Lithospheric architecture in the Archaean Dharwar craton, India: A magnetotelluric model

Abstract

The lithosphere beneath the Archaean Dharwar craton was investigated with an east–west oriented, 280 km long profile (from Yellapura to Sindhanur) with 22 magnetotelluric stations. Regional strike directions, estimated were −5° and 13° for the crust and the lithospheric mantle respectively. Our results indicate in western Dharwar craton, presence of low resistivity zones in the crust besides two significant upper mantle conductive features within the highly resistive Archaean lithosphere. We analyze the available geophysical data that include heat flow, seismic tomography and magnetotellurics (MT) from the Dharwar craton. Our inference supports to the existence of a thick lithosphere. A thickness of more than 200 km is estimated for the lithosphere beneath the Dharwar craton by our magnetotelluric model. The study has brought out the presence of lithospheric upper mantle conductive features in the depth range of 100–200 km bounded to the west part of the magnetotelluric profile. Significant variations in conductivity are seen on either side of the Chitradurga shear zone. The conductive feature in the depth range 120–150 km is related with kimberlite melts and the conductive nature in the depth range 160–200 km is explained by refertilization process, as craton passed over the Marion (ca. 90 Ma) hotspot.