Distribution and Genesis of Sedimentary Uranium Near Curnamona, Lake Frome Region, South Australia

Abstract

Exploration in the Curnamona area of South Australia has delineated two lower Tertiary paleochannels incised into Middle Cambrian red beds of the Arrowie basin. One of these, the Billeroo channel, contains pervasive uranium mineralization in sediments deposited in a braided stream draining northward off the Proterozoic Willyama Complex. One potentially economic uranium deposit, the Gould's Dam deposit, and several other significant uranium occurrences, have been located within the sands of the channel section. Detailed evaluation of the distribution of mineralization within the channel sands has revealed a clear relation among uranium mineralization, geochemical zonation, and the sedimentologic features of the host sands. A genetic model is proposed in which a uraniferous geochemical cell migrated down gradient through each sand of the channel section. The resulting partly-discrete cells were preferentially guided through areas of high transmissivity, corresponding to the main channels of the braided stream. Under favorable conditions uranium was deposited at the redox interface of the geochemical cells developed along the edge of these channels adjacent to and within the less permeable, more reducing longitudinal-bar deposits of the braided stream. The geometry and geochemistry of the resulting mineralization are very similar to that of roll-front uranium deposits in Wyoming.