Comprehensive Study Of Receiver Function And Gravity Data For Obtaining Crust-upper Mantle Interface Structures In South China

The South China is located at the convergence of Eurasian,Pacific and IndianAustralian plates,and the geological structure and lithospheric deformation are extremely complex.Crystalline basement interface,Moho interface and the lithosphere bottom interface are important interfaces within the lithosphere,and their depth undulation can provide important evidences for understanding the deformation mechanism of the crust and lithosphere.In the paper,the regional broadband seismic receiver function and gravity data are used to invert the three interface structure of South China,that is,the depth of crystalline basement interface is obtained by using the frequency domain density interface inversion method,and the depth of Moho is obtained by using the receiver function H-? stacking and receiver function NA(neighbourhood algoruthm)inversion method,and the depth of lithospheric bottom interface is obtained by using the joint of gravity,geoid and topography data.The main understanding of this paper are as follows:(1)The undulating depth of the crystalline basement interface in South China is between 3~15km.The crystalline basement interface of Yangtze block undulates largely,ranging 5~15km.The basement depth of Sichuan basin is 5~12km,and the basement depth of Jiangnan basin is 6~10km.The crystalline basement of Cathaysia block is flat and the depth is 3~10km.The complex undulation feature of the crystalline basement interface reflects the control effects of multiple tectonic events on the internal deformation of the continental crust in South China.(2)The undulating depth of Moho in South China is between 25~49km,with the average depth of 37 km,and the overall trend is deep in northwest and shallow in southeast.The Moho of Yangtze block undulates largely,ranging 30~49km,the depth of Moho of Sichuan basin is 40~43km,the depth of Moho in the Jiangnan orogenic belt is 30~35 km.The Moho of Cathaysia block is flat and the depth is 26~30km.Along Jingmen-Changde-Wugang-Hechi-Baise line presented a NNE-trending gradient belt of moho.The depth of Moho rises about 4km from west to east.The undulation feature of Moho in South China reflects the thinning of the eastern crust,which is supposed to be closely related to the subduction of the Western Pacific plate in the Mesozoic.(3)The depth of the lithospheric bottom interface in South China is between 100 ~190km,with a difference of 90 km on both sides of the East and West,and the overall trend is deep in west and shallow in east.The depth of the lithospheric bottom interface under Yangtze block is 140~190km,the interface depth of Sichuan basin and its peripheral lithosphere up to 180 km.and the interface of the Cathaysia block lithosphere is relatively shallow and flat,roughly in 110~120km,the shallowest up to 100 km.Along Wuhan-Pingxiang-Chenzhou-Zhaoqing and Yichang-Jishou-Tongren-Baise line respectively presented two NNE-trending gradient belts of lithospheric bottom interface,lithospheric bottom interface from west to east progressive uplift.The undulation feature of lithospheric bottom interface in South China reflects the thinning of the eastern lithosphere,which is supposed to be closely related to subduction of the Western Pacific plate in the Mesozoic.