Cretaceous-Eocene phosphorites, Taba Area, Sinai, Egypt: Comparative petrologic
and geochemical studies.
Ahmed M. El Shishtawi, Ibrahim A. Salem,
Ibrahim E. El Assy1 and Gehan A. Aly
Geology Dept., Fac. Of Sciences Tanta Univ.,1Nuclear Materials Authority,
Cairo, Egypt |
Phosphorites of Sudr Formation (Upper Cretaceous) and Thebes Formation (Early Eocene) of Taba Village and Wadi Taba areas, SE Sinai, Egypt, are associated with limestone, chalk and chert. Petrographically, phosphatic components of the rocks are skeletal and peloidal clasts, with calcareous biogenic debris, ferruginous materials, authigenic chalcedony quartz, gypsum and occasional fine-detrital grains. The main phosphate mineral is carbonate fluorapatite, with gangue minerals (identified by XRD and IR) of quartz, calcite, dolomite, gypsum and halite. The average
P2O5% of this phosphorite is 17.18% in the Up. Cretaceous of Taba Village. It is 19.2% and 11.82% in the Wadi Taba Up. Cretaceous and L. Eocene respectively.
The RRE and uranium contents, as well as the relationships between P2O5
and the major and trace elements were also studied. They indicate differences between Cretaceous and Eocene phosphorite.
Genetically, mechanical enrichment and concentration of phosphatic allochems occurred during periods of low sea level stands in shallow, moderate-to-high energy, marine environment. Winnowing and reworking of finer materials have provided the suitable conditions for concentration of phosphorites.
Comparison between the phosphorites of Taba Village (Up. Cretaceous) and Wadi Taba (Up. Cretaceous - L. Eocene) indicates that Cretaceous phosphorites are rich in P2O5 , SiO2 , U and some other major and trace elements than the Eocene phosphorites.
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