There are two types of volcanic rocks in the South China Sea (SCS):the mid-ocean ridge basalts (MORB) and the ocean island basalts (OIB). The International Ocean Discovery Program (IODP) Expeditions 349, 367, 368 and 368x have successfully drilled out the basement of the SCS basin, for the first time, with samples of the oceanic crust during the initial opening (~34 Ma) and the final spreading (~15-16 Ma) of the SCS. The East Subbasin, the Southwest Subbasin and the continent-ocean transition (COT) zone in the northern margin of the SCS represent different evolution stages of the basin. Due to the differences of the mantle evolution, the mantle potential temperature and the recycled materials in the mantle sources, the MORBs generated at the mid-ocean ridges with different spreading rates show distinct compositions. The large-scale mantle upwelling beneath the SCS during the post-spreading, probably induced by the continuous subduction in the surrounding area, has produced the seamounts at the fossil ridges in the SCS, unlike the volcano chain generated by the mantle plumes. Although the SCS is a small marginal sea, it has recorded incrediblly abundant information and thus provides a rare window for probing the deep earth.

mid-ocean ridge basalts  /  ocean island basalts  /  mantle source  /  South China Sea