GEOGRAPHY

Researchers have discovered crustal fissures at the northeastern edge of the South China Sea


Recently, Yan Qiong, a researcher at the Key Laboratory of Marginal Sea and Ocean Geology of the Chinese Academy of Sciences, found that there are land crust rifts in the rift basin in the northeast of the South China Sea through multiple seismic profile observations. Related research papers were published in Geochemistry, Geophysics, Earth System. Chen Changliang is the first author of the paper, and Yan Qing and Yu Junhui are the corresponding authors.

Multiple seismic profiles across the rupture zone of the southern depression. Photo courtesy of the research team, the same below

The evolution of passive continental margin is the process of plate tension rupture and magma joining, and the formation of crustal structure patterns is diverse due to various factors. Tension alone can lead to different outcomes, such as brittle fractured crust with geomorphological features with graben barriers, while toughly stretched crust with monotonous thinning. In the northern part of the South China Sea, there are large rift basins of different widths such as southwest Taixi, Pearl River estuary and southeast Qiongdong, and the earth’s crust has undergone a strong thinning process. The revelation of the structural characteristics of the crustal in the passive continental margin of the Northeast China Sea has early fractures and the largest width, which will help to improve the understanding of the crustal properties and magma-tectonic effects in the fracture process of the continental margin of the South China Sea.

Using multi-channel seismic imaging techniques, the researchers found that the Super Tensile Rift Valley in the southern depression of the southwestern Taiwan Basin opened in a V-shape to the northeast. On the west side of the rift axis, the thickness of the earth’s crust is 8.1 km, which deepens further towards the eastern basement, while the mantle rises and becomes shallower, showing an extreme thinning trend. In the eastern rift axis zone, a hemispherical anomalous reflective packet was also observed. The internal reflection coherence of the package is good, but it is not coordinated with the upper sedimentation and lower basement reflection characteristics, and may be caused by peeling mantle serpentinite alteration products, tensile fracture volcanic construction, or early sedimentary remnants of the rift valley. Although the cause of this anomalous reflection packet is uncertain, it is certain that the continental crust has not only undergone super-thinning, but also ruptured to form holes.

Schematic diagram of the causes of crust rupture in the southern depression

The results show that continental crust rupture is not only seen in the terrestrial transition zone of the passive continental margin, but also occurs in the intracontinental rift valley, reflecting the migration phenomenon of the rift valley. “This provides a new case for the multi-style elongation and thinning of the continental crust, which is of great significance for understanding the tectonic-magmatic behavior of the lithosphere under tensile stress and the formation mechanism of the South China Sea.” Yan Qiu said.

The above research was supported by the National Natural Science Foundation of China, Guangdong Special Support Program, Guangdong Basic and Applied Basic Research Fund and other projects. (Source: China Science News, Zhu Hanbin, Li Shu)

Related paper information:https://doi.org/10.1029/2023GC010918



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