Mantle plume – mid ocean ridge interactions revealed from hotspot melt production rate along the Walvis Ridge-Rio Grande Rise

Abstract

Mantle plume and mid-ocean ridge (MOR) interactions have a profound impact on geological processes, such as large igneous province eruptions, mid-ocean ridge jumps and plume flow towards the MOR. The Walvis Ridge and Rio Grande Rise provide an excellent opportunity to study these interactions, as they have a record of during- and post-interaction stages. We have estimated the hotspot melt production rate along the Walvis Ridge - Rio Grande Rise. Our findings are as follows: (1) The hotspot melt production rate during plume-MOR interaction is seven times higher than that after the interaction, primarily because a thinner lithospheric coverage over the plume allows for greater decompression melting and facilitates the ascent of melt through the lithospheric mantle to accrete to the crust. (2) The waning of the Tristan-Gough plume is indicated by a decreasing melt production rate and an increase in inter-volcano spacing. (3) The linear ridges on the western side of the Guyot Province likely result from mantle plume flow beneath the lithosphere from the hotspot to the Mid-Atlantic Ridge. (4) Fracture zones enhance hotspot melt production rates.