P2O5 – F- U Characterization and Depositional Environment of Phosphatic Rocks for the Duwi Formation, Qussier- Safaga Region, Red Sea Coast, Egypt.

Abstract

Abstract The Duwi Formation in Qusseir-Safaga region is conformably overlain by the Qusseir variegated shales and underlain by the Dakhla shales. The studied phosphatic rocks in the Duwi Formation, is an attractive rock unit for it’s enrichment in heavy metals and U content. Mineralogically, phosphatic rocks in the Duwi Formation are mainly composed mainly of fluorapatite, in addition to minor occurrence of calcite, dolomite, gypsum, quartz, and pyrite. Geochemical data reveal that the rocks of the Duwi Formation were deposited under anoxic environments. The present study used the statistical result of the interrelation between P2O5, F and U concentrations on Egyptian phosphate samples and compared to the measured data. Uranium mostly occurs in an oxidized U 6+ state. It could be fixed with the phosphatic ion, forming secondary uranium phosphate minerals such as phosphuranylite and belovite in Qusseir region. In addition to Uranyl phosphates, uranium minerals in Safaga region contain also Uranyl carbonates and Uranyl sulfates, which had been attributed to the post-depositional U enrichment. The chemical data and index show that the phosphatic rocks in Safaga region are more enriched in the majority trace and rare earth elements, and are subjected to high chemical weathering than those in Qusseir region.