Midcrust kinematics in intracontinental oblique convergence

The Zhangbaling belt, a greenschist-blueschist-facies metamorphic belt, is the largest metamorphic terrane exposed ∼20 km east of the Tan-Lu fault between the Dabie and Sulu belts in SE China and is characterized by a subhorizontal foliation, a belt parallel lineation, and top-to-south sense of shear, determined from quartz c-axis fabrics. The Zhangbaling schist is conformably overlain by metatillite/phyllite and a sedimentary cover without major unconformities from Paleozoic to early Mesozoic time. The structural style of the brittle cover is characterized by a SE-verging foreland thrust belt.; The Fucha Shan metamorphic zone is composed of lower-amphibolite facies gneiss exposed east of the Tan-Lu fault, ∼30 km south of the Zhangbaling belt and is characterized by subvertical foliation, subhorizontal lineation, and isoclinal folds. Shear-sense of the zone, determined from quartz c-axis fabrics, is consistently sinistral with a component of zone-perpendicular contraction.; Finite strain analysis of the metatillite/phyllite in the Zhangbaling belt shows that the deformation of the metatillite/phyllite zone is plane strain. Kinematic vorticity analysis (Wk) demonstrates that the Zhangbaling schist were produced in a two dimensional general shear with a larger vertical coaxial component in the south (Wk = ∼0.75) and small coaxial flow in the north (Wk = 0.80). Integrated results of finite strain modeling of the schist and finite strain analysis of the metatillite/phyllite suggest that this mid-upper crustal section experienced at least ∼300% lineation-parallel stretching and the thickness of this crustal section was reduced from ∼15 km to ∼5 km in a plane-strain dominated general shear.; 40Ar/39Ar white mica ages date the deformation of the Zhangbaling schist at ∼235-240 Ma, coeval with peak metamorphic ages of ultra-high-pressure metamorphism in Dabie Shan. Fabric-forming biotite and hornblende from the Fucha Shan gneiss yield cooling ages of ∼120 Ma to ∼135 Ma with pre-Cretaceous cooling.; The Zhangbaling belt formed along the Proto-Tan-Lu fault, during oblique convergence between north and south China in early Triassic time. Fucha Shan zone may represent the first activation the Tan-Lu fault in Cretaceous, or developed as the crustal root coupled by an attachment zone represented by the Zhangbaling schist in this Triassic intra-continental oblique convergence.