Seamount volcanism associated with Earth’s basal mantle structures

Abstract While seafloor spreading and subduction can explain much of Earth’s volcanism, magmatism oc-curring within plate interiors requires a deeper mantle explanation. Indeed, several types of in-traplate volcanism, such as active hotspots, large igneous provinces, and kimberlites, have been tectonically-reconstructed to the margins of two continent-sized structures (termed the large low shear velocity provinces, LLSVPs) in the deepest mantle beneath Africa and the Pacific. Here we show that thousands of seamounts, small seafloor volcanoes with unknown age, are also linked to the LLSVPs. Using a new seamount catalog, we show that seamounts are more voluminous on seafloor that has passed above the margins of the LLSVPs. This volcanic enhancement is domi-nated by the Pacific basin, where LLSVP-associated seamount volumes are amplified by a factor of two even if seamounts associated with known hotspot tracks are excluded. The stronger associ-ation of seamounts with the Pacific LLSVP may be due to hemispheric differences in mantle tem-perature, transition zone hydration, and/or mantle flow vigor between the Pacific and African sides of the planet. This discovery provides support for the hypothesis that multiple forms of intraplate volcanism, now including seamounts located outside of known plume tracks, are associated with heat rising from the LLSVP margins.