Trace Element Geochemistry of Black Shales in Singhbhum Mobile Belt, Eastern India: Implications For Source Rock and Paleoredox Conditions

Studied black shales from Singhbhum Mobile Belt (SMB), eastern India are enriched in chalcophile elements such as Cu, Ni, Co, V and Cr and radioactive elements such as Th and U relative to North American Shale Com- posite (NASC). Their chondrite normalized light rare earth element (LREE) enrichment and heavy rare earth element (HREE) deple- tion indicates that the rare earth element (REE) concentrations decreased gradually from Gd to Lu rather than severely affected by the diagenesis and weathering processes. The comparison of immobile element ratios (Th/Sc, Th/Co, Th/Cr, Cr/Th, and La/Sc) of studied samples with those of sediments derived from felsic rocks, basic rocks, Upper Continental Crust (UCC) and Post Archean Aus- tralian Shale (PAAS) showed that the source of studied shales were generally felsic in nature. High U (0.39 to 11) content, significant negative Ce anomaly and ratios (Ni/Co, V/Cr and V/(V+Ni)) supports in favour of their reducing depositional environment.