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Deep seismic structure of the northeastern South China Sea: Origin of a high-velocity layer in the lower crust
Wan, KY; Xia, SH; Cao, JH; Sun, JL; Xu, HL; sunjl@scsio.ac.cn
2017
发表期刊JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
卷号122期号:4页码:2831-2858
摘要We present a 2-D seismic tomographic image of the crustal structure along the OBS2012 profile, which delineates the Moho morphology and magmatic features of the northeastern South China Sea margin. The image was created by forward modeling (RayInvr) and traveltime tomographic inversion (Tomo2D). Overall, the continental crust thins seaward from similar to 27 km to similar to 21 km within the continental shelf across the Zhu I Depression and Dongsha Rise, with slight local thickening beneath the Dongsha Rise accompanying the increase in the Moho depth. The Dongsha Rise is also characterized by similar to 4-7 km thick high-velocity layer (HVL) (similar to 7.0-7.6 km/s) in the lower crust and exhibits a relatively high velocity (similar to 5.5-6.4 km/s) in the upper crust with a velocity gradient lower than those of the Zhu I Depression and Tainan Basin. Across the continental slope and continent-ocean transition (COT), which contain the Tainan Basin, the crust sharply thins from 20km to 10km seaward and a similar to 2-3 km thick HVL is imaged in the lower crust. We observed that volcanoes are located only within the COT, but none exist in the continental shelf; the Dongsha Rise exhibits a high magnetic anomaly zone and different geochemical characteristics from the COT. Based on those observations, we conclude that the HVL underlying the COT is probably extension related resulting from the decompression melting in the Cenozoic, whereas the HVL beneath the Dongsha Rise is probably arc related and associated with the subduction of the paleo-Pacific plate. These findings are inconsistent with those of some previous studies. Plain Language Summary We show a seaward thinning trending of the crustal structure across the continental shelf and continent-ocean transition (COT), whereas the crust was slightly and unconventionally thickened beneath the Dongsha Rise accompanying the increase in the Moho depth. The Dongsha Rise is also characterized by similar to 4-7 km thick high-velocity layer (HVL) in the lower crust underlying the thick crust. In the COT, the crust sharply thinned seaward and a similar to 2-3 km thick HVL was imaged underlying the hype-extended crust. We discuss the nature of the HVL in the northeastern South China Sea (SCS) by integrating the volcanic activity, magnetic anomaly, Moho morphology, and geochemistry of the region. We observed that the HVL underlying the COT is probably extension related resulting from the decompression melting in the Cenozoic, whereas that beneath the Dongsha Rise is probably arc related and associated with the subduction of the paleo-Pacific plate. These findings are inconsistent with those of some previous studies. We believe that our viewpoint is first put forward through the detailed demonstration and provides new insights into the rifting processes of the northeastern SCS margin. It will be of great interest to the broad marine geosciences community, particularly those interested in the formation and evolution of the marginal seas.
部门归属[Wan, Kuiyuan; Xia, Shaohong; Cao, Jinghe; Sun, Jinlong; Xu, Huilong] Chinese Acad Sci, South China Sea Inst Oceanol, Key Lab Marginal Sea Geol, Guangzhou, Guangdong, Peoples R China; [Wan, Kuiyuan] Univ Chinese Acad Sci, Coll Earth Sci, Beijing, Peoples R China
资助项目MSG
文献类型期刊论文
条目标识符http://ir.scsio.ac.cn/handle/344004/16485
专题中科院边缘海地质重点实验室
通讯作者sunjl@scsio.ac.cn
推荐引用方式
GB/T 7714
Wan, KY,Xia, SH,Cao, JH,et al. Deep seismic structure of the northeastern South China Sea: Origin of a high-velocity layer in the lower crust[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2017,122(4):2831-2858.
APA Wan, KY,Xia, SH,Cao, JH,Sun, JL,Xu, HL,&sunjl@scsio.ac.cn.(2017).Deep seismic structure of the northeastern South China Sea: Origin of a high-velocity layer in the lower crust.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,122(4),2831-2858.
MLA Wan, KY,et al."Deep seismic structure of the northeastern South China Sea: Origin of a high-velocity layer in the lower crust".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 122.4(2017):2831-2858.
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