Density inhomogeneities beneath Deccan Volcanic Province, India as derived from gravity data

Abstract

New gravity measurements at close spacing (1–2 km) along three profiles (∼550 km each), starting from west coast of India upto the eastern margin of the Deccan Volcanic Province (DVP), are carried out to understand the subsurface density structures and tectonics of the region. The computed density model, constrained with seismic and other geophysical information, delineates high-density (3.1 g/cm3) underplated lower crust and low density (3.2 g/cm3) upper mantle along the west coast of India, which may be attributed to the interaction of the Reunion hot spot with the Indian lithosphere and rifting along the west coast of India. Analysis and modelling of the gravity data also suggest different sources for two large wave length gravity ‘lows’, namely the “Koyna low” and the “Kurduwadi low”, observed over the DVP. The “Koyna low” is caused mainly by isostatic compensation, manifested as crustal thickening upto 40 km with low density (3.2 g/cm3) upper mantle, while the source of the “Kurduwadi low” appears to be shallow and is mainly attributed to the emplacement of low-density material, such as granitic bodies along fractures/shear zones.