Investigation of Redox, Provenance and Tectonic Setting of Organic Carbon-Rich Rocks from the Himmetoğlu (Bolu/Turkey) Field

Among the terrigenous sedimentary rocks, shales are considered to represent the average crustal composition of the provenance much better than any other siliclastic rocks. Shales retain most of the mineral constituents of the source and their bulk chemistry preserves the near orginal signature of the provenance and more faithfully reveal palaeoweathering conditions. The present study examines the geochemistry of organic carbon-rich shales and coals. Study area is the Himmetoglu coal and bituminous shale basin in Goynuk (Bolu) district. The stratigraphic section from bituminous shales and coals were collected 38 samples. Organic geochemical (Rock-Eval/Corg), inorganic geochemical (X-ray fluorescence, XRF), and mineralogical studies (scanning electron microscope, SEM and X-ray difraction, XRD) of samples were performed, and to these investigations have been made an approach the redox conditions of depositional environments, their source rocks, paleoweathering and tectonic setting of the provenance. Degree of pyritization (DOP) values, V/V Ni (0.11-0.91) and U/Th ratios (0.44-17.85) of the bituminous shales and coals suggests that anaerobic, or euxinic, dysoxic-anoxic and suboxic-anoxic redox conditions respectively. Mean major elemental composition of the bituminous shales and coals is in fair concurrence with that of the Average shale, North American Shale Composite, Upper crust, and Post-Archean Average Shale. Chemical index of alteration investigations imply weak weathering of the source material that constitute both bituminous shales and coals. Plots of bituminous shales and coals on tectonic setting discrimination diagram reveal an active continental margin setting for the provenance.