Petrography, Mineralogy and Geochemistry of Kuhkamar Shale in the Roum section (South of Qayen): Application for Provenance and Tectonic setting

The Kuhkamar shale with a thickness of 354 m is composed of siliciclastic rocks (sandstone and shale). Petrography studies of the sandstones in this area show two petrofacies including arkose and sub-arkose. These sandstones composed of sub rounded to moderately sorted; therefore, compositionaly to texturaly, they are immature to submature with mono and polycrystalline quartz and k-feldespar. In terms of petrography, the shales are rich in quartz, albite, calcite and, to a lesser degree, clay minerals (illite and chlorite). Moreover, SEM images represent clay minerals of illite and chlorite in these shales. In order to interpret provenance, the shales of the studied section have been geochemically analyzed. These shales are rich in quartz, albite, and calcite with small amounts of clay minerals (illite and chlorite). With respect to (UCC), these shales show depletion in SiO2 ،Al2O3 ،Na2O, P2O5, Ba, Cu, Nb and Sr and enrichment in U and CaO. Plotting Al2O3 versus TiO2 as well as ternary diagrams, (SiO2/20), (K2O+Na2O), (MgO+TiO2+FeO) and Al2O3, (CaO + Na2O + K2O), (FeO + MgO), suggest that the original source of these shale was from intermediate igneous rocks. Calculated PIA and CIA indicate low to medium chemical weathering and arid to semi-arid climatic conditions in the source area. Prepared discrimation diagram using the major oxides (SiO2 versus K2O/Na2O) and ternary diagram (Na2O+ K2O), (TiO2+ MgO+ Fe2O3), (SiO2/20), shows that most of these shales were plotted in active continental margin. Paleogeographic reconstruction in this area, during the Eocene, shows that sedimentation in this area is mainly taken place in the intracontinental subsiding basin.