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学科主题: Geochemistry & Geophysics
题名: Crustal structure across the xisha trough, northwestern South China Sea
作者: Qiu, XL ; Ye, SY ; Wu, SM ; Shi, XB ; Zhou, D ; Xia, KY ; Flueh, ER
通讯作者: Qiu, XL, Chinese Acad Sci, S China Sea Inst Oceanol, 164 W Xingang Rd, Guangzhou 510301, Peoples R China
关键词: Xisha Trough ; rifting ; crustal structure ; Moho interface ; ocean bottom hydrophone (OBH)
刊名: TECTONOPHYSICS
发表日期: 2001
卷: 341, 期:40547, 页:179-193
收录类别: sci
部门归属: Chinese Acad Sci, S China Sea Inst Oceanol, Guangzhou 510301, Peoples R China; Res Ctr Marine Geosci, GEOMAR, D-24148 Kiel, Germany
项目归属: 海洋地质
摘要: Located at the northwestern part of the South China Sea (SCS) between the Hainan and Xisha (Paracel) Islands, the Xisha Trough represents a failed rift in conjunction with the opening of the SCS between 32 and 17 Ma. From west towards east within a scale of several hundred kilometers, it presents all major stages of the rifting process, and thus, provides an ideal place to study the rifting process in great details. In the autumn of 1996, a joint team of Sino-German scientists carried out a wide-angle seismic experiment across the Xisha Trough with 10 ocean bottom hydrophones (OBH) along a 237-km NNW-SSE-oriented profile, which was surveyed in 1987 with multi-channel seismic (MCS) method by BGR of Germany and SOA of China. Favorable weather conditions and the powerful 4 x 12-1 air gun array rendered very good quality data with seismic signals observed at the offset of up to 110 km, A detailed velocity-depth model was obtained by using an interactive trial-and-error 2D ray-tracing method. Interpretation of the NICS data published by BGR provides very good geometrical constraints of the complex upper crustal structure, which is characterized by fault blocks, half-horsts and half-grabens filled with syn- and post-rift Cenozoic sediments. The velocity model in turn confirms the major structure outlined by the interpretation of the MCS data, showing a varying sedimentary layer between I and 4 km of thickness and velocities between 1.7 and 4.5 km/s. The P-wave velocity of 5.5 km/s on the top of the crystalline basement is relatively low, suggesting strong weathering. Within the crystalline crust, the velocity increases downward continuously to 6.8 km/s at the bottom of the crust without a clear differentiation in the middle crust, showing clearly its continental nature even beneath the Xisha Trough. The Moho is marked by a sharp first-order interface with a velocity of 8.0-8.1 km/s at the uppermost mantle. The Moho depth is 15 km beneath the center of the trough and increases gradually to more than 25 kin towards north and south, corresponding to an extreme thinning of the pre-rift continental crust from more than 25 kin under the coast line to only 8 kin beneath the Xisha Trough. The similar velocity structure of the continental nature on both sides of the Xisha Trough suggests a homogeneous pre-rift continental setting. The sharp Moho and the lack of high velocity body (HVB) in the lower crust imply no magmatic underplating, which is very different to interpretations across the eastern part of the continental margin in northern South China Sea. The intense faulting in the upper crust, the strong but rather symmetrical crustal thinning centered at the Xisha Trough and the close neighborhood to the open SCS NW subbasin suggest a pure shear rifting, which failed most likely at the phase shortly before the continental breakup. (C) 2001 Elsevier Science B.V. All rights reserved.
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WOS记录号: WOS:000172613000010
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内容类型: 期刊论文
URI标识: http://ir.scsio.ac.cn/handle/344004/4688
Appears in Collections:中科院边缘海地质重点实验室_期刊论文

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Qiu, XL; Ye, SY; Wu, SM; Shi, XB; Zhou, D; Xia, KY; Flueh, ER.Crustal structure across the xisha trough, northwestern South China Sea,TECTONOPHYSICS,2001,341(40547):179-193
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