An ongoing lithospheric dripping process beneath Northeast China and its impact on intraplate volcanism

Abstract

Unique intraplate volcano eruptions and westward volcano migration since the Oligocene are observed in NE China, an overriding continental zone tectonically controlled by the subduction of the northwestern Pacific plate and the opening of Japan Sea. Interestingly, these intraplate magmatic events occur around a subsiding basin (the Songliao Basin), but no volcanic activities have been observed within the Songliao Basin. The geodynamic mechanism responsible for these volcanoes remains unclear. To address the geodynamic process beneath NE China, numerical experiments are conducted constrained by datasets from regional reconstruction, seismic and volcanic studies. Vertical velocity field of mantle convection and lithospheric partial melting structures yielded from our numerical model show mantle upwelling and melting center migrates from the east to the west of NE China with the westward propagation of the stagnant slab, leading to the volcano migration. Also, with the subduction retreat of NW Pacific plate and the opening of the Japan Sea, significant lithospheric thickness differences between Changbaishan-Mudanjiang Region and the Songliao Basin develop, leading to lithospheric unstable dripping. This dripping structure prevents the partial melting of the lithosphere but facilitates the subsidence of the Songliao Basin in central NE China. Moreover,  the lithospheric dripping model successfully predicts upper mantle structures consistent with the proposed tomography model, the observed Moho depth, and surface topography variations. Thus, the lithospheric dripping induced by lithospheric thickness difference and the subduction of the Pacific slab provides a robust mechanism for the unique geodynamic process in NE China.