Interactions between hotspots and the Southwest Indian Ridge during the last 90 Ma:Implications on the formation of oceanic plateaus and intra-plate seamounts

This study investigates the relationship between the hotspot-ridge interaction and the formation of oceanic plateaus and seamounts in the Southwest Indian Ocean.We first calculated the relative distance between the Southwest Indian Ridge (SWIR) and relevant hotspots on the basis of models of plate reconstruction,and then calculated the corresponding excess magmatic anomalies of the hotspots on the basis of residual bathymetry and Airy isostasy.The results reveal that the activities of the Marion hotspot can be divided into three main phases:interaction with the paleo-Rodrigues triple junction (73.6-68.5 Ma),interaction with the SWIR (68.5-42.7 Ma),and intra-plate volcanism (42.7-0 Ma).These three phases correspond to the formation of the eastern,central,and western parts of the Del Cano Rise,respectively.The magnitude and apparent periodicity of the magmatic volume flux of the Marion hotspot appear to be dominated by the hotspot-ridge distance.The periodicity of the Marion hotspot is about 25 Ma,which is much longer than that of the Hawaii and Iceland hotspots (about 15 Ma).