Document Type : Original Article
Departments of Geology* , Al Azhar university,
Egyptian mineral resources authority
Egyptian company for mineral resources
This paper deals with the study of the Mineralogical, Geochemical and Environmental deposition of Clays in Esna Shale at El-Buruk- El-Hassana and El- Himmah Baghdad areas, North Central Sinai, Egypt. The present work is based on the field and laboratory work carried out by present authors. sixty stratigraphic sections representing Esna shale unit in the study area were studied, measured and sampled. The laboratory work comprise 17 samples for XRD analysis to study the mineral constituents of the clay and argillaceous rocks and 36 samples for chemical analysis using XRF method to detect the major oxides SiO2, Al2O3, Fe2O3, CaO, MgO, TiO2, MnO, Na2O, K2O, SO3--, Cl-, P2O5 and L.O.I. and ten samples for the trace constituents, F, Ba, Cr, Cu, Li, Ni, Zn, As, B, Ga, Se, Y, V, Co, Rb, Sr, Nb, Mo, Sn, Sb, La, Yb, Hf, Ta, Pb, Zr and Ce. Montmorillonite and kaolinite are the main constituents of clays. The other associated minerals are quartz, gypsum, halite and dolomite. Geochemical speaking, SiO2, Al2O3, K2O and Na2O are controlled by the amount of montmorillonite, kaolinite and illite while CaO and MgO contents are controlled by calcite and dolomite which occur as minor constituents. The high and low contents of Fe2O3 and MnO respectively are attributed to the low oxidation potential that prevailed during the deposition of clay causing precipitation of Fe+2 keeping Mn+2 in soluble state. Esna Shale of the study areas are deposited in deposition environments changes from very shallow inner neritic zone to outer neritic zone.