The Structure Of The Crust And Upper Mantle In Eastern South China From Teleseismic Receiver Function

Located in the intersection area of Eurasian Plate, Pacific Plate and Philippine sea plate, the eastern of South China Block(SCB), one important part of tectonic framework of eastern Eurasia edge, is one ideal and natural laboratory for studying plate interaction. In the thesis, the receiver function method is adopted to explore the crust structure of eastern SCB.Firstly, the study progress of geology and crustal and upper mantle structure of eastern SCB is briefly reviewed. Then, we collected tele-seismic records from 35 temporary and 58 permanent stations setting in the study area from June 2012 to June 2014, and calculated 6784 P wave receiver functions. H-kappa stacking method was used to get the crustal thickness and Vp/Vs ratio, and the CCP stacking method to get the Moho shape from inland to coastal areas in the eastern of South China, and the 410 km and 660 km discontinuity surface was also get. Combination with the results of other geophysics method, we give the preliminary discussion on continental dynamics of eastern SBC.The main results of the thesis are summarized as follows:(1) The crustal thickness of the eastern SBC ranges from 28 km to 34 km, it is gradually thinning up and down from the inland to the coast. The crust is relatively thin in coastal areas and northwestern Jiangxi region, and relative thick in the northwest of Jiangxi and the southeast of Fujian. The Vp/Vs ratio is between 1.61 and 1.83, the corresponding poisson’s ratio is between 0.21 and 0.28, the wave velocity ratio (poisson’s ratio) increases from the inland to the coast. Fuzhou and Zhangzhou have higher poisson’s ratios, which may be caused by partial melting in the deep. The crust in the study area are mainly composed of medium and acid rock, partly affected by strong upwelling mantle material, magnesium iron with a significant increase in crustal rocks, which results in poisson’s ratio increases.(2) Along the Jiujiang, Jiangxi Province to Ninghua, Fujian Province section, the average Vp/Vs ratio is between 1.65 and 1.75, its corresponding poisson’s ratio is between 0.21 and 0.26, they may represent the poisson’s ratio of inland. Poisson’s ratio shows that crustal rocks in the study area are felsic, and the crustal structure in the study area is relatively stable, crust-mantle material exchange vertical activity is weak. Along The Vp/Vs ratio in Pingxiang-Guangfeng fault is significantly higher, may be caused by remnants of neoproterozoic ophiolitic melange belt in the deep, meanwhile, Pingxiang-Guangfeng fault can be considered as the extension of Jiangshao coherence belt, it is the convergent boundary of Yangtze block and Cathaysia block in the north of Jiangxi Province.(3) The main velocity discontinuity of the upper mantle in the eastern of South China 410 km and 660 km discontinuities are found no obvious mutation or ups and downs, the upper mantle transition zone thickness is consistent with the global average, it suggests that the eastern of South China continent, mantle transition zone are keeping normal temperature, it also shows that the eastern region of South China continent, the mantle transition zone are not subjected to Eurasia plate and the Philippine plate collision.