Uncovering the Musgrave Province in South Australia using airborne EM

Abstract

Two airborne electromagnetic (AEM) surveys were undertaken in the Musgrave Province in South Australia in 2016 with the objective to increase knowledge about cover characteristics, thereby helping reduce exploration risks and to gain an understanding of the groundwater resource potential of the area. The Province is highly prospective for magmatic Ni-Cu-PGE and IOCG deposits, where a transported regolith imposes a significant challenge to exploration. Effective exploration through this region requires an understanding of that cover, its character and its spatial variability. This cover is also a source of groundwater that supports community and environment but our understanding of this resource is compromised by the limited information we have about it. Two different systems, TEMPEST and SkyTEM, were used for the survey, each covering around 8000 line km with a line spacing of 2 km. The line spacing was deliberately chosen to provide a spatially coherent picture of the subsurface conductivity structure, particularly the buried palaeovalleys known to be present in the region. The two datasets were processed and inverted and the results assessed against known information from drill holes. Both systems map the palaeovalley systems in the area well and provide information about the location and geometry of these. Furthermore the results indicate that it is possible to map variability within the cover using AEM, as well as structural controls on the orientation of the palaeovalleys. Airborne electromagnetic surveys used in logistically challenging areas can therefore be a useful mapping tool for areas with varied but unknown cover sequence thickness and thereby reducing exploration risks, as well as increasing the information content about groundwater resources.