On the relationship between volcanic hotspot locations, the reconstructed eruption sites of large igneous provinces and deep mantle seismic structure

Abstract

It has been proposed that volcanic hotspots and the reconstructed eruption sites of large igneous provinces (LIPs) are preferentially located above the margins of two deep mantle large low shear-wave velocity provinces (LLSVPs), beneath the African continent and the Pacific Ocean. This spatial correlation has been interpreted to imply that LLSVPs represent long-lived, dense, stable thermo-chemical piles, which preferentially trigger mantle plumes at their edges and exert a strong influence on lower-mantle dynamics. Here, we re-analyse this spatial correlation, demonstrating that it is not global: it is strong for the African LLSVP, but weak for the Pacific. Moreover, Monte Carlo based statistical analyses indicate that the observed distribution of African and Pacific hotspots/reconstructed LIPs is consistent with the hypothesis that they are drawn from a sample that is uniformly distributed across the entire areal extent of each LLSVP: the stronger spatial correlation with the margin of the African LLSVP is expected as a simple consequence of its elongated geometry, where more than 75% of the LLSVP interior lies within 10° of its margin. Our results imply that the geographical distribution of hotspots and reconstructed LIPs does not indicate the extent to which chemical heterogeneity influences lower-mantle dynamics.