Hydrogeochemistry has grown in popularity as a non-invasive technique to quickly assess a region and narrow the focus for more targeted mineral exploration. We present a new approach for applying hydrogeochemistry for more sensitive anomaly detection, using hydrogeochemistry collected in the wider Broken Hill region.
The Broken Hill region is extremely well-endowed with mineral systems, including the world-class Broken Hill Line of Lode (Pb-Zn-Ag). Previous work from Geoscience Australia and CRC LEME has already demonstrated the capability of hydrogeochemistry to vector towards Pb-Zn mineralisation, which we re-investigate here using new geochemical baselines to define more sensitive, aquifer specific anomalies.
This approach characterises hydrogeochemical baselines for the major aquifer systems of the Broken Hill region (including the Proterozoic fractured rock aquifers and the Eromanga, Darling, Murray, and Lake Eyre Basins), using major, minor and trace element hydrogeochemistry. Several approaches have been used to define hydrogeochemical baselines to date. Pre-Selection methods filter a dataset to remove contaminated samples, while statistical approaches separate background and non-background populations via statistical tests. However, these approaches are often limited by subjective thresholds and apply to single parameters. The application of multivariate statistics (and in particular cluster analysis) presented here addresses these issues by considering the variance in all parameters and samples together, to build an understanding of the underlying hydrogeological processes and cluster geochemically related samples. These clusters are then interpreted with respect to independently assessed hydrostratigraphy to identify subgroups, which we interpret with high confidence as being diagnostic of specific aquifer systems. Using physicochemical parameters (i.e. T, EC, Eh) and stable isotopes, we demonstrate the robustness and geochemical sensitivity of the defined aquifer subgroups. These subgroups are then investigated for detecting geochemical anomalies relating to base metal mineralisation, by looking for the confluence of geochemical outliers of potential indicator species (such as Zn, Cu and δ34SSO4) within these sub-populations.
The opportunity to apply this multivariate baseline approach to target critical-mineral related systems, where groundwater is uniquely placed for distal detection (i.e. clay-hosted REEs, evaporative brines, sediment-hosted deposits) will be explored.
Abstract presented at the 30th International Applied Geochemistry Symposium 2024 (IAGS 2024)
