East Asia mantle tomography: New insight into plate subduction and intraplate volcanism

Abstract

We present a new P-wave tomographic model beneath East Asia by inverting 1,401,797 arrival-time data recorded by the regional seismic networks in East Asia and temporary seismic arrays deployed on the Tibetan Plateau. Our high-resolution tomography shows that the subducted Pacific slab is revealed clearly as a high-velocity (high-V) zone and it becomes stagnant in the mantle transition zone beneath eastern China. Prominent high-V anomalies atop the 410km discontinuity are detected beneath the eastern North China Craton and Northeast China, suggesting that lithospheric delamination may have occurred and greatly affected the thermal state, intraplate magmatism and surface topography of this region. The Indian lithosphere is characterized by a high-V anomaly and it is subducting nearly horizontally beneath the entire or most parts of western Tibet and with a small dipping angle to the southernmost part of eastern Tibet. The intraplate magmatism in different parts of East Asia has different origins. The active Tengchong volcano is underlain by a prominent low-velocity (low-V) anomaly in the shallow mantle, which may be caused by the subduction and dehydration of the Burma microplate plate (or Indian plate). The Hainan volcano is underlain by a plume-like low-V anomaly that extends down to at least 1000km depth and seems to be related to the deep subductions of the Burma microplate (or Indian plate) in the west and the Philippine Sea plate in the east. Prominent low-V anomalies are detected beneath the Changbai, Longgang and Xianjindao volcanoes in Northeast Asia, which may be related to the rollback of the subducting Pacific slab as well as the convective circulation process in the big mantle wedge above the stagnant slab. The origin of the Wudalianchi volcano in Northeast China seems associated with the upwelling of asthenospheric materials caused by the subduction-induced lithospheric delamination.