科研之友
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摘要
The large-scale strike-slip Tan-Lu Fault Zone (TLFZ) and Xiangfan-Guangji Fault Zone (XGFZ) both terminate in the southeastern corner of the Dabie Orogen at an angle of almost 90 degrees, and this corner therefore provides a very good natural laboratory for understanding the mechanism by which large-scale strike-slip faults terminate. We present new geochronological and structural data for the southeastern tip of the XGFZ and the southwestern tip of the TLFZ. The NW-SE-striking XGFZ records ductile shearing in its northwestern segment, characterized by discrete dextral shear zones that formed at temperatures of 350-400 degrees C, as indicated by quartz c-axes fabrics and microstructures. In the southeastern segment of the XGFZ, WNW-ESE-trending thrusts are displayed. The NE-SW-striking TLFZ is characterized by discrete NE-SW-trending sinistral ductile shear zones in the Qianshan-Tongcheng segment, brittle left-lateral strike-slip faults in the Taihu-Qianshan segment, and thrusts to the south of Taihu. The trends of these thrusts change progressively southward from NE-SW to ENE-WSW and E-W. New zircon U-Pb dating results and previous cooling biotite 40Ar/39Ar ages constrain the timing of shearing in the XGFZ to 112-102 Ma (late Early Cretaceous), which is the same as the age of faulting in the TLFZ (110-102 Ma). The large-scale strike-slip TLFZ and XGFZ both terminate at their tips as thrusts. We suggest that interactions between the two faults led to the kinematic changing from strike-slip to thrusting, with this playing an important role in controlling the termination of these two large-scale intersecting strike-slip faults. The dextral shearing of the NW-SE-trending XGFZ, the sinistral shearing of the NE-SW-trending TLFZ, and the nearly E-W-trending thrust faults all indicate continental-scale N-S compression in eastern China during the late Early Cretaceous. This compression resulted from rapid NNW-ward oblique subduction of the Paleo-Pacific Plate.
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单位河海大学
