Evidence for an upwelling mantle plume beneath the Songliao Basin, Northeast China

A mushroom-like low-velocity body (MLLVB) was defined by tomography beneath Northeast China, which may be linked to a vestige of the Mesozoic upwelling mantle plume. However, multiple lines of evidence indicate that the necessary condition of the upwelling is that the upwelling mantle plume has a temperature sufficiently higher than that of the surrounding mantle. The upwelling mantle plume cannot be defined only based on the low-velocity structure. To investigate this issue, I conducted common conversion point (CCP) stacking of receiver functions in Northeast China and designed six CCP stacking profiles crossing Northeast China. The results show that when the CCP stacking profiles cross the location of the MLLVB, the topography of the 410 and 660 km discontinuities did not exhibit obvious variations; instead, two 520 km discontinuities merged into a single discontinuity, which indicates that the MLLVB had an upwelling temperature condition. The CCP stacking image of the receiver functions also reveals a deepening of the 410 km discontinuity and shallowing of the 660 km discontinuity at the center of the Songliao Basin along the 45 degrees N profiles, which might be associated with the Mesozoic upwelling mantle plume.