and variability of a complex regolith cover. To better understand this regolith, a reconnaissance, regional-scale, SPECTREM AEM survey over the Bryah Basin in 2012. The data were inverted using a smooth model layered earth inversion, with the GA-LEI algorithm. In this paper we compare results on mapping regolith variability obtained from the full inversion of the SPECTREM data against a regolith structure obtained from the fast approximate transform of the same data set. For the Bryah Basin the inverted SPECTREM data show the most dominant regolith features are associated with sediment filled palaeovalleys. Their orientation indicates a strong lithostructural control. The regional regolith framework defined from this study provides a basis for better understanding and interpreting an extensive regolith geochemical data set, particularly with respect to the identification of metalloid anomalies linked to buried Cu-Au mineral systems.