The Deformation Characteristic Analysis Of The Baijiling Ductile Shear Zone In South Of Anhui Province

The Jiangnan orogen,located in the joint area between Yangtze block and Cathaysia block,underwent a polyphase deformation during the Caledonian period.Study on the tectonic deformation characteristics of Jiangnan orogen in Caledonian have a great significance to deciphering the early Paleozoic tectonic evolution of the South China continent.The ductile shear zone formed in the early Paleozoic is widely developed in the Jiangnan orogen,as a hotspot,geometry,kinematics,dynamics and chronology of the deformed shear zone draws the attention from geologist.The Baijiling ductile shear zone is located in the southeastern margin of the Yangtze block.Although superficial research have been done in the past and the degree of understood was not enough,which resulted in the deformation characteristics and chronology are still being debated.This paper concentrates on Baijiling ductile shear zone's distribution,shear direction,shear type,deformation temperature and chronology through regional geological surveys,microstructural analysis,quartz crystallography analysis,kinematic vorticity analysis and tectonic chronological analysis.The results shows that the Baijiling ductile shear zone locate in the border region of Anhui province and Zhejiang province,Distributed along the Jiangwan village,Huangjian village,Baiji village,Jiekou village,Sanyang village,about 70km long and strike is 38°,besides,The northeastern of ductile zone is narrow and southeastern is wide.The Baijiling ductile shear zone are demarcated by Changgai village which has distinct foliation,lineation and shear sense.The northern section is characterized by NE-striking sinistral shear zones,wheareas the southern section is characterized by nearly NNE-striking dextral shear zones and thrusting,the kinematic voracity analysis result is greater than 0.9,suggests that the deformation mechanism is manaly of simple shear origin in plan.The microstructural characteristics and quartz c-axis fabric shows that the Baijiling ductile deformation is characterized as a low temperature deformation,but some area is characterized as a high temperature deformation,indicated that ductile shear zone deformed in a low-grade metamorphism condition.The ⁴⁰Ar/³⁹Ar geochronology of sericite of Xiuning formation in Baijiling ductile shear zone is 465Ma,the Changqian formation sericite phyllite ⁴⁰Ar/³⁹Ar age shows that deformation occurs in the Early Paleozoic,these evidence suggest that Baijiling ductile shear zone deformed in the early Paleozoic.Comprehensive analysis of deformation characteristics and chronology of ductile shear zone in the Yangtze and Cathaysia block indicated that sinistral shear commenced at 465Ma,the dextral shear occurred between 449Ma to 429Ma.All evidence suggest that southern of the Nanchang-Jingdezhen-Jiangwan-Sanyangwasgenerallyinvolvedinthe intracontinental orogeny of the South China continent.In addition,the age of Paleozoic ductile deformation of the Jiangnan orogenic belt was earlier than that of the Cathaysia block,the distinct characteristics of the Baijiling ductile zone is likely related to oblique convergence between the Yangtze and Cathaysia domains.