Geology and Geochemistry of the Phosphorite Deposits, Sibaiya Area, Nile Valley, Egypt

The present work aims to study the phosphorite deposits of the Late Cretaceous age that are belonging to the Duwi Formation. It is well exposed in Sibaiya area as oxidized phosphorite with yellowish to brown colour and non-oxidized phosphorite in some parts with grey to black color. This Formation could be classified into lower phosphorite, middle shale and upper phosphorite members. The lower phosphorite member is the most economic one. The average thickness of this member is 3.3 m in the western part, while it reaches 4.8 m in the eastern part of Sibaiya area. The phosphate beds are composed of peloids, Bioclasts of bone and teeth fragments and Coprolites. A geochemical analysis were done for, CaO, P₂O₅, SiO₂, Fe₂O₃, MgO in% in addition to heavy metals Cd, Cr, Cu, Ni, Sr, Zn in ppm as well as U, Th and Ra in ppm. The results show that the average of P₂O₅ and U contents in oxidized phosphorite are 24.18 % and 69 ppm respectively. Meanwhile in non-oxidized phosphorite, they are 27.8 % and 85 ppm respectively. The variation in P₂O₅ and U contents in Sibaiya phosphorite rocks are probably related to depositional and digenetic aspects. Generally, the Sibaiya phosphorite could provide an economic value for production of phosphoric acid and extracted of U as by- product