Geochemical Constraints on the Genesis Phosphorites of Chhattisgarh Basin, Durg District, M.P., India

This paper documents the geochemical and mineralogical characters of the phosphorite of Charmuria Formation (Chhattisgarh Basin). X-ray diffraction studies have revealed presence of carbonate fluorapatite as the only apatite mineral in this phosphorite, along with quartz as major gangue, and kaolinite-illite, calcite and pyrite in subordinate amounts. Structural formula of this apatite closely resembles carbonate fluorapatite. Further, CaO/P₂O₅ ratio (1.37 - 1.99) suggests that this phosphorite has not been affected by weathering. Quartz dominance over clay minerals and low CIA (24.79 - 46.87) is attributed to the tuffaceous nature of siliceous clays (lithofacies-A). The depletion of Sr, and trace elements of organic association in siliceous clays, phosphorite and phosphatic siliceous clays point to a common provenance.