Opening and evolution of the South China Sea constrained by studies on volcanic rocks: Preliminary results and a research design

Abstract

The South China Sea (SCS) is characterized by abundant seamounts, which provide important information about the evolution of the SCS and related deep processes. Cenozoic volcanism in the SCS and its surroundings comprises three stages relative to the spreading of the SCS: pre-spreading (>32 Ma), syn-spreading (32-16 Ma), and post-spreading (<16 Ma). The pre-spreading magmatism predominantly occurs on the northern margin of the SCS and in South China coastal areas and shows a bi-modal affinity. The syn-spreading magmatic activity was very limited on the periphery of the SCS, but may be concentrated in the SCS. However, seafloor samples of this stage are not available yet because of overlying thick sedimentary deposits. Post-spreading magmatism is widespread in the central and southwest sub-basins of the SCS, Hainan Island, Leizhou Peninsula, Thailand, and Vietnam. These are mainly alkali basalts with subordinate tholeiites, and display OIB-type geochemical characteristics. The Dupal isotope anomaly and presence of high-magnesian olivine phenocrysts suggests their possible derivation from the Hainan mantle plume. The temporal and spatial distribution of Cenozoic volcanism in the SCS and its surroundings may be accounted for either by plate stress re-organization before and after SCS spreading, or by ridge suction of plume flow during opening of the SCS. If the latter is the case, the volcanic rocks within the SCS basin may not be typical mid-ocean ridge basalts (MORB). It remains puzzling, however, that the transition between the South China continental margin and the SCS basin does not have features typical of a volcanic rifted margin. Clearly, the relationship between mantle plume and SCS opening needs further evaluation. A better understanding of the link between deep processes and opening of the SCS not only requires enhanced studies on igneous petrogenesis, but also is heavily dependent on systematic sampling of seafloor rocks.

Initiation and evolution of the South China Sea: an overview

“…A mantle plume has also been proposed as the driving force for the formation of the SCS (Flower et al 1998;Xu et al 2012). This model is seemingly supported by seismic tomography, which shows high temperature anomalies beneath the SCS (Huang and Zhao 2006;Zhao 2007).…”

“…The South China Sea (SCS) is the largest marginal sea in the world, with an area of about 3.5 million km 2 , and has been a hot topic among geologists in China and western countries Zhou et al 2011;Xu et al 2012;Huang et al 2013;Li et al 2014a;Liu et al 2014;Tang et al 2014;Clift et al 2015;Lei et al 2015). Tectonically, the SCS is located at the junction of the Eurasian, Indian, Australian, and Pacific Plates and its formation is commonly attributed to interactions among these plates (Sun et al 2006;Xia et al 2006).…”

Tracing the life history of a marginal sea—On “The South China Sea Deep” Research Program

“…However, the "Hainan Plume" has been active mainly since the middle Miocene, and the rifting processes in the SCS appear to have not been accompanied by active volcanic activities. The mismatch in timing and the non-volcanic rifting type, therefore, do not support the connection between mantle plume and the rifting and spreading processes in the SCS [33]. However, there is no doubt on the critical role of mantle plume and volcanism in tectonic evolution and hydrocarbon reservoir formation in the SCS [34], which requires Recently, new data are emerging from the western part of the SCS off the Vietnam coast.…”

South China Sea Tectonics

“…Slab pull and subduction of the proto-SCS under Sabah/Borneo ( Figure F3B) Hayes, 1980, 1983;Holloway, 1982;Hall, 2002), 3. Extension related to an upwelling mantle plume ( Figure F3C) (e.g., Fan and Menzies, 1992;Xu et al, 2012), and 4. Regional extension related to subduction and retreat of the Pacific plate along the western Pacific margin ( Figure F3D) Hayes, 1980, 1983;Shi and Li, 2012).…”