Crust beneath the northwestern Deccan Volcanic Province, India: Evidence for uplift and magmatic underplating

Abstract

The northwestern Deccan Volcanic Province of India and its pericratonic rift basins were reactivated during different stages after the breakup of India from the Gondwanaland and collision with the Asian plate. In this study, we present results of crustal thickness and average crustal V p /V s ratios beneath this plume-affected region using common conversion point imaging and H-k stacking analysis of 6893 receiver functions using data from a network comprising 58 broadband seismic stations sited on diverse tectonic terrains. We find large variations in crustal thickness, with the Moho depths varying from 28 to 43 km in the Kachchh rift, 28 to 38 km in the Cambay rift, 39.5-41.5 km in the north and eastern parts of the Cambay rift, and 29 to 39 km in the Saurashtra region and South Gujarat. A Moho upwarp of 6 to 7 km in the Saurashtra region can be attributed to positive buoyancy and uplift due to thermal influx affected by the Reunion plume. High crustal V p /V s ratios beneath the Kachchh rift (1.8 to 2.05), coastal areas of Saurashtra (1.75 to 2.06), and North Gujarat (1.81 to 1.85) indicate dominance of a mafic/ultramafic crust. High regional heat flow, high electrical conductivity, large intracrustal S wave velocity reduction, and high average crustal Poisson's ratios are consistent with partial melt related to the process of magmatic underplating in the lower crust. At other stations, the crust appears to be felsic with V p /V s ratios in the range of 1.57 to 1.76.

Crustal Structure Beneath India and Tibet: New Constraints From Inversion of Receiver Functions

“…We prepared an updated crustal thickness map using published results from controlled source seismics and RFs (Singh et al, ). The crustal thickness estimates from the present study are complemented with those from recent publications (Western Tibet, Zhang et al, ; Gilligan et al, ; Bengal Basin, Singh et al, ; Southern Granulites, Sharma et al, ; western DVP, Chopra et al, ; K. M. Rao et al, ; Singbhum, Mandal & Biswas, ), for completeness. The final map produced still has data gaps from central India and parts of northern Tibet (Figure ).…”

“…Structural variations across major rift zones like Godavari, NSL, and Cambay are distinct from their surroundings (Figures and ). The updated crustal thickness map produced in this study documents a thinner crust (28–33 km, K. M. Rao et al, ) beneath the Cambay Rift separating the northwestern and southwestern portions of the Deccan volcanic province. The Godavari and Narmada rifts show a thicker crust with evidence for magmatic underplating as revealed by the high shear velocities in the lower crust (supporting information Table S1) and a diffused Moho beneath these rift zones (Kumar et al, ; Singh et al, ).…”

Seismic Imprints of Plume‐Lithosphere Interaction Beneath the Northwestern Deccan Volcanic Province

“…Since the amplitude of the surface wave decreases exponentially with depth, resolution of the fundamental mode surface wave tomography is more accurate in the first 300 km of the upper mantle (Bodin et al, ). Previously, many seismic studies have been attempted to understand the lithospheric structure beneath the DVP (e.g., Kaila et al, , ; Mandal, ; Maurya et al, ; Rao et al, ; Tewari et al, ). Most of them are restricted to investigation of crustal structure using receiver functions or shallow structure for oil exploration using deep seismic sounding (DSS) data.…”

Geoelectric structure of northern Cambay rift basin from magnetotelluric data

“…Plume interaction signatures have been traced through the Cambay basin to the immediate east of the Saurashtra peninsula (Campbell and Griffiths 1990). Rao et al (2015) analyzed near-surface shear velocities (NSV) using a network of permanent broadband stations over northwestern DVP. The Cambay basin region shows very small NSV values of 1.03-2.25 km/s, indicating the presence of sediments within the rift basin.…”