Characteristics of the Huayangchuan ductile shear zones in the Xiaoqinling Mountains, Shaanxi, China, and its regional tectonic significance

The Huayangchuan ductile shear zone in the Xiaoqinling Mountains, Shaanxi, formed in the Neoarchean Taihua Group complex. Field survey and microscopic observation have revealed this ductile shear zone is a deep-level zone, consisting of tectonic schist and augen gneiss, which have features of thrust and sinistral strike-slip oblique subduction. 40Ar/39Ar dating of biotite from tectonic schist in the ductile shear zone yielded a plateau age of 419±0.6 Ma and an inverse isochron age of 417±0.8 Ma. Therefore the authors think that the Huayangchuan ductile shear zone and its related regional principal tectonic deformation of the Xiaoqinling Mountains formed in the Caledonian event at 419± Ma.