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Volume :17 Issue : 1 1990
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Composition and origin of black shales from Quseir area, Red Sea, Egypt
Auther : A. M. EL-KAMMAR, M. DARWISH, G. PHILIP AND M. M. EL-KAMMAR
Department of Geology, Faculty of Science, Cairo University, Giza, Egypt
ABSTRACT
Black shales, occurring mostly within the Dakhla and Duwi Formations in the Quseir area are rich in organic matter. They can be described as bituminous calcareous foraminifera1 claystone to bituminous argillaceous limestone. In places, the black shales are abnormally enriched in vanadium (0.8% V2,05,) and other heavy metals, most markedly so near the contact with the Duwi Formation. The content of vanadium appears to be unaffected by the prevailing weathering. The black shales are composed of disordered poorly crystalline kaolinite, smectite, organophilic smectite, mixed-layer smectite-illite, quartz, calcite, ferroan dolomite, carbonate fluorapatite, gypsum, anhydrite, pyrite and organic compounds (mostly unsaturated molecules). The trace element content is classified into (a) a terrigenous association where Y, La and Ce are accumulated by clastics of biogenic origin; Ti and Zr in detrital minerals; Sc, Ga and Nb in kaolinite, while Co is mostly in smectite, (b) a carbonate association, including Pb, Sr and Mn, and (c) an organic association which includes Cd, Be, Zn, V and U. The U and Th equilibrium constants suggest no secondary radioactive enrichment. The organic matter belongs to kerogen type I1 approaching type I, indicating deposition from a highly productive marine environment under anoxic bottom water. The black shales are a good energy donator and can produce an excellent clinker upon pyrolysis.