The occurrence of uranium in the Katanga System of northwestern Zambia

Abstract

Until recently, occurrences of uranium in the Katanga system of late Proterozoic age were known only in the Shaban province of Zaire, as at Shinkolobwe, and in the Zambian Copperbelt. A survey by AGIP has now shown the existence of uranium mineralization in northwestern Zambia in similar rocks. This mineralization occurs mainly in mica schists underlying a quartzite horizon near the base of the Lower Roan formation at the margins of the Kabompo, Mwombezhi, and Solwezi domes. The mineralization occurs as disseminations or as veins of thorium-free pitchblende, and as secondary uranium minerals. Several of the occurrences have been investigated by drilling which intersected scattered mineralization of good thickness and grades. The economic significance of this new uranium province is still under study.Uranium occurrences in the Katanga system of the Shaban and Zambian Copperbelts were earlier thought to be of magmatic origin and to belong to a metallogenic epoch independent of the copper-cobalt mineralization. A deposit at Shinkolobwe was in fact classified as of typical endogenous type. It is here suggested that all the known uranium occurrences in the Katanga system in the Copperbelt and domes areas are of sedimentary syngenetic origin like the copper and cobalt mineralization. In the three areas described, i.e., Shaban and Zambian Copperbelts and the domes area, copper and uranium mineralization is found in the Lower Roan formation in the lowest part of the Katanga system in similar environmental conditions and stratigraphic controls but areally localized according to a regional metal zoning pattern.Tectonic deformation during the Lufilian orogeny and metamorphism related to and subsequent to the orogeny gave rise to epigenetic vein-type uranium deposits by the repeated mobilization and redeposition of the original mineralization. Supergene alteration and thermal events resulted in further redistribution and concentration.