Rheomorphic folds in the huanglishu area, Anhui, and their structural significance

The Huanglishu area is located on the east side of the Zhangbaling ultrahigh pressure metamorphic zone. The deformation structures may be classified into the basement ductile deformation zone, ductile-brittle structural schist zone and rheomorphic fold zone. The rheomorphic fold structure is developed in the Sinian and Lower Paleozoic cover rock series east of the Huanglishu-Poliangling fault. From northwest to southeast it is manifested successively by facing down folds, recumbent folds and overturned folds. The rheomorphic folds show gradational relationships with basement ductile and ductile-brittle deformation and have the same deformation kinematic and dynamic features as the latter, which reflects the structural deformation features during the collisional orogeny and exhumation of the Yangtze and North China blocks.