Uranium series disequilibria in the sedimentary uranium deposit at Yeelirrie,Western Australia

The weighted mean values of the ²³⁴U/²³⁸U and the ²³⁰Th/²³⁴U ratios in ore samples collected above the modern water table of the Yeelirrie uranium deposit in Western Australia are 1.38 ± 0.10 and 0.83 ± 0.28, respectively. The relatively larger variability in the latter ratio is evidence for the translocation of uranium subsequent to deposition. Daughter product separation is due to differences in the mobilities of the thorium and uranium species. Factors involved in interpreting the observed ratios, in terms of the dynamics of the accumulation of the deposit, are assessed in terms of an open system model. The observed disequilibria provide a quantitative basis for the evaluation of hypotheses developed from geological and other considerations.