Temporal variations in the dynamic evolution of an overriding plate: Evidence from the Wulong area in the eastern North China Craton, China

Abstract

Abstract The evolution of overriding-plate deformation, and the mechanisms responsible for this deformation, are debated. One area where these processes can be investigated is the eastern North China Craton (NCC) in China, which was situated in an overriding-plate position relative to the subducting Paleo-Pacific Plate during the Jurassic and Cretaceous. Here we constrain the structural evolution of the Jurassic and Cretaceous using new structural, stress field, and geochronological data from the Wulong area. The results show that the first phase of deformation (D1) produced a series of SE-dipping reverse shear zones and parallel folds in response to NW-SE shortening at 157–146 Ma (Late Jurassic). Based on microscopic observations and quartz c-axis analysis, it is suggested that the temperature during D1 deformation was 500 ± 50 °C. A second phase of contractional deformation (D2) at 146–132 Ma (earliest Early Cretaceous) gave rise to numerous NE-SW–striking sinistral faults and shear zones. The majority of D2 structures display ductile fabrics in the southwest of the Wulong area and brittle deformational features in the northeast, thus indicating enhanced exhumation in the former area. Microstructures of D2 sinistral shear zones indicate deformation temperatures of 300–400 °C. Inversion of fault slip data from the sinistral faults demonstrate that N-S compression was responsible for the D2 structures. The third phase of deformation (D3) was related to WNW-ESE extension during the middle to late Early Cretaceous (132–100 Ma). This extensional phase produced a series of NE-SW–striking normal faults and reactivated pre-existing structures. Dikes and plutons were emplaced during the D3 deformation, synchronous with the peak destruction of the NCC. Our results indicate that the eastern NCC showed temporal variations in stress and strain during the Jurassic and Cretaceous. Consistent with the slab-driven model, we suggest that this behavior represents the response of the overriding-plate to changes in subduction kinematics.