THE TERRANES MOTION IN WESTERN CHINA: PALEOMAGNETIC EVIDENCES AND THEIR PROBLEMS

The geological evidences indicate that the terranes in Western China have been accreted by the Cretaceous. However, there is a great discrepancy in the paleomagnetic results of these terranes and Eurasia. The most plausible interpretation is that the collision between India and Eurasian, which started around the boundary of Cretaceous and Tertiary (about 65 Ma), resulted in the crustal shortening among the tectonic units. Based on the paleomagnetic results of the terranes in Western China, the amount of the crustal shortening between each terrane and Eurasia are calculated. The crustal shortenings between Eurasia and Junggar, Tarim, northern Lasha and southern Lasha are 655 km, 1 043 km, 1 265 km and 1 631 km, respectively. The paleomagnetic results of Tarim and Qaidam indicate that Altyn Taugh fault has experienced complicated tectonic activity. The shallow inclination phenomenon which have been observed in many paleomagnetic studies in Asia may be induced by the existence of long-term non-dipole field in the Tertiary.