Geochemical Characterization of the Upper Cretaceous Duwi Phosphorites in the Beida Mine, Central Eastern Desert, Egypt: Implications of P₂O₅ - F - U Interrelations

Abstract

Integrated petrographical, mineralogical and geochemical studies were carried out on the phosphate beds of the Duwi Formation, which was exposed at the Beida mine. Petrographically, the investigated phosphatic microfacies are Molluscal bioclastic phosphatic grainstone and Biopeloidal phosphatic grainstone, generally composed of phosphatic pellets of collophane and bioclasts bone and teeth fragments indicating a high-energy near-shore depositional environment and formed authigenically within oxic to suboxic zones from phosphate-rich sediments. The main mineralogical constituents of the considered sample are phosphatic minerals including dahlite, francolite and hydroxylapatite, while the non-phosphatic minerals are quartz, calcite, halite and ankerite. Geochemical studies reflect that the phosphorites in the Beida mine obtain medium-grade ore with an average of 25.01 % P2O5. The significant correlation between P2O5 and U reflects that the U may be present in the apatite crystal lattice. The more considerable values in the calculated uranium rather than measured uranium could be attributed to the post-depositional enrichment of uranium.