The Ductile Deformation Characteristics of Caledonian Intracontinental Orogeny in the Northeastern Jiangshan-Shaoxing Tectonic Zone:Insights from Magnetic Fabric Study and Its Geodynamic Implication

The Jiangshan-Shaoxing tectonic zone was the northeastern boundary between the Yangtze Block and the Cathaysia Block during the Neoproterozoic and was an intracontinental orogenic belt during late of the early Paleozoic.In this tectonic zone,there develops a lot of mylonite underwent strong ductile deformation and schist,gneiss,and amphibolite with medium and high grade metamorphism which was formed during the late of early Paleozoic.The research of geometry and kinematic of ductile deformation in Jiangshan-Shaoxing tectonic zone is very important to reveal the tectonic process of intracontinental orogeny.This paper uses the anisotropy of magnetic susceptibility(AMS)to determine the ductile deformation geometry and kinematic of Jiangshan-Shaoxing tectonic zone combing with the field survey.In this study,190 specimens of 19 locations and 221 specimens of23 locations from Wangjiazhai section and Lipu-Sizhai section were analyzed.The magnetic foliation over magnetic lineation in both Wangjiazhai and Lipu-Sizhai sections together with the field observations indicated a compressional deformation pattern.3 and 4 strong ductile deformation zones can be established in the Wangjiazhai section and the Lipu-Sizhai section,respectively.According to the magnetic fabric and petro-fabric studies,the Northeastern Jiangshan-Shaoxing tectonic zone suffered two kinds of deformation patterns during the late early Paleozoic,i.e.,the thrusting deformation followed by sinistral shear deformation.