Regional scale hydrogeochemical mapping of the northern Yilgarn Craton, Western Australia: a new technology for exploration in arid Australia

The northern Yilgarn Craton, with an extensive mineral exploration history and relatively fresh and neutral groundwaters, was selected to test the utility of regional hydrogeochemical mapping in Australia. The assembled data of 2509 groundwater samples (generally at 4–8 km spacing) are relatively unbiased, allowing robust statistical analysis such as testing sample types (flowing v. ‘stagnant’), contamination, and lithological controls on groundwater characteristics. Lithological indicators were developed to map underlying bedrock through cover. Areas with discrepancies between groundwater results and previous geological mapping were identified. Where these are areas previously discounted as prospective for mineral commodities, they may now be re-considered on this basis. Even in well explored parts of this region, this study identified new areas which may have prospective rocks overlain with a thin (<50 m) veneer of granitic material. A large background data set was produced that has significant benefits for lithological discrimination, mineral exploration, guiding human and livestock drinking water supplies and environmental management (e.g. mine closure). Groundwater chemistry can effectively map large-scale lithological changes in these semi-arid environments, and in turn can reduce uncertainly about the prospectivity of areas within the northern Yilgarn Craton. This should reduce the drilling and associated costs required to delineate a target. The methods and interpretation developed in this study will enhance mineral exploration into covered environments as much of the northern two thirds of Australia has similar groundwater environments. This methodology can be expanded into covered arid terrains worldwide. Additionally, this can be used as background to improve interpretation of other small scale studies. Improving the exploration potential of other more difficult regions of Australia will encourage industry exploration in Australia, and provide potential future economic gains.