A Comparison Of The Geological Features Of Uranium Deposits Found In Namibia And In Colorado

This article is a comparison of the uranium deposits in the uranium corridor of Namibia and theColorado uranium province in North America. The desert geology of the Namib consists of seasof sand near the coast. The state of Colorado is landlocked and has old and well-known uraniumprovinces as described by Finch,1996.The uranium deposits in Namibia that will be discussed are granite hosted uranium deposits(primary); sedimentary hosted uranium deposits (secondary) or a combination of the two but allof the uranium is sourced from granitic rocks called alaskites. The granite-hosted uraniumdeposits in Namibia include the low grade large tonnage R ssing deposit with mineralizationmainly hosted in alaskites as disseminated uraninite or pitchblende, the Husab uranium minewhich was recently opened, the Valencia uranium mine which has similar mineralization andgeology to the R ssing deposit and the Etango deposit which was previously called theGoanikontes deposit. The R ssing deposit is a world class intrusive associated uranium depositthat has many large ore bodies and some ore bodies in this area have uraninite as the mainuranium mineral.Offshore marine deposits off the coast of Namibia consisting of diatomaceous muds deposited inpalaeochannels extending100km into the ocean contain uranium mineralization with gradesunder46g/t U. Other sedimentary hosted palaeochannel uranium deposits in Namibia includethe Langer Heinrich deposit which is currently being mined, Tumas-Tubas deposits wheremining operations are on hold because of low uranium prices. The Omahola deposit (whichconsists of the Tubas Red Sand deposit, Ongalo alaskite, Inca deposit and a magnetite depositcontaining uranium) has uraniferous mineralization hosted in pedogenic lithologies, intrusivealaskites and unconsolidated sediments.The uranium ore deposits in Colorado discussed in this article are sedimentary hosted (roll-frontand tabular) deposits, as well as solution-collapse breccia pipe uranium deposits. Other areas inColorado consist of more than one deposit type such as the San Juan Basin which has sandstonehosted roll-front and tabular deposits that were later redistributed as high grade deposits intoveins along faults in Late Cretaceous and Early Tertiary times in conjunction with the LaramideBelt Deformation (Finch,1996).. Finch states that the redistribution of the primary uranium orestook place after the beginning of the Laramide Orogeny about70Ma. The Laramide orogeny isgenerally considered to have been the wave of compressional tectonism that reshaped thewestern North American continent from the west toward the east during latest Cretaceousthrough early Eocene time (Tectonic Evolution of Western Colorado and Eastern Utah, D. L.Baars and G. M. Stevenson). The Colorado Plateau Uranium Province is dominated by sandstonedeposits hosted by Upper Paleozoic and Mesozoic fluvial sedimentary rocks with three majorepochs of uranium mineral formation derived from a volcanic island arc (siliciclastic volcanics)at the west edge of the North American continent (Uranium Provinces of North America, WarrenI. Finch). Finch also states that the third and final formation of uranium mineralization in Colorado was around135Ma, after sedimentation of the Upper Jurassic Morrison Formation.The study of the tectonic history of South-western Africa has revealed that uraniummineralization in this area is related to volcanism resulting from intrusion of granites andgranitoids into basement rocks during the oblique subduction of the Kalahari Craton under theCongo Craton. As for Colorado, plate tectonic studies in North America indicate that uranium inthe area is directly related to volcanic activity along the western margin of the North Americanplate as stated by Finch, et al. Rainfall is an important factor in uranium precipitation anddeposition of uranium minerals in both Namibia and Colorado, especially with sandstone-hosted,palaeochannel and roll-front deposits controlled by reduction‐oxidation zone. Namibia currentlyproduces more uranium than the whole USA.