Local slab penetration into lower mantle controls deep-focus seismicity and Changbaishan volcanism in northeast China

Intraplate volcanism in the Changbaishan region of northeast China is underlain by a deep subduction-related earthquake cluster in the mantle transition zone, but the underlying physical connections between them remain elusive. Here we use teleseismic double-difference tomography to obtain high-resolution images of the subducting Pacific slab to provide better constraints on slab morphology and potential relationships with volcanism and deep-focus seismicity. Our results reveal a narrow slab tongue penetrating the lower mantle, flanked to the north and south by slab stagnating in the mantle transition zone. This geometry creates a gap for sub-slab hot materials to ascend, providing a deep mantle source for Changbaishan volcanism. Additionally, the slab tongue is warped, which spatially coincides with a cluster of deep earthquakes, implying that an active deformation zone causes the clustered deep earthquakes. Our findings demonstrate that Changbaishan volcanism and deep-focus earthquakes are fundamentally controlled by the subducting slab's dynamic morphology beneath northeast China.