Troubleshooting hydrogeochemical sampling in grassroots mineral exploration: a Case Study from central Australia's Western Amadeus basin

Early-stage exploration for ore deposits has historically included reconnaissance sampling of solid media. Sampling of natural waters for mineral exploration has been increasing since its initial adoption in the 1970s but has not yet become a standard greenfields exploration tool despite increased commercial availability of low detection limit water analyses. A practical field sampling methodology was developed by the CSIRO, and interpreting results appeared fairly straightforward after initial literature review. However, the practicalities of analyzing hydrogeochemical data from real-world mineral exploration samples has led to important learnings regarding the assessment of metal anomalism in natural waters. We present an example of highly base-metal anomalous samples from saline groundwaters in Australia. Several phases of water sampling across different seasons followed by pump testing of the anomalous water bore revealed that the extremely elevated copper anomalism was related to downhole equipment rather than a buried mineral system. We outline the evolution of field work and data interpretation that led to this conclusion as well as share guidelines for how to mitigate the effects of potential downhole contaminants to produce viable, geologically meaningful water sampling results for reconnaissance mineral exploration.