A non-uniform thin sheet model for geomagnetic induction anomalies in central India

Abstract

A non-uniform thin sheet model has been developed to account for the geomagnetic induction anomalies revealed by a magnetometer array study over central India. The conductance distribution map indicates three conductive zones; the first beneath the Satpura, the second appearing as a NW-SE continuation of the Godavari graben, and the third an arcuate conductivity zone in the vicinity of Sehore. The surface and near-surface sedimentary basins, known from earlier gravity and deep seismic sounding studies, cannot provide the estimated conductance for the different conductors. Collation of a variety of geographical data, including heat flow, suggests that heat fluxes characterizing the region are sufficient to cause partial melting at the crust-mantle interface and to initiate metamorphic dehydration leading to a release of fluids at mid-crustal levels. The characteristics of the regional gravity anomaly—absence of a low-velocity zone at the base of crust, as against the presence of the large number of a discontinuous reflectors in the mid-crust — favour a fluid phase as the likely mechanism for the mapped high-conductivity zones.