Teleseismic imaging results reveal Proto-South China Sea subduction remnants

The subduction and disappearance process of the Proto-South China Sea is closely related to the opening of the South China Sea. Studying its subduction process and dynamic mechanism helps to explore the Cenozoic evolution model of the South China Sea. We collected teleseismic travel time data from Southeast Asia over the past 20 years, preprocessed the original data through data filtering, picking first arrival , and crustal correction, and obtained a three-dimensional velocity model of Southeast Asia using the Fast Marching Teleseismic Tomography(FMTT) method. The velocity imaging results reveal the presence of high-velocity anomalies in the mantle and mantle transition zones beneath Borneo and the Philippines. It is worth noting that the distribution range of serpentinite and serpentinite belt discovered in this area is highly consistent with the range of high-velocity anomaly bodies. Therefore, it is highly likely that the high-velocity anomalous bodies discovered in this area are remnants of the Proto-South China Sea subduction plate in the mantle transition zone. The morphology of residual subduction plates indicates that the Proto-South China Sea was subducted and closed from south to north, which may have had a certain impact on the Cenozoic seafloor spreading of the South China Sea; The detailed distribution range of residual plates further delineates the location of the disappearance of the Proto-South China Sea.