Crustal wide-angle reflection imaging along Lianxian-Gangkou profile in Guangdong province, China

Abstract

A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection (from crystalline basement and Moho) pattern beneath the Yangtze and Cathaysia blocks, and suggests the Wuchuan-Sihui fault is the boundary between them. A cluster of well-developed reflections on Moho and in its underlying topmost mantle probably comes from alternative thin layers, which may be seismic signature of strong interaction between crust and mantle in the tectonic environment of lithosphere extension.

3-D density structure under South China constrained by seismic velocity and gravity data

“…Sichuan basin has a higher density than any other area in South China, especially in the lower crust, which is consistent with that the Yangtze Craton is the oldest basement in South China (Qiu et al, 2000;Zhang et al, 2009b) (Fig. 9e).…”

“…Among all of them, Fig. 6 shows five wide-angle reflection/ refraction profiles: a) Zhubalong-Zizhong (C. ; b) Nanbu-Fushun (Cui et al, 1996); c) Zhuangmu-Anyi (Dong et al, 1998); d) Tunxi-Wenzhou (Zhang et al, , 2008); e) LianxianGangkou Zhang et al, 2009b;Zhao et al, 2013a). The Chinese Academy of Sciences (CAS), the China Earthquake Administration (CEA) and the Ministry of Land and Resources of China (MLR) contributed to perform these seismic profiles during the last 20 years.…”

“…The JiangshanShaoxing fault is generally considered as the north segment of the natural boundary between the Yangtze and Cathaysia blocks (Zhang et al, , 2008Zhao et al, 2013a,b) that are the two major tectonic units of southeastern China (Huang, 1977;Li, 1992). Such a distinction between regional blocks has been proposed on the basis of the age differences of low-grade metamorphic rocks (Wang and Qiao, 1984), occurrence of ophiolite suites (Zhang et al, 1984), stratigraphic records (Ji and Coney, 1985), differences in the lithology of the Precambrian basement (Granitoid Research Group of the Nanling Project, 1989); and more recently according to the observed dissimilarities in composition (Zhang et al, 2008), anisotropy (Zhang et al, 2009a), P-wave velocity (Zhang et al, 2009b) and S-wave velocity (Zhao et al, 2013a). But the standpoints about the boundary in the south part are still quite different.…”