Tracking the source heterogeneities and distinct origins of flood basalt provinces: Insights from Panjal, Rajmahal-Sylhet and Deccan Traps

The Panjal, Rajmahal–Sylhet, and Deccan Traps in India constitute voluminous flood basalt provinces emplaced under distinct tectono-magmatic regimes. The formation of Panjal Traps (∼289 Ma) is attributed to extensional tectonic processes—specifically lithospheric thinning and decompression melting of the lithospheric mantle domains associated with rifting of the Cimmerian terranes and opening of the Neo-Tethys Ocean, whereas the Rajmahal–Sylhet (∼117 Ma) and Deccan (∼66 Ma) Traps are considered to represent mantle plume-related large igneous provinces (LIPs) associated with the Kerguelen and Réunion hotspots, respectively. Using the most primitive basalt compositions, we constrained mantle potential temperatures (T _p), source lithologies, and melting depths of these spatially and temporally distinct provinces. The Panjal basalts yield T _p of 1379–1470 °C, with onset of melting at ∼81 km depth. The Rajmahal–Sylhet and Deccan basalts exhibit elevated T _p (1545–1639 °C and 1519–1556 °C), with melting initiated at depths of ∼177 km (Rajmahal–Sylhet) and ∼ 132 km (Deccan), respectively. Peridotite versus pyroxenite melting models suggest that plume-derived LIPs are best explained by the melting of hydrous peridotite sources. Pyroxenites are likely restricted to lithospheric mantle domains and are not intrinsic to deep mantle plume sources. The rapid increase in root mean square (RMS) plate velocities of India during the post-Pangean period are correlated with the spatio-temporally associated Mesozoic LIP events. This suggests that mantle plumes likely played a key role in accelerating India's motion by enhancing the influence of far-field plate boundary forces, possibly through thermomechanical erosion of the cratonic keel beneath the Indian plate.