Detrital Zircon U-Pb Geochronology and Lu-Hf isotope systematics from the Pranhita Godavari basin: Implications for the Provenance and Mesoproterozoic tectonics

Cratonic margin basins are crucial in tracking the provenance characteristics. This study aims to characterize one of the Proterozoic basins in Southeastern India known as Pranhita Godavari (PG) basin. Nestled between the famous Dharwar and Bastar cratons, the PG basin is about 450 Km long NW-SE trending rift-related basin with a huge thickness of siliciclastics. The basin consists of three cycles of deposition. In this study, we characterize the geochemistry, U-Pb geochronology and Lu-Hf systematics of the detritus as well as the adjacent basement Gneiss in order to define the sediment source.

                        K₂O/Na₂O v SiO₂ and the Discriminant function diagrams (Verma & Armstrong-Altrin, 2013) indicate a passive margin setting for the sediments. Together with Eu/Eu*, the high La/Yb_N ratios (8.23-37.9) and LREE enriched and flat HREE patterns indicate a felsic source. The other geochemical indicators like TiO₂ versus Zr and Ni, Al₂O₃/TiO₂, Th/Co, La/Sc ratios along with high Th/U also indicate felsic continental sources.   The different weathering indices like CIA.PIA, and  ICV indicate moderate to slightly intense weathering of the source terrains producing mostly mature sediments.

The metamorphic zircons (average Th/U=0.88) from the basement Gneiss yield a Concordia age of 2490±6 Ma and a weighted mean age of 2490±6 Ma. Three magmatic zircon cores yield a weight mean average of 2677±36 Ma. Previous studies from the Bastar and Dharwar cratons also report the presence of 2.5 Ga old zircons.

The sediment was mainly sourced from the Paleoarchean to Mesoproterozoic sources with detrital zircon ages spread from 3571-1622 Ma. The Probability Density Plots show major peaks at 1842, 2498, 2637 Ma and minor peaks at 1637,3340, 3567 Ma. The Youngest detrital zircon method brackets the maximum depositional age of the Mulug Formation 1622±33 Ma.

The zircons from the basement gneiss of Peninsular Gneissic complex show negative Hf isotope values (εHf= -15.27 and 0.17). Similarly, the detrital zircons show negative values (εHf =-12.58-0.70) indicating their derivation from evolved sources.

The age peaks and the εHf composition from the Mulug formation perfectly match with the basement gneiss ages. This together with published literature indicates that the Mulug formation was deposited at ~1.6 Ga and was sourced from the eastern Dharwar and Bastar cratons