Abstract
This paper provides a review and synthesis of research literature on the geological, mineralogical and geochemical data to uranyl mineralization of the Arabian Nubian Shield (ANS). In general, the studied uranyl mineralization from the different locations of the ANS is similar from the mineralogical point of view. The mineral assemblages include, not conclusively, uranophane, kasolite, soddyite, boltwoodite, autunite, meta-autunite, liandratite, uranopyrochlore, ishikawaite and fergusonite. The compiled dataset supports a model of two main stages, namely hypogene or high-T alteration stage and supergene or low-T alteration stage. Both stages played an important role in the genesis of uranyl mineralization of the ANS. The late hydrothermal fluids leached uranium from the deep part of the host rocks and transported it in different uranous and uranyl complexes. While moving upward, the fluids gradually cooled to the temperature of meteoric water and probably have mixed with it. At these conditions, the pH of the fluids changes to be more alkaline and uranyl minerals start to develop in the fracture system mainly adsorbed on the clay minerals and probably coprecipitated with iron oxy-hydroxides. The requirement for supergene or low-T alteration stage would be saturation by oxic groundwater, a case implying the availability of meteoric water during the formation of uranyl mineralization in the ANS. Some of these minerals were dated by U-series method as 50-159 ka, and this could be attributed mainly to the Saharan II pluvial period.