Integrated geophysical research on the tectonic attribute of conjugate continental margin of South China Sea

In this paper, the density and magnetic structure of six profiles in South China Sea was inversed based on the latest potential field data and the rock physical property analysis. The constraint information from the ocean bottom seismometer (OBS) data and multi-channel seismic (MCS) results was used in the inversion process. And the FF' profile used the latest MCS data colleted in 2009 by the 973 project. Based on the MCS data, the interval velocity is computed and the structure model is used for the gravity modeling. Based on the deep structure analysis and the density/magnetic structure of the six profiles in this paper, the tectonic attribution of the northern and the southern margins of the South China Sea are more like non-volcanic continental margin. There exists high density layer in the lower crust accompanied with active magma activity to the east of CC' profile in north margin of SCS. But it is lack of the seaward dipping reflectors in this region. So we deduce that the high density layer in lower crust is the result of splitting of the continental margin after the sea floor spreading, which is same as the magmatic rocks in shallow layer. The magnetic basement and the deep structure of the Zhongsha Uplift and Liyue basin are quiet similar. It was deduced that they were the same block before the pull of sea basin. They are a pair of conjugate points of the northern and southern margins of the South China Sea. The integrated geophysical interpretation of southern margin of southwest sub-sea basin indicated that the Mesozoic group can be found near the base of slope but they may be not continuous.