Isostasy and crustal structure of the Chagos–Laccadive Ridge, Western Indian Ocean: Geodynamic implications

Abstract

The Chagos–Laccadive Ridge (CLR), a prominent linear aseismic ridge in the Western Indian Ocean is believed to be a trace of the Réunion hotspot. In order to understand the mode of emplacement of this ridge and the nature of the underlying crust, we carried out three-dimensional (3D) flexural modelling and coherence analysis of satellite-derived gravity and bathymetry data along the ridge. The analysis revealed variations in Effective Elastic Thickness ( $$T_{\mathrm{e}}$$ ) along the CLR. While the northernmost part of CLR is associated with low $$T_{\mathrm{e}}$$ of 3 km with a subsurface to surface loading ratio (f) of 1, towards the south, the Maldive Ridge and the Chagos Bank have a fairly uniform $$T_{\mathrm{e}}$$ of 8–10 km with a very low loading ratio f of 0.1–0.2. We consider the Laccadive Ridge as a continental sliver possessing underplated magmatic rocks caused by the Réunion hotspot volcanism. The Maldive Ridge and the Chagos Bank appear to have emplaced on a lithosphere of intermediate strength possibly on the flanks of the Central Indian Ridge.