Abstract:The Songpan-Ganzi orogenic belt is an important part of northeastern Qinghai-Tibet Plateau. It is the major convergent region of North China block, Yangtze block and Qiangtang block. The orogenic belt consists of Mesozoic low-grade metamorphic strata and a series of magmatic rocks, and has recorded convergent events of the three blocks since Indosinian Period. Yajiang remnant basin within the orogenic belt, in which an extremely thick sedimentary series and wide spread magmatic rocks occur, is an ideal region for the research of tectonic evolution of Songpan-Ganzi orogenic belt. This paper conducts a research on detrital zircon LA-ICP-MA U-Pb geochronology. The results show that the zircon U-Pb age values focus on four peaks, 231-281Ma, 424-502 Ma, 707-983Ma, 1539-1850Ma, respectively, indicating that the west margin of Yangtze craton and Songpan-Ganzi orogenic belt have been subject to at least four stages of intensive tectonic-magmatic events, which were recorded in the Triassic strata in the area. The zircons with ages 231-281 Ma are most probably from the arc granites of east Kunlun Mountains, formed during subduction of Permian Songpan-Ganzi Ocean downward to North China block. The zircons with ages 424-502Ma derive from Yangtze block, representing a splicing event of south Qinling, north Qinling and North China block. The zircons with ages 722-983Ma are from the Yangtze block, and most probably from the granites of south Qinling formed during the subduction of Neoproterozoic extensional upper Yangtze craton basin below the North China block. The granites are the products of crust growth event in Jinning period. The ages 1539-1850 Ma correspond to that of basement of North China block, when east part and west part of North China craton collided in the central area and the North China paleo-continent was in the process of further solidification and extension. The Archean material and newly generated igneous and sedimentary rocks were inherited, and a great many of these detrital materials were carried into Songpan-Ganzi basin through an east-west direction transport system during the closure and collisional orogeny of south Qinling Ocean in Middle-Late Triassic Epoch. Our results suggest that origin of the Triassic Xinduqiao Formation of Songpan-Ganzi flysch basin was mainly the materials from east Kunlun Mountains, North China block and Qinling orogenic belt. The youngest detrital zircons can limit the oldest depositional age. The weighted average age of four youngest zircons is 241.8±4.5 Ma, temporally constraining the deposition event of sedimentary rocks.