Effective exploration for uranium in South Australian palaeochannels

Extensive research into improving exploration methods for uranium in South Australian palaeochannels was conducted by CSIRO in the 1980s. The results of that work came out around the same time as the industry closed shop and thus the conclusions were not well publicised. Essentially, the work showed that groundwater was a powerful tool for locating uranium deposits in palaeochannels in regional exploration but that detailed analyses of multi-element data were required to interpret the uranium data properly. Further, lead isotopes could be used to confirm the groundwater interpretations. The research found that many South Australian palaeochannels are characterised by highly saline and often acidic waters. Such waters readily mobilise radium, a daughter of the uranium contained in the local aquifer rocks. If these waters come to the surface then radiometric anomalies can be generated that are unrelated to uranium deposits. An example of such an anomaly, covering over 100 km², occurs in the Great Victoria Desert of South Australia in the vicinity of Lake Maurice. As a consequence of this enhanced radium mobility, methods of exploration based on uranium-daughters such as measurement of radon at the surface and downhole gamma-logging were not recommended. The intervening years since the original work has lead to improvements in methods that make application of these recommendations more available. More accurate analyses by ICPAES and ICPMS provide better groundwater data sets and uranium analyses are no longer only available in specialist laboratories. Commercially available software and extensive development of thermodynamic databases of uranium aqueous species make solution chemical modelling now more available and more accurate. The models used, particularly for saline waters, however, remain unchanged. Finally, lead isotopes can be measured by ICPMS, making this more available and cost-effective for confirming other interpretations.