Structure and geodynamic evolution of the lithosphere below Northwest Indian Shield: Constraints from geological, geochronological and multi-scale potential field modelling

Abstract

The Northwest Indian shield (NWIS) comprises of Archean cratons such as the Bundelkhand (Bh.C), Marwar (MC) and Dharwar (DC), the intervening Proterozoic mobile belts, the Aravalli Delhi Fold Belt (ADFB), Narmada-Son Lineament (NSL) and the Vindhyan basin (VB), the Mesozoic Cambay (CR) and Kutch rift basin (KB) basins and the Saurashtra Continental Block (SCB). The region is covered by thick traps of Deccan Volcanic Province (DVP) thereby masking the geological structures. In this study, we carry out a seismically constrained multi-scale geopotential field interpretation along two long corridors that cut across major Precambrian terrains of the NWIS. The models reveal the Moho varying between 30 and 45 km and LAB between 120 and 180 km. The derived crustal architecture shows that i) the ADFB and NSL are bounded by deep crustal faults having denser crustal rocks, ii) shallow Moho below DVP and CR, iii) presence of thick underplated layer at the base of lower crust in the entire region indicating a strong magmatic imprint. Correlation of modelled lithosphere structure with the structural geological and geochronological data across different terrains of the region suggests that the localized thickening of lithosphere below the ADFB and NSL could be the imprint of paleo-subduction during Proterozoic period, whereas, the thin lithosphere observed below NWIS as a whole represents lithosphere delamination caused by two major LIP events such as 800 Ma Malani and 65 Ma Deccan events. Hence, the proposed evolutionary models across the Precambrian terranes adequately explain the geopotential observations with linkages to present-day lithosphere below NWIS.