Applications of groundwater geochemistry to genetic theories and exploration methods for Early Tertiary sediment-hosted uranium deposits in Australia

The geochemistry of groundwaters in contact with U mineralisation of economic grade and tonnage which is hosted by Early Tertiary carbonaceous pyritic sands and clays in the southern Frome Embayment of the Great Artesian Basin, Australia, has been compared with the geochemistry of groundwaters from three sub-economic or non-mineralised prospects each of which has some geological similarity to the Frome area. The results suggest that enhanced U enrichment of sediments in the Frome area, compared with the three prospects, can be related principally to the presence of carbonate minerals. Also apparent in Frome area waters is a close correlation between groundwater U concentration and the ion activity product of Ca and SO4. This correlation can be used in U exploration as it demonstrates coexistence of reduced U minerals and pyrite via their oxidation products. A close correlation between U and co-leached F in groundwaters from a prospect where waters derive directly from Proterozoic basement rocks illustrates a relationship which can be used to identify groundwater U leached from non-economic rock-forming minerals. 25 refs.; 7 figs.; 1 table