On the Time of Collision between the North China and Yangtze Continental Segments-the Principle and Application of lsotope Chronology
Li Shuguang(Department of Earth and Space Sciences of Vniversity of Science and Technology of China, Hefei 230026)
Isotope chronolgy can be used to determine the time of collision between continontal seg- ments by measuring the formation age of high pressure metamorphic rocks in the orogen and the age of metamorphism and deformation of the passive continental margin. Study has shown that eclogite, blue schist and high pressure gneiss of 245-209Ma in the Qingling-Dabieshan Qrogen were resulted from metamorphism of the subducted Yangtze crust and its lower lithospheric mantle. The Indosinian dy- namic metamorphism and magmatism were widely developed along the passive Yangtze continental margin. There was a lack of the record of Hercynian metamorphism and magmatism. All these suggest that the Yangtze continental segment collided with the North China during late Permian to early Trias- sic, then subducted I. A discussion is also made on the geology related to continental collision.