Petrology and Geochemistry of Meso-Proterozoic Arenaceous Sediments of the Barapani Formation of Shillong Group in Parts of Meghalaya and Assam

In the Proterozoic Shillong Group, the Meso-Proterozoic arenaceous Barapani Formation, unconformably overlies the Paleo proterozoic Tyrsad Formation. Argillaceous quartz arenite, quartzite and quartz wacke are the constituents of Barapani Formation, in both Meghalaya plateau and Mikir Hilis in Assam. Samples from both the domains contain same type of detrital grains. Monocrystalline quartz forms about 70 to 90 % and feldspars and lithic fragments form minor part of the framework constituents. Sericite is the major mineral in matrix. Geochemical data (major and trace elements) of these arenites show overall similar elemental composition of all the samples from both Meghalaya plateau and Mikir Hills, Assam, indicating constancy of provenance. However, samples from the Mikir Hills as compared to that from Meghalaya Plateau show depletion in FeO(t), CaO, and MgO and enrichment in V, Cr, Co, Ni and Cu. Samples from both the Meghalaya plateau and Mikir Hills indicate a passive margin tectonic setting of sedimentation.