La réunion: An example of channeled hot spot plume

La Réunion, a large intraplate volcanic system in the Mascarene Basin (Indian Ocean), is widely considered as the expression of a mantle plume or hotspot. It lies in a region of the Mascarene Basin bounded by 2 major transform faults and an extinct rift. The bathymetry suggests the presence of a positive topographic anomaly around La Réunion. We have compared the bathymetry with a theoretical bathymetry based on the thermal subsidence of the oceanic lithosphere as a function of its age. A bathymetric anomaly of several hundreds of meters is shown, but it is confined to the La Réunion zone. Analogue models have been carried out to explore the deformation resulting from a mantle plume rising beneath a faulted lithosphere. They show that the plume and the associated deformation are channeled into the area enclosed by the transform faults and the paleo-rift. The deformation is virtually nil outside the zone fault-bounded zone. We have analyzed the surface features and the available gravity and magnetic data in order to find evidence of the deformation predicted by the presence of the bathymetric anomaly and by the analogue models. No clear pattern of deformation has been recognized, but we demonstrate the complex organization of the oceanic crust in the La Réunion zone. The fact that the plume head focuses on the restricted area of the zone may amplify the dynamic support of the lithosphere beneath La Réunion where not flexure is observed. We also suspect that some seamounts near La Réunion could correspond to a recent magmatic activity distinct from that of the island. The mantle plume-lithosphere interaction model presented here is a new to the oceanic domain and it will have to be confirmed by subsequent observations in the La Réunion area and possibly in other similar sites on Earth.