Structural,^(40)Ar/^(39)Ar Geochronological and Rheological Feature Analysis of the Guoxuepu Shear Zone:Indications for the Jitang Metamorphic Complex in the Northern Lancangjiang Zone  

作　　者：FENG Yipeng WANG Genhou WANG Shulai LI Dian WANG Huan LU Yang LIU Han ZHANG Peilie 

机构地区：[1]Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012,China [2]School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China [3]College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China [4]Rock Analysis Laboratory,Regional Geology Survey Institute of Hebei Province,Langfang,Hebei 065099,China [5]Chengdu Center,China Geology Survey,Chengdu 610081,China

出　　处：《Acta Geologica Sinica(English Edition)》2024年第1期32-49,共18页地质学报（英文版）

基　　金：financially supported by the China Geological Survey Scientific Research Project(Grant Nos.DD20190167 and DD20190053);the National Natural Science Foundation of China(Grant No.42172259).

摘　　要：The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jitang metamorphic complex was determined.The macro-and microstructural analyses of the ductile detachment shear zone(Guoxuepu ductile shear zone,2–4 km wide)between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast.The presence of various deformation features and quartz C-axis electron backscatter diffraction(EBSD)fabric analysis suggests multiple deformation events occurring at different temperatures.The average stress is 25.68 MPa,with the strain rates(έ)ranging from 9.77×10^(−14)s^(−1)to 6.52×10^(−16)s^(−1).The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern.The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88,implying that the shear zone is dominated by simple shear.The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09±0.38 Ma.It is suggested that,coeval with the initial Indo–Eurasian collision,the development of strike-slip faults led to a weak and unstable crust,upwelling of lower crust magma,then induced the detachment of the Jitang metamorphic complex in the Eocene.

关 键 词：^(40)Ar/^(39)Ar dating strain pattern VORTICITY EBSD Guoxuepu shear zone Jitang metamorphic complex 

分 类 号：P588.3[天文地球—岩石学] P597.3[天文地球—地质学]