Thermal Modeling of the Tectonic Evolution of the Southwest Subbasin in the South China Sea

Abstract

The rifting and seafloor spreading of Southwest subbasin of South China Sea is the most important tectonic event in the forming process of South China Sea from the late Cretaceous period to Middle Eocene. We simulate the thermal evolution process of this region with 3-D finite element method and research the rifting deformation of Southwest subbasin, the duration of seafloor spreading, the rising of mantle materials, the crush and spreading energy of the lithosphere dyke along the spreading center, and the magmatism by computing the deformation and temperature structure. The result indicates that the extension duration of the sea basin is 10 to 15Ma. Because of insufficient deep dynamics condition, the rising of mantle materials stopped gradually and the lithosphere lost the extension drive, and then the spreading center became a dead rift valley with a leftover spreading center but not ridge or central uplift belt. Though the rising potential of the mantle materials in this area is insufficient, there are quite violent magma spewing activities leading to the growing up of seamount after the molding of the sea basin in the region with the partial rifting, especially the extension and detachment of the boundary between basin and margin.