The redistribution of uranium with weathering in the Koongarra Uranium Deposit

Abstract

In unaltered quartz chloride schist, uranium was mainly in uraninite (UO2), which occurred in zones, fissure coatings and veinlets. The apparent diffusivity of uranium into chloritic schist from fissures was estimated to be about 10-18 m2/s. Penetration into other fissure coating material was greater than into the chlorite matrix. In slightly weathered rock, areas of iron oxidation showed increased levels of dispersed uranium. Fronts of iron oxidation appeared to move preferentially along chlorite veins, accompanied by uranium and iron enrichment. Uraninite in this core showed signs of early in situ alteration of uraninite to secondary uranium minerals. In weathered rock, alpha activity was more strongly associated with manganese oxide nodules than iron oxides nodules, followed by dispersed iron oxides coating clays, and then clays.