Interaction of Kerguelen and Amsterdam-St. Paul dual hotspots with Southeast Indian Ridge

Abstract

We investigated the influence of the Kerguelen (K) and Amsterdam-St. Paul (ASP) dual hotspots on mantle evolution and crustal accretion in the eastern Indian Ocean. Using surface plate motion constraints from the global plate reconstruction model and the 3-D mantle convection code (ASPECT), we illustrated detailed processes of mantle upwelling, melting, and crustal accretion in the ridge-dual hotspot system. Model results demonstrate that the K hotspot significantly increased the mantle temperature over a wide region of over 1,500 km, leading to a 1–2 km increase in average crustal thickness along the entire Southeast Indian Ridge (SEIR). Only ridge-dual hotspot interaction models can explain key crustal variations along the SEIR. Gravity analysis revealed the K hotspot's long-term interaction with nearby ridges formed significant crustal anomalies, while the ASP hotspot's 10 Myr interaction with SEIR created localized anomalies. The distance between the ridge and hotspot, as well as plume flux, are key factors controlling the strength of ridge-hotspot interaction. The K hotspot, with its relatively higher plume flux, has double the influence distance of the ASP hotspot. Furthermore, our models indicate a possible direct interaction between the K and ASP hotspots, resulting in the ASP plume materials flowing towards the K plume.