الفهرس 
LithostratigraphyOnly 14 pages are availabe for public view
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Abstract
Sinai phosphates belong to Matulla, Sudr Chalk and Thebes formations of Upper Cretaceous <U+2013> Early Eocene age. Sinai phosphate beds are well exposed in three localities namely; ElSheikh Attia, Wadi ElQuseiyib and Taba areas. Three stratigraphic sections were described, measured and sampled. The detailed petrographic study of phosphate samples from the study area show that they are composed mainly of three constituents; phosphatic particles, nonphosphatic particles, and cementing materials. The mineralogical constituents of phosphate beds were investigated using Xray diffraction analysis. The obtained results reveal that carbonate <U+2013> fluorapatite (francolite) is the only phosphate minerals in the phosphate rocks of the study area. Calcite and quartz are the dominant non phosphate minerals. Gypsum , anhydrite dolomite and halite occur in minor amounts. P2O5 values which are obtained with an average of about 12.45, 17.6 and 7.85 % for Matulla, Sudr Chalk and Thebes formations respectively. The average contents of uranium in the phosphate samples collected from ElSheikh Attia, Wadi ElQuseiyib and Taba areas of Sudr Formation are 62.0, 72.0 and 44.0 ppm respectively. This study threw new light on the origin of phosphates by proving the important role of bacterial mediation in the process of phosphogenetic .The origin of phosphates in the study area can be summarized by the following :1 The source of phosphorus is Tethyan ocean reservoir had accumulated and upwelling current bring the phosphorus from deep ocean into the photic zone.2 The phosphorus carried out by upwelling currents promote the flourish of a large quantities of plankton 3 Upon death, planktonic organisms and fecal material sink to the bottom of basin of deposition.4 The organic matter subjected to bacterial degradation. Bacterial action is very important in phosphgenic process on two levels: (a) Bacterial release phosphorus from organic matter. (b) They are capable of concentrating and precipitating phosphate. 5 Reworking of the accumulated phosphate deposits within the sediments concentrate phosphate particles occur in response to changes of current pattern or relative sealevel. 6 Cementation of phosphatic material is a common final step. The phosphorite have been cemented by carbonate and silica