Inference of a plume conduit beneath the Réunion Island from 3D migration of Ps conversions from the mantle transition zone.

The Réunion hotspot is the best example of a primary plume, manifested as intraplate-volcanism, a large igneous province and a geochemical anomaly. In this study, we investigate the mantle transition zone (MTZ) structure beneath the Réunion Island using 3D-migration of P-Receiver functions, to decipher the effect of the plume on the MTZ and its architecture. Results indicate a thin MTZ in the regions surrounding the Réunion, like Madagascar and its vicinity, eastern and south-eastern sides of the Réunion, suggesting high-temperature anomalies within, caused by the plume. Interestingly, we detect a depressed 410 km discontinuity exactly beneath the Réunion hotspot and a broader depression of 660 km discontinuity within and regions in its proximity. These maiden results shed-light on the high-temperature anomalies in the mid-mantle, probably sourced from the Réunion plume and provide evidence for the Majorite-garnet phase transformation at 660 km discontinuity. We postulate that an ascending Réunion plume has initially hit the 660 km discontinuity, got horizontally spread and further progressed to the 410 km discontinuity as a columnar structure.