Three-dimensional crustal resistivity image of the central Indian tectonic zone, India: derived from magnetotelluric studies

A few seismic and 2D resistivity models were presented in the past to understand the tectonic setting of the Central Indian Tectonic Zone (CITZ) comprising the Narmada-Son Lineament (NSL) zone. The region is highly disturbed and bounded by several known and unknown faults, namely, Barwani Sukta Fault, Gavligarh Fault, Kaddam Fault, Narmada South Fault, Purna Fault, and Tapti Fault, both shallow and deep-seated. In view of the presence of large number of tectonic features in the area, it seems necessary to perform the 3D inversion of MT data. Broadband MT data were acquired at 273 stations in different phases in a gridded fashion between 74.76 and 78°E and 20°40 ’ to 22.5°N to image the CITZ. Although, few 2D studies were done earlier this is the first 3D study of the central region of CITZ, to derive the 3D subsurface resistivity model of the study area. The derived 3D resistivity model delineates several major crustal conductors, fault boundaries, and the resistive basement. We correlated the present 3D resistivity model with previous magnetotelluric and deep seismic sounding profiles of the region. The deep-seated conductors (∼10 Ωm) correspond to the underplating of mafic magmatic and/or fluid intrusions during the Cretaceous-Tertiary Deccan volcanism and are controlled by the deep-seated faults. The shallow depth localized faults support the upward movement of fluid present. The resistive structure (>1000 Ωm) corresponds to the basement. The study shows a basement uplift between the Narmada and Tapti rivers. The high heat flow, high seismic velocity, and low-resistivity structures correlate with mid to lower crustal conductors associated with the magmatic underplating and major fault zones in the NSL. These correlations help to study and interpret the characteristics and behaviour of faulting in the region.