Mantle transition zone dynamics beneath the Northwestern Deccan Volcanic Province, India: Implications for plume mediated upper mantle processes

Abstract

The Deccan Volcanic Province (DVP), formed ∼65 Ma during India's northward drift and linked to the Réunion plume, reveals complex upper-mantle structures. This study uses P receiver function (RF) analysis from 76 broadband stations in Gujarat, Western India, to image upper-mantle discontinuities (d410 and d660) beneath the north-western DVP. RF depth migration was performed using 1-D and 3-D tomographic velocity models—GYPSUM, LLNL-G3Dv3, MEAN2, and a combined regional model (up to 300 km depth) incorporating LLNL-G3Dv3. The estimated mantle transition zone (MTZ) thickness varies from 233 to 248 km in Kachchh, Saurashtra, Cambay, South Gujarat, and the Arabian Sea, while in North Gujarat and the Narmada rift zones; it ranges from 251 to 255 km. The d410 discontinuity exhibits a uniform depression (410–430 km), whereas the d660 remains normal to slightly deepened (650–675 km). The eastern North Gujarat, Narmada zone, and parts of Kachchh exhibit a shallow 410 km and depressed 660 km discontinuity, indicating MTZ thickening. The Cambay thermal anomaly, bounded by these colder regions, likely reflects localized small-scale upwelling coupled with the downwelling of ancient subducted slab remnants. Additionally, 520 km discontinuity was detected, with amplitude peaks suggesting a low-velocity layer above d410. The Mean excess temperatures associated with d410 and d660depressions are ∼150 K and ∼ 323 K, respectively. MTZ structure, thermal anomalies, and mantle velocity heterogeneities collectively indicate plume–lithosphere interaction influenced by relic slab dynamics in the genesis of Deccan volcanism.