Structural and rheological features of the western Liaoning metamorphic core complex corridor: Indications for Late Mesozoic extension of the eastern North China Craton

Abstract

The Xingcheng-Taili ductile shear zone and Yiwulüshan metamorphic core complex formed during crustal extension of the eastern North China Craton. The ENE-trending Xingchegn-Taili sinistral ductile shear zone developed along the margins of the western Liaoning metamorphic core complex corridor within upper greenschist to lower amphibolite facies-grade metamorphic conditions. Shearing was associated with two different ductile deformation events in the Yiwulüshan metamorphic core complex, i.e. (1) an earlier dextral shearing and (2) later sinistral shearing. The earlier dextral ductile shear zone is mainly characterized by simple-shear dominated general shear with L=S and LS tectonites under upper greenschist to lower amphibolite facies conditions. The orientation and fabrics of L=S tectonites indicate that the later ductile deformation consists of almost equally simple and pure shear and constrains a low-middle-temperature sinistral shear within upper greenschist facies-grade conditions. The estimation of rock rheological parameters from dynamically recrystallized grain sizes of quartz indicates that the high-temperature shear zone has formed under lower stress conditions and higher strain rates, while opposite features exist in the lower temperature shear zone. The initiation of deformation of the western Liaoning metamorphic core complex corridor might have started between 136Ma and 120Ma and its termination time was at ca. 100Ma. The NE-ENE strike-slip ductile deformation in the western Liaoning metamorphic core complex corridor, within the Eastern Block of the North China Craton, was resulted from roll-back of the subducting Pacific plate beneath the North China Craton along the eastern Asian margin during Early Cretaceous times.