Radon Emanometry Case Studies in Namibia: the Spitzkoppe and Tumas Uranium deposits

The RadonXTM technique uses the principle of adsorption of radon, emanating from buried uranium mineralization, onto activated charcoal. The charcoal is contained within a cartridge which is fitted into the base of an inverted cup, and is buried in the ground for a period of approximately 10 days. The technique differs from alpha-sensitive radon detection systems in that it measures the gamma radiation arising from the daughter products of the adsorbed radon, namely 214Bi and 214Pb. Two case studies are presented, dealing with the detection of partially buried shallow uranium deposits, using the RadonXTM radon emanometry technique. The case studies are sited over the Spitzkoppe and Tumas deposits in the Central Zone of Namibia, comprising uranium mineralization contained in shallow calcretized palaeo-valley gravels buried under a thin cover of calcrete or gypcrete duricrust. The results show that both deposits have clear RadonXTM target anomaly signatures, in large part correlating with the higher grade areas. The technique is thus an effective and essential adjunct to gamma spectrometric surveys in surrounding areas of cover. Although these deposits are shallow, with a depth extent of up to ~20 m, case studies in other areas show an excellent depth of penetration, of 100m or more, under favourable permeability conditions.