摘要
深部地震和重力资料反演揭示了南海北部陆缘地壳结构在总体上由北部的华南沿海（厚约30km）向南部的洋盆（5──8km）逐渐减薄。南海的近SN向拉张不仅造成南北方向地壳结构的巨大变化，也造成东西向的明显变化。在南海北部陆缘的西部，局部拉张产生了一系列裂谷构造。西沙海槽作为一条狭窄的陆内裂谷向西延伸，海槽南北两侧地壳厚度超过25km，海槽中部地壳减薄至不足10km。西端的莺歌海盆地地壳厚仅5km，缺少明显的壳内反射－折射。在珠江口盆地中部，地壳厚度在下陆坡明显减薄，地壳下部存在较薄的（3──4km）高速层（地震波速7．2──7．5km·s－1）；在珠江口盆地东部，地壳底部存在约 10km厚、300km宽的高速层。在台湾地区，由于弧陆碰撞，曾经减薄的陆壳在碰撞带增厚，莫霍面深度超过30km。南海北部陆缘在裂谷拉张和海底扩张期间岩浆活动平静，表明南海北部陆缘为非火山型陆缘。
The crustal structure of northern margin of the South China Sea and SouthChina is revealed by inversion of deep seismic data and gravity data. The crust thicknessgenerally decreases southward, from about 30 km in offshore South China to 7--8 km inthe central basin. The roughly SN extens1on in the South China Sea resulted in greatvariation of crustal structure not only cross the margin but also along the margin. In thewest of the margin, Xisha Trough extends westward as a narrow intra--continental riftfrom the central basin. In Xisha Trough the crust thickness varies from 25 km plus overthe two sides to 10 km minus over the center. The crust thins even to 5 km over theYinggehai Basin in the westernmost. In the central Zhujiang River mouth basin, thecrust thins rernarkably over the lower slope. A high P wave velocity (7. 2--7. 5 km·s -l )layer with a thickness of 3--4 km exists under the slope. In the eastern ZhujiangRiver mouth basin, the crust thickens locally over the continental shelf; in the base ofcrust, a high P wave ve1ocity layer is more than 10 km thick and 300 km wide. OverTaiwan Region, the once thinned continental crust becomes thick because of the arc--conti-nent collision since middle Miocene. The Moho discontinuity there becomes deeper than30 km. The quiescence of magmatism during rifting and seafloor spreading implies thatthis margin belongs to the non--volcanic type.
出处
《热带海洋学报》
CAS
CSCD
北大核心
2002年第2期1-12,共12页
Journal of Tropical Oceanography
基金
国家重点基础研究发展规划项目(G2000046702-04)
中国科学院知识创新工程重要方向项目(KZCX2-117-01)
国家高技术研究发展计划课题(2001AA610101)
中国科学院南海海洋研究所边缘海地质与古环境开放实验室基金资助项目(BYH01A06)
