Seismological Evidence for Crustal Thinning and Melting Beneath the Leiqiong Volcanic Area, South China: Implications for Plume-Lithosphere Interaction at a Passive Continental Margin

Both mantle plumes and passive margin extension have been recognized as crucial mechanisms governing intracontinental volcanism and lithospheric evolution. However, the synergistic interactions between these two processes in modulating lithospheric modification remain poorly constrained. The Leiqiong volcanic area (LQV), on the northern continental margin of the South China Sea, has witnessed intense volcanic activity since the late Cenozoic. Though geophysical imaging show mantle plume beneath LQV, limited resolution hinders our understanding of lithospheric modification and magmatic processes. In this study, analysis of teleseismic waveforms from newly deployed broadband stations reveals the lithospheric thinning to the south of LQV, crustal thinning, high stretching factors, high Vp/Vs ratios and crustal melting within LQV. In comparison with global hotspots modulating lithospheric architecture and melting, our results offer seismological evidence that passive margin dynamics rival mantle plumes in lithospheric modification, highlighting a plume-lithosphere interaction that jointly drives volcanism and continental margin destabilization through multi-mechanisms.