Geochemistry, mineralogy and depositional environment of black shales of the Duwi Formation, Qusseir area, Red Sea coast, Egypt

• Esmat A. Abou El-Anwar ^[1] ; H. S. Mekky ^[1] ; W. Abdel Wahab ^[1]
  1. [1] Geological Sciences Department, National Research Center, Giza
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 34, Nº. 3, 2019, págs. 883-892
• Idioma: inglés
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• Resumen

  • This study focuses on the geochemistry of redox-sensitive elements of marine black shales at the Qusseir area of the Duwi Formation to infer their depositional environment. The black shales from the uppermost member of the Duwi Formation in the Qusseir area is conformably overlain by the Qusseir variegated shale and underlain by the Dakhla shale. Detailed mineralogical and geochemical characteristics were examined using several techniques, including X-ray diffractometry, scanning electron microscopy and X-ray fluorescence. Mineralogically, black shales in the Duwi Formation are composed mainly of montmorillonite, kaolinite, calcite, gypsum, quartz and pyrite. They are detrital and authigenic in origin. They are most probably derived from basic volcanic rocks by intensive chemical weathering under the prevalence of semiarid conditions. The redox-sensitive trace metals suggest anoxic sulfidic conditions that favoured the accumulation of these metals in the Qusseir area of the Duwi Formation.