Numerical simulation of subduction-induced molten plume: Destruction of overriding plate and its dynamic topographic responses

In the process of oceanic crust subduction, with the increase in temperature and pressure and the difference in density, the subduction-induced molten plume will rise rapidly and act on the lithospheric mantle bottom of the overriding plate, which may lead to the decrease in the lithospheric damage and the drastic change of surface morphology. This process is similar to the destruction of the lithosphere caused by mantle plume. So far, there have been little studies on the formation of subduction-induced molten plumes and their damage to the lithosphere, especially on the responses of surface dynamic topographic changes to the deep destruction. Based on the conservation equations of matter, momentum and energy, the I2VIS finite difference method is adopted by the authors to calculate and reveal the partial melting of the subducted oceanic crust at different times and depths under given material parameters and boundary conditions. The process of forming a subduction-induced molten plume is obtained, and then the process of molten plume-lithosphere interactions is further simulated, and the response of shallow topographic changes are analyzed. The numerical simulation results show that in the process of oceanic plate subduction, the composite molten plumes formed by subducted terrigenous sediment and oceanic crust eroded the bottom of the lithosphere longitudinally, and resulted in lithospheric thinning. During the transverse erosion of the molten plumes, the melting range of the lithospheric mantle increases up to 300 km. In terms of geomorphic change, plate subduction results in compression deformation of the continental front, which may reach 300 km. At the same time, the erosion of the molten plumes associated with subduction to the bottom of the lithospheric mantle is gradually strengthened, and the dynamic topographic changes increased, while uplifting continued, and ultimately reached a figure of 4 km. The variation range of dynamic topography is limited to 300 km, which is consistent with the damage range of lithospheric mantle.