Bulk rock and mineral chemistry of meta-sediments from Mahakoshal Supracrustal Belt, Central Indian Tectonic Zone: constraints on weathering, provenance, paleoclimate and metamorphism

Abstract

The Mahakoshal Supracrustal Belt (MSB) is located at the northern boundary of Central Indian Tectonic Zone (CITZ). The Volcano-sedimentary succession of MSB is underlain by the basement Sidhi gneiss and Dudhi granitic gneiss and overlain by later intrusives, compositionally varying from granitoids to monzodiorite-quartz-syenite to syenite. Present study involves detailed bulk rock geochemical and mineral chemical studies of the fine clastics from this volcano-sedimentary sequence. This study indicates that fine clastics of MSB have wide range of chemical characteristics, which may indicate mixed precursors. In comparison with established shale standards (Post-Archean Average Shale, North American Shale Composite), it can be inferred that all these fine clastics have mixed precursors. An important observation is that all these clastics of Sleemanabad, Parsoi Formation (Fm) are immature sediments derived from least altered source rocks and have witnessed insignificant post-depositional perturbations, except for the Garnetiferous schists exposed near the southern margin of Mahakoshal Supracrustal Belt. Therefore, their elemental signatures may reflect pristine characteristics with mixed intermediate-mafic precursors for Sleemanabad Fm, at Sidhi, and dominantly felsic to intermediate precursors for the rest of the groups including Parsoi Fm, Garnetiferous schist, Sleemanabad Fm, at Jabalpur. Based on mineral chemical data for the Garnetiferous schist, calculated temperature for metamorphism using garnet-biotite thermometer ranges from 434° to 635 °C with a minimum average temperature of 510 °C and using Ti in biotite geothermometer are 550 °C and 600 °C. It is inferred that the possible repositories for all the parental masses are from the CITZ, therefore, the catchment of MSB basin was restricted within CITZ. It is also geochemically ascertained that the entire sedimentation within this basin took place in oxygen-rich, semi-arid to arid climate, thus concordant with globally recorded Paleoproterozoic oxygenation event.