Mantle discontinuities beneath the Deccan volcanic province

Mantle discontinuities beneath the Deccan volcanic province (DVP) are imaged using about 900 seismograms from a network of six broadband stations deployed in the DVP along a 350 km long north-south profile, paralleling the west coast of India. Teleseismic receiver function analysis of the data enabled distinct identification of the Moho, 410 and 660 km discontinuities. Presence of sub-Moho low velocity zones with velocity reductions in the range of 0.1-0.4 km/s have been brought out through modeling of receiver function stacks at individual stations. The arrival times of P410s and P660s are normal, as predicted by the IASP91 model, and the mantle transition zone thickness is 252 km, which is close to the global average. This study reveals that the upper mantle beneath DVP, south of the Narmada rift does not exhibit any anomalous signatures associated with a mantle plume. A shield-like lithosphere, coupled with the presence of an upper mantle low velocity zone confined to shallow depths beneath DVP, imposes constraints on the mechanisms feasible for Deccan volcanism. The present study does not favour the plume impact/plume incubation models, instead necessitates searching for clues offshore west coast of India and exploring alternate mechanisms.