The melt content of the low velocity layer in the eastern South China: Implications for the subduction process of the Western Pacific plate

The low-velocity layer (LVL) atop the mantle transition zone involves diapiric segregating, melt upwelling, mantle mixing, magmatic eruption and the remnants. The lateral variations of the LVL could record the process of the subducting plates. The LVL beneath the eastern South China intensively affected by the subduction of Western Pacific plate since Mesozoic is imaged with observed P-wave triplications recorded by the dense Chinese Digital Seismic Network. The thicknesses of the LVL are 57 km for sub-region A, 40 km for sub-region B, and 20 km for sub-region C. The melt fractions related to the different velocity structures of the LVL beneath three north-to-south adjacent sub-regions A, B and C of the eastern South China are estimated with the bulk solid compositions, reference potential temperatures, compositions and dihedral angles. The spatial characteristics of the melt fractions and the LVL thicknesses are in accord with the recession directions of the subduction fronts of the Western Pacific plate. This consistency provides a powerful information for understanding the plate subduction process. •The LVL atop MTZ beneath the eastern South China is affected by the subduction of Western Pacific plate since Mesozoic.•The melt fractions are estimated by using the bulk solid composition, potential temperature, composition and dihedral angle.•The spatial characteristics of the melt fractions are agree with the recession direction of Western Pacific plate subduction.