Imaging the Western Boundary of the Sichuan Craton from Multiple Geophysical Observations  

作　　者：Qihang Yin Xi Xu Xiaodong Yang Xuhua Shi Lei Wu Andrew V.Zuza Liu Yang Hefeng Tian Yuanhai Shu Shufeng Yang 

机构地区：[1]School of Earth Sciences,Zhejiang University,Hangzhou,310058,China [2]China Aero Geophysical Survey and Remote Sensing Center for Natural Resources,China Geological Survey,Beijing,100083,China [3]SINOPEC Key Laboratory of Geophysics,Nanjing,211103,China [4]Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou,511458,China [5]Nevada Bureau of Mines and Geology,University of Nevada,Reno,Nevada,89557,USA [6]School of Mechanical and Electrical Engineering,Hubei Open University,Wuhan,430074,China

出　　处：《Journal of Earth Science》2024年第6期1860-1877,共18页地球科学学刊（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.U22B6002,42422402,41902202 and 42276222);the SINOPEC Key Laboratory of Geophysics(No.FW0399-0029);the Second Tibetan Plateau Scientific Expedition and Research(No.2019QZKK00708);the Development Fund of South China Sea Institute of Oceanology of the Chinese Academy of Sciences(No.SCSIO202207);the Special Fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB22B23)。

摘　　要：The boundary between cratonic and orogenic lithospheres is a significant seismogenic zones marked by intense lithospheric deformation.The Sichuan Craton(SCC),as a key tectonic block bordering eastern Tibetan Plateau,resists the eastward escape of plateau's crustal materials,resulting in the uplift of the Songpan-Ganzi Block(SGB)and crustal deformation of the Longmenshan tectonic belt(LMTB).To elucidate the compressional structures and deformational modes of the LMTB and SCC,it is essential to accurately determine the location and geometry of the SCC'western boundary.To investigate this issue,the lithospheric properties of the obducted SGB,underthrusting SCC,and LMTB were analyzed using various geophysical data,including seismic reflection profiles,magnetotellurics,aeromagnetics,gravity,and seismic tomography.The SGB crust is characterized by low magnetism,seismic velocity,resistivity and Bouguer gravity,whereas the SCC crust exhibits non-uniform high magnetism,seismic velocity,resistivity and Bouguer gravity.The LMTB,as the boundary between the SGB and SCC,exhibits geophysical characteristics similar to those of the SCC in the southern and central segments.The integration of these geophysical observations indicate that the SCC's western boundary is situated west of the Wenchuan-Maoxian fault zone in the southern and central segments,exhibiting distinct westward wedging and underthrusting.However,this boundary aligns with the Yingxiu-Beichuan fault in the northern segment,without significant underthrusting.The irregular geometry of the SCC's western boundary further elucidates the variation in structural deformation along the LMTB.By comparing crustal thickness and lithospheric strength between the SGB and SCC,this study posits that the differing crustal strength between tectonic blocks may control the irregular geometry of the SCC's western boundary.

关 键 词：Sichuan Craton Longmenshan tectonic belt geophysical imaging lithospheric structure tectonic wedging GEOPHYSICS structural geology 

分 类 号：P548[天文地球—构造地质学]