Uranium in Australia

The bulk of uranium deposits in Australia can be classified as vein-type (sensu lato), which includes the massive new discoveries of the Alligator Rivers region in the Northern Territory, with indicated reserves of pitchblende already in excess of 350 000 tonnes of contained U3O8, as well as bodies of lesser size elsewhere in northern Australia and South Australia. Pitchblende is the most common primary mineral, refractory minerals such as davidite and brannerite predominating in some instances. The ores occupy zones of disruption or shear in metamorphosed Proterozoic rocks, and are generally considered to be of hypogene origin. The origin is most commonly thought to be by desorption of metal from Proterozoic metapelites during anatexis, or from granitic intrusives themselves of possible anatectic origin. Sedimentary uranium akin to the Wyoming rolls is present in the Tertiary of South Australia, where the uranium has been leached from Lower Proterozoic uraniferous inliers. The Carboniferous of central Australia contains sandstone-type deposits that have been subsequently folded and mildly metamorphosed. In Western Australia, and to a lesser extent possibly in central Australia, sedimentary uranium has accumulated in deposits of calcrete that have been formed by replacement of valley-fill deposits in fossil Tertiary drainage channels that contain evaporites. Two unique deposits occur; at Mary Kathleen, where pitchblende is present in allanite in a scapolite-diopside-garnet breccia-conglomerate of Middle Proterozoic age; and the Maureen, where uranium-fluorine-molybdenum mineralization is found in Carboniferous basal standstone. Uraniferous pegmatites are widely distributed, but have yielded no economic deposit of uranium. Proterozoic conglomerates have been extensively tested, but only thorium minerals have so far been discovered. (author)