Highly variable content of fluorapatite-hosted COin the Upper Cretaceous/Paleogene phosphorites (Morocco) and implications for paleodepositional conditions

Phosphorus (P) usually occurs as microcrystalline minerals of carbonate fluorapatite (CFA) in sediments upwelling-related areas. The Upper Cretaceous/Paleogene marine sedimentary rocks Morocco host the world's largest economic reserves phosphorus, which were deposited on eastern passive margin central Atlantic Ocean. However, a full petrographic, mineralogical and geochemical characterization Moroccan phosphate is yet to be determined. Here, we use optical scanning electron microscopies, X-ray diffraction, infrared spectroscopy, combination with microprobe analyzer document (CO32?) substitutions CFA from two distinct basins their possible implications for paleoenvironmental conditions. phosphorus-rich deposits predominantly comprise porous phosphatic peloids coated grains maximum size 500 ?m, turn consist high-density nano- micron-sized rod-shaped sphere-like crystallites. Bulk situ analyses reveal heterogeneous CO32?content at regional- grain-scale. Fourier transform spectra indicate that CO32?accommodates only site within structure, found other natural minerals. CO32?variations between basins, ranging 1.97 8.24%, are likely related depositional conditions – thus supersaturation respect during mineral formation, transport, redeposition. Moreover, some have revealed alternations CO32?-rich CO32?-poor laminae, pointing out local differences CO32?concentrations sediment pore waters. Interestingly, change shape diminution crystallites caused by high content CFA-hosted CO32?could possibly increased intragranular porosity, highlighting an underestimated role CO32?on grain morphology. Considering higher solubility than fluorapatite, application such specific areas rock powders may deep interest long-term soil fertilization. These results further evidence importance studying phosphorites economic, environmental, scientific interests.