Opening of the South China Sea by Dextral Splitting of the East Asian Continental Margin
Opening of the South China Sea by Dextral Splitting of the East Asian Continental Margin
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发表时间：
2002
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通讯作者：
Wu Shi-min
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作者：
Wu Shi-min
南海的成因一直是研究的热点，因为它与特提斯和环太平洋两大汇聚带的相互作用以及西太平洋边缘海的地球动力学有关。日本海和南海作为西太平洋边缘海内带的一部分，在海盆形成的时代、形态和地形、多轴多阶段的海底扩张、向西伸展的地壳拉张作用以及地幔地球化学等方面具有许多共同特征。这可能意味着它们的共同起源。南海海盆呈楔形。南海海底扩张和大陆架裂陷具有向南跳跃、向西传播发展的特征。地壳向西伸展减小。这是一个向西倾斜的剪刀差，其张开是由于东亚大陆边缘在近南北向的右旋剪切作用下发生分裂所致。中南半岛半岛及南海海盆开启时发育大量南北走向的右旋断裂，表明当时存在右旋应力。现今的南海东部边界被一条南北走向的俯冲带所占据，而不是一条大的右旋断层;这可能归因于菲律宾群岛沿着现今的马尼拉海沟的对接和仰冲破坏了先前的构造。晚中生代以来，西太平洋板块、特提斯板块印度段和特提斯板块澳大利亚段均发生了不同方向和速度的向欧亚大陆的汇聚。这些汇聚力量相互竞争、相互复合，构成了东亚边缘“大剪切”发展的地球动力学背景。这种剪切作用的特征是左旋压扭和右旋张扭交替进行，可能是由会聚引起的地幔流驱动的。在印藏辐合影响占优势的时期，东亚边缘在右旋扭张应力场作用下发生了分裂，进而打开了西太平洋边缘内带的南海等海域
The origin of the South China Sea has long been a hot subject of research, as it is related to the interaction of two large convergent zones, the Tethys and the Circum-Pacific, as well as to the geodynamics of the marginal seas of the West Pacific. The Sea of Japan and the South China Sea, as part of the inner zone of the West Pacific marginal seas, have many common features such as the age, shape and topography of the sea bas-in , the multi-axial and multi-stage seafloor spreading, westward propagating crustal extension, and the mantle geochemistry. These may imply their common origin. The South China Sea basin has a cuneiform shape. The seafloor spreading in the South China Sea and the rifting of its continental shelf were characterized by south-ward jumping and westward propagating development. The crustal extension decreased westward. These may be portrayed as a westward tipping scissors, whose opening was caused by the splitting of the East Asia conti-nental margin under approximately N-S oriented dextral shearing. Numerous N-S running dextral faults devel-oped in the Indochina Peninsula and within the South China Sea basin when it was opening, indicative of the existence of dextral stress at the time. The present eastern border of the South China Sea is occupied by a N-S running subduction zone, not a large dextral fault; this may be ascribed to the destruction of previous structure by the docking and obduction of the Philippine Archipelago along the present Manila trench. Since the Late Mesozoic, convergence toward Eurasia with various direction and speed occurred in the West Pacific domain, the Indian segment of the Tethys domain, and the Australian segment of the Tethys domain. These convergent forces competed and compounded each other, forming the geodynamic background for the development of " large shearing" in the margin of East Asia. This shearing was characterized by the alternative sinistral transcompression and dextral transtension, and might be driven by convergence-induced mantle flow. In the period when the influence of the India-Tibet convergence predominant, the East Asian margin was split under the stress field of dextral transtension, and then opened the South China Sea and other seas of the inner zone of the West Pacific margin