Crustal Footprint of the Hainan Plume Beneath Southeast China

Abstract

AbstractAlthough global and regional seismic tomography results have revealed the presence of a mantle plume beneath Hainan Island, there is little evidence for a hotspot track associated with the Hainan plume. Here a joint inversion of satellite gravity measurements and seismic surface wave dispersion data was performed, and the results show that a linear corridor of high seismic velocity anomalies beneath the crust is located northeast of Hainan Island beneath the Southeast China. Geodynamic modeling further demonstrates that this corridor could have been formed by the interactions between a mantle plume and the continental lithosphere with a weak lower crust. Volcanic age distributions of sporadic oceanic island basalts suggest that this track was likely formed since the late Cretaceous, which helps to constrain the averaged plate velocity of the South China Block, relative to the Hainan plume, to be ~1.8 cm/year to the northeast since 80 Ma. Our result provides a novel explanation for the crustal thickness variations, related Vs anomalies, and observed oceanic island basalts in this area. It also provides an independent way for constraining plate motion history of the continental lithosphere.