Gravity modelling across satpura and godavari proterozoic belts: Geophysical signatures of Proterozoic collision zones

The modelling of a gravity profile across the Satpura Fold Belt (SFB) constrained from seismic and other available information, suggests that the gravity high observed over the SFB is caused due to high-density upthrusted blocks of lower crustal rocks in the upper crust exposed in some sections, and the gravity low towards the south of the Central Indian Shear (CIS) is caused due to low-density rocks below the Moho. The small-wavelength gravity lows and highs south of the CIS coincide with the felsic and the basic volcanics of tholeiitic to calc alkaline-type magmatism. These signatures suggest that the SFB represents a Proterozoic collision zone between the Bundelkhand craton towards the north and the Bhandara craton towards the south, with the CIS as the suture and plausible subduction from the north to the south. A 1000-km long NE-SW gravity profile across the Godavari Proterozoic Belt (GPB) and the Dharwar Craton (DC) also shows a regional gravity high over the GPB; and a regional gravity low over the DC. They are interpreted due to high-density rocks in the upper crust and thickening of crust from 35 km under Eastern Dharwar Craton to 41 km under the Western Dharwar Craton respectively. These signatures along with contractional deformation of the Eastern and the Western GPB indicate that it represents a compressional terrane boundary between the Bhandara craton and the DC.