Mapping the Mantle on the Marion Rise

The global ridge system is dominated by ocean rises where they shoal to shallow depth depth near mantle hotspots. The classic case is the Icelandic Rise, which, like most such rises is generally believed supported by a hot deep mantle plume and thick crust. The Marion Rise on the SW Indian Ridge, is nearly the same size: though a kilometer deeper it is 1000-km longer. While closely associated with a hotspot track originating at the Madagascar Plateau and terminating near Marion Island, Zhou and Dick, 2013 suggested the Rise is supported by buoyant depleted mantle not a mantle plume associated with the Marion Hotspot. Instead the plateau represents the initial burst of melting of delaminated subducted crust and sediment in the upper mantle with Gondwana breakup, followed by melting of the vestigial remains of this material to produce the hotspot track. RV Thomas Thompson Cruise TN365 in February and …