| Abstract: | Abstract The Qinghai- Xizang (Tibet) Plateau and the “Sanjiang” area2, where are extensively developed the Tethys-type marine Triassic sequences with Indosinian tectonic disturbance and magmatism, provide an important region for the study of the tectonic evolution and the Indosinian movement of China as well as for the study of the boundary between Gondwana and Laurasia and the characteristics of the time-space distribution of the Tethys oceanic crust within the territory of China. Over a long period of time in the past, quite a number of scholars made substantial studies and discussions from various viewpoints on the geotectonic and regional geological evolution of this region. Based on some new data obtained recently and the field observations by the author, and by using the plate tectonic theory, the author considers that there developed a Pacific-type (active type) ancient continental margin bordering the Palaeo-Tethys ocean (or North Tethys ocean) in the south in Late Permian to Triassic times in the region of south-central Qinghai, northeastern Xizang (Tibet), western and southwestern Sichuan, and western Yunnan. Its characteristics basically represent the Indosinian tectonic evolution of this region. |
