2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 146-2
Presentation Time: 1:45 PM


DONG, Shu-Wen1, LI, Ting-Dong1, GAO, Rui2, LV, Qing-Tian1, CHEN, Xuan-Hua1 and SINOPROBE, Team1, (1)SinoProbe Center, Chinese Academy of Geological Sciences, Beijing, 100037, China, (2)State Key Laboratory of Continental Tectonics and Dynamics, Key Laboratory of Earthprobe and Geodynamics, MLR, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China, swdong@cags.ac.cn

The tremendous structural changes of the continental lithosphere in China has been constrained by major tectonic events in East Asia since Triassic. Deep seismic reflection profiling is the most effective method to discover the related tectonic evolution. The SinoProbe, a deep seismic exploration in China, has successfully collected ca.6000km length deep seismic reflection profiling data during the last six years. Results of the deep seismic profiling proves the SinoProbe team made remarkable achievements. For the first time, the SinoProbe has obtained deep seismic reflection evidence for the Moho surface below the thick crust of central Tibet for the first time, and revealed dipping fabrics in the lithospheric mantle beneath northeastern China, in which, bidirectional facing subduction beneath the Songliao Basin is seen. The North China profile provides large evidence for understanding the plate convergence, continental crustal growth during the Central Asia Orogeny. In addition, the Lower Yangtze profile links the North China and the South China Blocks in a view of deep crust and lithospheric structures, revealing formation of the metallogenic belt in the Middle and Lower Reaches of the Yangtze River. The South China profile gives an opportunity for the perspective view of the complex structure of the South China Block, helping understand the deep processes of a formation of a cratonic South China. In South Tibet, profiles revealed deep crust and Moho structure, including north dipping strong reflectors in the lower crust, strong reflectors beneath the Gangdese Magmatic Belt, and flower structure of the Kalakunlun fault in the upper crust. The deep seismic reflection profile in Central Tibet reveals the Moho has been cut off ~6.2km by the Bangong Co-Nujiang suture. The profile in northeastern Tibet revealed duplex structure of the upper crust, nearly horizontal detachment in the lower crust, and mantle involved offset of Moho. The Eastern Tibet profile shows that the crust of the Yangtze Block extends far from the Longmenshan fault zone into the Longriba fault zone in eastern Tibet. The results of deep seismic profiling, integrated with magnetotelluric sounding, suggest that the lower curst channel flow may have been blocked in the eastern part of the Tibet.