Abstract：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.
[1] Koppers A A P. On the 40Ar/39Ar dating of low-Patassium ocean crust basalt from IODP Expedition 349, South China Sea[C]//AGU Fall Meeting Abstract, 2014.
[2] Li C F, Xu X, Lin J, et al. Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349[J]. Geochemistry, Geophysics, Geosystems, 2014, 15(12):4958-4983.
[3] Ding W, Sun Z, Dadd K, et al. Structures within the oceanic crust of the central South China Sea basin and their implications for oceanic accretionary processes[J]. Earth and Planetary Science Letters, 2018, 488:115-125.
[4] Liu H Q, Yumul Jr G P, Dimalanta C B, et al. Western Northern Luzon isotopic evidence of transition from Proto-South China Sea to South China Sea fossil ridge subduction[J]. Tectonics, 2020, 39(2):e2019TC005639.
[5] Wu J, Suppe J, Lu R, et al. Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods[J]. Journal of Geophysical Research:Solid Earth, 2016, 121(6):4670-4741.
[6] Zhang G L, Luo Q, Zhao J, et al. Geochemical nature of sub-ridge mantle and opening dynamics of the South China Sea[J]. Earth and Planetary Science Letters, 2018, 489:145-155.
[7] Wang X C, Li Z X, Li X H, et al. Coexistence of an ancient mantle reservoir and young recycled materials in the source region of a young mantle plume:Implications for potential linkage between plume and plate tectonics[J]. Earth and Planetary Science Letters, 2013, 377-378:248-259.
[8] Yang F, Huang X L, Xu Y G, et al. Plume-ridge interaction in the South China Sea:Thermometric evidence from Hole U1431E of IODP Expedition 349[J]. Lithos, 2019, 324-325:466-478.
[9] Yang F, Huang X L, Xu Y G, et al. Magmatic processes associated with oceanic crustal accretion at slow-spreading ridges:Evidence from plagioclases in mid-ocean ridge basalts at the South China Sea[J]. Journal of Petrology, 2019, 60:1135-1162.
[10] Yan Q, Shi X, Metcalfe I, et al. Hainan mantle plume produced late Cenozoic basaltic rocks in Thailand, Southeast Asia[J]. Scientific Reports, 2018, 8(1):2640.
[11] Fan C, Xia S, Zhao F, et al. New insights into the magmatism in the northern margin of the South China Sea:Spatial features and volume of intraplate seamounts[J]. Geochemistry, Geophysics, Geosystems, 2017, 18(6):2216-2239.
[12] Sun Z, Lin J, Qiu N, et al. The role of magmatism in thinning and breakup of the South China Sea continental margin[J]. National Science Review, 2019, 6(5):871-876.
[13] Wang X C, Li Z X, Li X H, et al. Temperature, pressure, and composition of the mantle source region of Late Cenozoic basalts in Hainan Island, SE Asia:A consequence of a young thermal mantle plume close to subduction zones?[J] Journal of Petrology, 2012, 53:177-233.
[14] Xu YG, Wei J X, Qiu H N, et al. Opening and evolution of the South China Sea constrained by studies on volcanic rocks:Preliminary results and a research design[J]. Chinese Science Bulletin, 2012, 57:3150-3164.
[15] Lin J, Xu Y, Sun Z, et al. Mantle upwelling beneath the South China Sea and links to surrounding subduction systems[J]. National Science Review, 2019, 6(5):877-881.
2020, Vol. 38 
