THE APPARENT POLAR WANDER PATH FOR THE NORTH CHINA BLOCK SINCE THE JURASSIC

A palaeomagnetic study was carried out on sedimentary rocks from Datong, Shanxi Province, and on volcanic rocks from Chifeng, Inner Mongolia and Zhangjiakou, Hebei Province, China. All of these sites belong to the stable part of the North China Block (NCB). After detailed demagnetization experiments, reliable palaeomagnetic directions were obtained for middle Jurassic, late Cretaceous, and late Teritiary. These data define the apparent polar wander path for the NCB since the Jurassic, free from the possible effect of the movement along Tanlu fault since the Mesozoic. Comparisons with reliable palaeomagnetic poles obtained in Siberia and South China indicate that the middle Jurassic poles for North and South China are almost the same, while the Siberian pole is displaced from them to the west by about 18-degrees +/- 13-degrees. On the other hand, the Cretaceous poles for the three areas are not significantly different from each other. Consequently, it is suggested that the amalgamation of North China and South China was almost complete in the middle Jurassic, and that their accretion to Siberia continued until the late Cretaceous.