The Central Gawler Gold Province is poorly known and poorly explored, principally because of the extensive development of regolith. CRC LEME is collaborating with Geoscience Australia and the Minerals Resources Group in the South Australian Department of Primary Industry and Resources to reduce the risk attached to exploration through the regolith in this terrain. We have integrated the interpretation of geological, geophysical, and calcrete geochemical data at known prospects in order to develop a strategy for generating ranked drilling targets.
This ranking strategy carries the assumption that Au anomalies in calcrete formed in in-situ regolith materials are associated with Au mineralisation at depth. However, this assumption ignores the possibility that Au is moving laterally through the regolith in groundwater. It has been established that groundwater is mobilising significant quantities of Au in areas of the central Gawler Craton. Au may be precipitated within the regolith when the chemical or physical conditions governing mobilisation change. This process could generate "false" Au anomalies.
Our research suggests that regolith geochemistry (surface and sub-surface) should be interpreted against the groundwater chemistry and an understanding of groundwater flow paths. Whereas groundwater chemistry can only be established by assaying samples from drillholes, groundwater flow paths can be mapped using a combination of geology and geophysics. At prospect scale, these results can be used as vectors to primary mineralisation, thereby refining targeting strategies.
