Early arrival of the Réunion plume at the base of the Himalaya?

The Réunion mantle plume is known to have produced the Deccan Traps in west-central India, but its early evolution before the Deccan eruption remains poorly constrained. In this paper, we report a mafic intrusion in the eastern Tethyan Himalaya, the Manla dolerite sill, with a U–Pb zircon age of 68.7 ± 1.0 Ma and Réunion plume-like geochemical features. Similar to other ∼73–68 Ma pre-Deccan rocks scattered across the northern Indian plate, the Manla dolerite likely represents initial melts from the Réunion plume. Considering the widespread Campanian stratigraphic hiatus throughout the Tethyan Himalaya, we propose that these pre-Deccan geological records in the Himalaya area resulted from the Réunion plume evolution process involving upwelling, ponding and rapid spreading along the base of the northern Indian plate during 80–70 Ma. Major and trace element modeling results show that the Manla rocks, like the largest Western Ghats sequence in the Deccan area, have low melting pressure, suggesting that they formed in preexisting thin areas. Combined with lithosphere thickness variations in the Indian plate, the thick northern Indian plate may have been the key factor inhibiting massive melt production when the Réunion plume head first impinged on it, and the large Deccan eruption was triggered when the thin central-western Indian plate moved over the Réunion plume. The early arrival of the Réunion plume head coincides with the unusual acceleration of the Indian plate starting at ∼75–70 Ma and suggests a prolonged plume - Indian plate interaction period. Our reconstructions suggest that plume heads can impact several million years ahead of large igneous provinces formation and can affect the movements of the overlying plate in an incubation way.