The Tectono-magmatic Interactions Of Liaonan Metamorphic Core Complex

Based on the pre-existing geological study, this research measured the attitudes of lineation and foliation, took a lot of samples during the fieldwork, then analysed the data and did some experiments. On the basis of the above works, this paper established the tectono- magmatic evolution framework of Liaonan metamorphic core complex. Firstly, we confirmed that the Liaonan metamorphic core complex is a typical Cordilleran metamorphic core complex, which is composed of three-layer structures and five parts. During the fieldwork and inside job, we studied the genetic relationship, positional connection, time dependence and exhumation history of Liaonan metamorphic core complex. Consequently, the evolution history can be subdivided into three stages. In the first stage (~130Ma), the detachment fault and ductile shear zone were formed by the regional extension. The Zhaotun pluton emplaced at depth of 25km, which suggested that the detachment fault and ductile shear zone developed at this depth. During the second stage (130~120Ma), the active emplacement of synkinematic granitic plutons influenced the development of detachment fault. We suggest that the corrugation was affected by the fracture properties of rocks in an extensional setting. Moreover, late kinematic emplacement of granitic plutons have also contributed to the development of corrugation of the Jinzhou detachement fault. At the same time (124Ma), the tectono-magmatic activity reached the peak value. The pluton which emplaced at the 124Ma intruded at the depth of 20km; The third stage (113～Ma), granitic intrusions emplaced at the lower plate of detachment fault which had ceased movement. This intrusion emplaced the position less than 3km. We consider that the Liaonan metamorphic core complex experienced a quickly exhumation history, and the rate of exhumation was about 1.55km/Ma. We considered that the emplacement of post-extensional Zhaofang pluton (113Ma), marks the termination of a series of tectono-magmatic activities during regional extension. After 113Ma, the Liaonan mcc, and the North China Craton experienced a regional uplifting and cooling. The tecton-magamtic evolution of Liaonan metamorphic core complex provide evidences for the extension and lithosphere thinning of North China Craton in late Mesozoic.