Electrical imaging for thermotectonic architecture of the Paleoproterozoic Vindhyan rift basin and Malwa Plateau in central India: Evidence from magnetotelluric data

• The thermotectonic architecture beneath the Vindhyan Basin. • The Malwa Plateau uplift is a high-conductivity feature formed by fissure eruptions. • Enhanced conductivity in the upper-mid crust during the late K-Pg periods. Magnetotelluric (MT) studies are employed to investigate the electrical structure beneath the Paleoproterozoic intracratonic Vindhyan rift basin, which is overlain by Deccan basalts. Deep thermotectonic activity, a geological process responsible for shaping a complex subsurface architecture, is more clearly revealed along a north-south MT profile that crosses geological faults and the Malwa Plateau. Using 25 broadband magnetotelluric (BBMT) stations and the non-linear conjugate gradient (NLCG) algorithm, a 2D electrical model was developed. The significant resistivity contrast in the model, ranging from ∼0.1 to 5000 Ωm, indicates altered resistivity in the Vindhyan basin sediments, which are exposed below 100 Ωm. Uncertainties in the basin thickness indicated along the profile, where it is approximately 2 km thick layer of sediments beneath stations vin01-vin08, are deposited on a resistivity feature, R2. Four conductors (C1, C2, C3, and C4) with resistivities between ∼0.1 and 1 Ωm are identified in the upper-mid crust, where the central conductors indicate the uplift of the Malwa Plateau, approximately 100 km wide. The east-west oriented faults could represent the earliest faults of the basin, with the Basoda-Barsingarh fault situated at the center of the plateau. Additionally, the Kannod-Damoh Fault and Ratlam-Shivpuri Fault surround it to the south and north, respectively. The plume activity associated with the supercontinents Columbia and Rodinia might have triggered the reactivation of these ancient faults. As tectonically weak zones, these faults provide pathways for heat, melts, and fluids to rise from the Reunion plume head, resulting in melting within the crust and upper mantle. The thermotectonic rejuvenation of the subsurface involves a crust-mantle boundary that becomes indistinct. Key factors contributing to increased crustal conductivity include carbonate-rich fluids trapped during the Paleoproterozoic, basaltic melts with fluid inclusions, and magmatic underplating during the late Cretaceous-Paleogene (K-Pg) periods. The melt fraction is estimated to range from 8% to 16% for each conductor with a bulk resistivity below 5 Ωm. As sulfides melt together with basaltic melts, they collectively boost the overall melt conductivity and decrease the partial melt fraction required to account for the high observed conductivity.