Gyirong basin and its adjacent area are located at a special position in the Himalayan orogen, where the south Tibetan detachment system (STDS) and N-S trending rift converged. The north Himalayan orogen here can be divided into five petrologic-tectonic units successively from south to north: 1) the Greater Himalayan crystalline complex (GHC); 2) the STDS shear zone; 3) the Tethyan Himalayan sedimentary sequence (THS); 4) the late Cenozoic sedimentary basins, such as Gyirong and Oma basins; and 5) the Malashan gneiss dome. Structural studies show that this area experienced four stages of deformation: 1) the earlier south-directed thrusting, preserved both in the GHC and THS; 2) top-down-to-north slip along the STDS, normal faults related to this slip formed the early controlling structures of the Cenozoic basins，and the tilted pattern of the blocks between the basins indicated a north-directed slip; 3) east-west extension, the resultant N-S trending normal fault formed the eastern boundary of the basins; and 4) late gravitational collapse. Zircon SHRIMP U-Pb dating on the syn-deformational (leuco-) granite along the STDS indicates that the major activity of the STDS occurred at ca. 26 Ma, but its onset may have begun as early as ca. 36 Ma. south Tibetan detachment system (STDS), deformation stage, syn-deformational granite, zircon SHRIMP U-Pb dating, onset ageThe India-Asian collision and the related convergence resulted in the uplift of the Tibetan Plateau and the formation of the Himalayan orogen. Although the initial collision occurred at 65-55 Ma [1][2][3][4] , the main Himalayan orogeny began much later, and existing data concentrated on an onset age of early Miocene, about 25 Ma [5] . This orogeny formed the south Himalayan thrust system, which consists of, successively from north to south, the main central thrust (MCT), the main boundary thrust (MBT), and the main frontal thrust (MFT) [6][7][8][9] . When the south Himalaya underwent thrusting, the north Himalaya and south Tibet experienced widespread extension. Based on their occurrences and formation ages, the resultant extensional structures can be divided into three categories (Figure 1): 1) the south Tibetan detachment system (STDS) along the northern slop of the Himalayas, 2) the N-S trending rifts in the north Himalaya and south Tibet, and 3) the north Himalayan gneiss domes (NHGD). Such abundant structures were preserved in north Himalaya that are ideal for studying the spatial and temporal relationship among the different categories of structures, the tectonic evolution of these structures; and these studies are significant for revealing the formation and uplift of the Tibetan Plateau.Gyirong basin and its adjacent area lie in the Himalayan orogen, with geographic coordinates of 28°20′-29°00′N and 85°00′-85°30′E. Tectonically, this area is located between NHGD and MCT with the large shear
