Figure - available from: Journal of Geophysical Research: Solid Earth
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(a) Evolution of a thermochemical plume in the 3D reference model (buoyancy number: B = 0.8, viscosity ratio: μ = 100 and heat producing element concentration (cHPE) same as the background mantle): (i) Piling up of TBL due to forcing by a downwelling flow in mantle, leading to initiation of an instability on the extreme right side of the TBL, followed by lateral advection and climb of the instability to the pile crest, (ii) Development of a mature plume from the instability, (iii) Perturbation of the plume head at the mid‐mantle transition zone to produce a primary pulse. Note that the pulse in the upper mantle undergoes deflection to the right under the influence of plate velocity, and (iv) Sequential formation of multiple pulses with time by mid‐mantle perturbation. (b) Pulsating ascent dynamics of a thermochemical plume at the mid‐mantle transition zone: Development of successive four pulses (i–iv) from the thermochemical plume. Colors (Crameri et al., 2020) represent the temperature and dashed yellow lines delineate the pile margin. Insets show the dynamic topography (in km) corresponding to each pulse in the panels. The horizontal dimension of the insets correspond to 5,000 km around the location of the pulse.
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Mantle plumes, originated in deep Earth’s interior are thought to be a major source of enormous magma supply required for the formation of large igneous provinces (LIPs). This article focuses on the pulsating nature of Deccan volcanism in peninsular India, which is a remarkable LIP event at the end of the Cretaceous Period in...
Citations
... The primary 206 landform of this rift valley is the Cretaceous peneplain, which was rifted and subsequently 207 buried by extensive lava flows. Shear Velocity Province (LLSVP) (Ghosh et al., 2024). Glišović and Forte (2017) other hotspots, such as Iceland and Tristan da Cunha, the Réunion hotspot is located at the edge 241 of the African LLSVP, suggesting that the LLSVP may have acted as a primary feeder for the 242 plume, at least during the Cenozoic (Petersen et al., 2016;Zhao, 2015). ...
... Furthermore, recent geodynamic models indicate that plume activity occurred episodically, 246 controlled by its interactions with the 660-km transition zone (Ghosh et al., 2024). ...
Indian craton comprises a number of old rifts, e.g., the Narmada, the Mahanadi and the Godavari rifts, which reactivated in multiple stages during the supercontinent breakup events. The latest reactivation of the Indian rift system occurred at the Cretaceous-Tertiary boundary when the Réunion plume interacted with the Indian plate, leading to the massive Deccan volcanism at 66 Ma. Although the plume-driven rift tectonics has been a subject of lively research over past decades, how a pre-existing rift system can modulate the plume dynamics, particularly in continental settings, remains inadequately explored. This study addresses this problem in the context of the Réunion plume encountering the Indian lithosphere. We develop 2D thermomechanical models to simulate plume-rift interactions, systematically investigating the modes of interactions as a function of plate velocity (Vp) and plume–rift (δ) distance. Our numerical experiments reveal that small δ (< 250 km) or high Vp (> 1cm/year) conditions redirect a large portion of the plume material towards the pre-existing rift, resulting in significant underplating and subsequent melting beneath the rift undergoing reactivation. Increasing δ or lowering of Vp weakens the plume-rift interaction, leaving the pre-existing rift zone almost passive, where the underplated plume materials stagnate beneath the lithosphere with little melting. The model results suggest that the Narmada rift, which was closer to the Réunion plume, caused significant deflection of the plume and its melting with Moho upwraping. In contrast, the Godavari rift, located at a larger distance from the plume, behaved passively, allowing underplating of the plume at the lithospheric base with no significant melting and Moho downwraping, as supported by geophysical observations. Finally, this study provides a new insight into the differential responses of the Indian rift system during the Reunion plume event.
