Electrical conductivity structure along a few transects over the Indian Lithospheric domains

Abstract

This paper presents a brief review of the electrical signatures of the subsurface structure of the Indian lithosphere along a few transacts across some of the important geological provinces using modelling results from magnetotelluric (MT) studies. The case studies discussed here includes the Himalayan collision zone, Deccan Volcanic Province, Narmada-son Lineament zone, Dharwar and East India Cratons, Southern Granulite Terrain (SGT). The subsurface electrical models discussed are mostly from broad band and long period MT studies, providing deeper structural information. In the Himalayas, the thrust system, mainly the Main Central Thrust and Indus Tsangpo Suture Zone are reflected as low resistive zones. Several hidden basement fractures/faults are identified in the Deccan Volcanic Province, some of which might have facilitated magma spreading vertically as well as horizontally. The MT models provided a broad view of the plumbing geometry of the Deccan volcanics. An Archean suture zone has been identified in the western Dharwar carton. Electric Moho has been delineated in the Eastern Indian Craton suggesting absence of conducting continental lower crust in this region. MT models in the Kutch region imaged a fluidized zone to which the observed seismicity in the region is shown to be confined. In the south, the Achankovil Shear Zone (ACSZ) in the SGT is reflected as a well-defined north dipping conductive structure, which might have played a significant role in the subduction-collision tectonic processes of the region. Largescale 3D cooperative modelling studies coupled with seismological and gravity models is the key approach to derive a geologically meaningful model of the lithospheric structure, a way forward.