Evolution of Yiwulüshan metamorphic core complex in western Liaoning constrained by ~(40)Ar/~(39)Ar thermochronology

The Yiwulushan metamorphic core complex(MCC) in western Liaoning experienced two stages of extensional activities. In the early stage, a loop-shaped ductile shear zone, called the Yiwulushan shear zone,developed around the central Yiwulushan pluton. And then its southwestern part was truncated by the Waziyu extensional shear zone. The40Ar/39Ar thermochronology results obtained from mylonites, schists and gneisses in different parts of the core complex show large age span, ranging from 159 to 116 Ma, such as hornblende ages of159–129 Ma, muscovite ages of 139–124 Ma, biotite ages of 139–116 Ma. The ages in the east are between159–150 Ma, and that in the west are largely 129–116 Ma. They represent times of two extension activities,respectively.