3-D Structure and geodynamic evolution of accreted igneous layer in the Narmada-Tapti region (India)

Abstract

The Narmada-Tapti rift system is an unusual feature crossing the west coast of India. A recent 2-D analysis of Bouguer gravity anomaly combined with four deep seismic sounding profiles in the region has revealed a 15–20 km thick high-density (3.02 g cm −3) accreted igneous layer at the base of the crust. For a more realistic approximation a 3-D density model of the proposed underplated layer is obtained. The thickness of the lower crustal accreted igneous layer varies from 8 km beneath the eastern part to about 16 km beneath the central part and about 24 km beneath Navsari in the westernmost part of the region. The greater thickness of the magmatic body beneath the Navsari gravity high presents itself as one of the potential feeder channels for the Deccan flood basalts. The study further deciphers a normal Moho located at a depth of about 38 km in the southwestern part of the region. The geothermal signatures show an upwarped asthenosphere indicating the existence of partial melting conditions at very shallow depths. It is suggested that the massive eruption of the Deccan flood basalt on the west coast of India has modified the deep crustal structure of the Narmada-Tapti region in agreement with rheological boundary conditions.