Low-velocity anomaly in the Coral Sea associated with subducting slabs and the Woodlark rift

Classical plume models offer insights into intraplate volcanism and seamount chain formation by assuming a cylindrical upwelling of hot materials from the core-mantle boundary. The interaction of mantle plumes with ridges or subducting slabs disrupts typical plate tectonics, leading to distinctive tectonic phenomena such as ridge jumps or slab stagnation. However, thermal plume models sometimes fall short in explaining perplexing tectonic features, necessitating consideration of compositional heterogeneities within mantle plumes. Here, using multimode waveform tomography, we identify a large, vertically divergent low-velocity anomaly in the upper mantle beneath the Coral Sea in the southwestern Pacific, which circumvents the remnants of subducting slabs toward northeastern Australia with intraplate volcanism, and the Woodlark rift, the most rapidly extending continental rift. Our findings furnish seismic evidence for the widespread propagation of a thermochemical mantle plume spanning over 10° at depths of 270–410 km, facilitating its simultaneous contacts with slabs and rifts.