Historical Interaction of Central Indian Ridge and Réunion hotspot in the Indian Ocean

The interaction between the Central Indian Ridge (CIR) and the Réunion hotspot has significantly influenced the formation of notable volcanic features in the Indian Ocean over the past 60 million years, including the Maldive ridge and Chagos bank on the Indian-Australian Plate, as well as the Mascarene Plateau, Mauritius Island, Réunion Island, and Rodrigues Ridge on the African Plate. Plate reconstruction results indicate that the distances between the CIR and Réunion hotspot have varied throughout the geological history, transitioning from off-axis (65-40 Ma) to on-axis (40-20 Ma) and back to off-axis (20-10 Ma) cases, with the current distance exceeding 1,000 km. This makes the CIR-Réunion system an ideal setting for studying both on-axis, off-axis interactions and their transitions. In this study, we utilized the advanced computational geodynamic platform ASPECT to investigate the CIR-Réunion system, focusing on 3-D mantle evolution, deep structures and their connectivity, and the migration pattern of hotspot material towards the ridge and surrounding regions. Our results illustrate the dynamic processes of mantle and crust, the dispersion of temperature anomaly, and the migration of plume material. The model results show that the critical points of the interactions begin and cease are ~50 and ~10 Ma, respectively. There is no direct connection between the ridge and hotspot at present. These indicate that the traces of the ridge-hotspot interaction may show spatial features, but it actually reflects the temporal variations.