The role of clay adsorption in genesis of uranium ores

Experiments are described in which: 1) The distribution coefficient (Ksub(d)) of uranium between a simulated ground water (containing 100 μg/l uranium) and kaolinite, measured over the pH range 3.5 to 10, was found to reach a maximum of 35,000 at pH 6.5. 2) Sequential adsorption-reduction has been demonstrated as one mechanism whereby the enrichment of kaolinite by uranium can exceed 0.01%, the level predicted from Ksub(d) measurements when solutions contain <=100 μg U/1. The relevance of these results to current models for genesis of ores from the Alligator Rivers Uranium Field is to supply a mechanism for generation of economic deposits from waters containing very low levels of uranium. These results also suggest reasons for the antipathy observed between uraninite and base metal sulphide occurrences in the Alligator Rivers Field. (author)