Model of lithospheric rifting controlled by magmatic underplating in the South China Sea

Abstract:

South China Sea is one of the largest basins in the western Pacific marginal sea, which is located in the intersection area of the Eurasia, the India-Australian and the Pacific-Philippines plate. As the tectonic movement was controlled by three different plates, South China Sea basin has the colorful geological phenomenons and complex structure. From the point of its structural development history, South China Sea has its own unique development model, which is formed by the continent rifting and expansion, while the tectonic evolution has close relationship with geological peripheral units. According to the seismic detection and magnetic integrated geophysics, the studies found that high-speed lower crust layers are widespread in the northern South China Sea and the northeast of continental margin, these layers are mainly located in continental slopes and some high-degree tensional continental shelves. Researches suggested that materials of high-speed in lower crustal layers are formed by the bottom magmatic underplating rather than serpentinized mantle peridotite. These layers are formed in Cenozoic and has close relationship with extension. This study established a two-dimensional thermal - mechanical coupled finite element model to simulate the role of underplated magmatic bodies in the localization of deformation. Studies show that the deformation can be redistributed into a different region if the underplated magmatic bodies emplacement in multiple regions during the extensional process. Based on the numerical model behaviour in this study, we have discussed the microcontinent formations observed in the South China Sea.