Geochemical and mineralogical analysis of the Upper Cretaceous dolomitic phosphates at Queih Mine, Quseir, Central Eastern Desert, Egypt: depositional environment implications and pollution indices

Abstract

Soon for the security of phosphorus world supply, which comes primarily from non-renewable sources, the moderate carbonate phosphates will need further geochemical multidiscipline investigations to participate in the phosphorous supply chains necessary to increase human productivity. Dolomitic phosphates represented the main carbonate phosphate rocks of the Upper Member of Duwi Formation, at Um Queih Mine, South-Western Quseir, that phosphate can be classified as intermediate grade phosphate ore. It was enriched in V, Ni, Mo, U, Cu, Cr, Cd, Co as well as Zn and their ratios indicated that the deposition occurred in anoxic environment (reducing conditions). Mineralogical investigations indicated that the studied phosphorites are composed of two main mineral phases; fluorapatite and non-phosphatic minerals (dolomite, calcite, pyrite, gypsum, and quartz). The petrographic examination revealed that these phosphorites are composed of phosphatic lithoclasts, phosphatic bioclasts, opaques, and quartz grains embedded in a cryptocrystalline phosphatic matrix. The parent rocks of the studied phosphorites represented by basaltic mafic provenance were affected by low chemical weathering and deposited under marine anoxic environment. The mineralogical and geochemical characteristics indicated that the studied phosphorites deposited in marine anoxic condition. The weathering of these rocks can be harmful to the surrounding environment owing to its content of pyrite and potentially toxic elements (PTEs), the EF (enrichment factor) gives extremely high enriched with Mo, Cd, and Se.