The Role of Rock Alteration in the Distribution of Uranium and Associated Elements in the Um Bogma Formation at Wadi Nasib Area, Southwestern Sinai, Egypt.

Abstract

The Lower Carboniferous Um Bogma Formation in Wadi Nasib area is underlain by the Adediya Formation and overlain by El Hashash Formation. It consists of three members made up of variably abundant siliceous, argillaceous and calcareous rocks together with ironstones. These members show remarkable lateral variations in thickness and lithology. The formation hosts mineralization of radioactive, trace and rare elements in addition to base metals. The Um Bogma rocks and their altered products in Allouga, Abu Thor and Talet Seleim localities were subjected to extensive field and laboratory studies in order to determine the nature of the different alteration processes and their relative roles in the genesis and distribution of the radioactive and trace elements mineralizations. The petrographic examinations revealed that rocks of the Um Bogma Formation in Allouga locality are represented by siltstones, mudstones, sandstones, limestones and dolostones. In Abu Thor locality, the succession consists of claystones, siltstones, gibbsite, limestones and dolostones, whereas it is made up of claystones, siltstones, limestones and dolostones in Talet Seleim locality. The Um Bogma altered rocks consist of large assemblages of essential and accessory minerals of mixed primary and secondary origin. Their heavy fractions are rich in radioactive and trace- and base metals- bearing minerals. The distributions of these minerals vary among the different rock types and localities. In Allouga, the assemblage contains uranophane in addition to the radioactive -bearing minerals zircon,