The Tengchong area, situated in southwest China, is an important field workshop to study the continental dynamics and the collision effects between the India and Eurasia plates. There are three stages of strike-slip shearing movements during the Cenozoic. The early Binglangjiang River transpressional shear zone is a left lateral strike-slip fault. The ages of the syntectonic dykes yield about 54—56Ma that is the same as the age of collision between the India and Eurasia plates. Although now the transpressional shearing zone trends south to north, when the fault occurred, it must extend in west east direction according to the direction of the movement of India plate. It can be concluded that the western boundary of the Tengchong block trends south to north is the result of the block clockwise rotation and used to be in west-east direction at the beginning of Cenozoic era. The second stage is characterized by dextral strike-slip shearing deformation about 19—24Ma and 11—14Ma determined by mineral K-Ar method. On one hand, the Gaoligong fault, together with the Nabang fault, is the west boundary of the extrusion Indochina block during the collision of two plates and the uplift of Tibet instead of Sagaing fault in the central Burma. On the other hand, because of the India plate moved northwords, the Gaoligong and Nabang faults, the same as the Sagaing fault, are also the response to the opening of Andeman Sea. The third stage have being occurred since 5—8Ma B.P. The structural stress field changed rapidly to be left lateral shearing instead of dextral shearing. The basins, formed during Oligocene due to the dextral shearing movement, stopped their evolution with the strata folded. The new stretch basins formed and the famous Tengchong lavas erupted and the steep normal fault formed responding to the crust uplifting. All evidences show that the Tengchong block extrudes southword and rotates clockwise, in the meantime an mantle upwelling take the place of the low lithosphere due to the delamination. We can rebuild up the movement pattern as following. During the subduction and collision between two continents, responding to the oblique stress, there occurred the Binglangjiang transpressional fault as an example. A rapid clockwise rotation of all blocks and shearing zones developped between about 55 and 24 Ma B.P., followed by the extrusion of the Indochina block from 24 to 19 Ma B.P. The movement of Gaoligong and Nabang faults during 11—15 Ma is the result of the opening of Andeman Sea. About 5—8 Ma B.P., the Tengchong block began to extrude southwords and rotate clockwise.
Ji Jianqing,Zhong Dalai,Zhang Liansheng. KINEMATICS AND DATING OF CENOZOIC STRIKE-SLIP FAULTS IN THE TENGCHONG AREA, WEST YUNNAN: IMPLICATIONS FOR THE BLOCK MOVEMENT IN THE SOUTHEASTERN TIBET PLATEAU[J]. Chinese Journal of Geology, 2000, (3): 336-349.