Abstract: The Jinshajiang suture is one of the important sutures in eastern Tethys. The Yangla section of the Jinshajiang suture covers the east syntax of the Tibetan Plateau and is an important window for studying the collision-closing process of the Jinshajiang paleo-oceanic basin. Based on previous investigations and through field sampling and observation, combining with zircon SHRIMP U-Pb dating of granite intrusions, the authors completed the preliminary research on the collision-closure of the Jinshajiang paleo-oceanic basin. The results show that the emplacement ages of the intrusions in the Jinshanjiang basin are 246.1±3.5 Ma for Tongjige granodioprite in the south (a part of the Jiaren intrusion), 238.1±5.3 Ma, 239.0±5.7 Ma and 227.9±5.1 Ma respectively for Lunong, Linong and Jiangbian granodiorites in the middle, and 213.6±6.9 Ma for the Beiwu granodiorites in the north. Moreover, the collision-closure of the Jinshajiang paleo-oceanic basin progressed gradually from south to north with closure time ranging up to 33 Ma. The collision, however, occurred episodically and collision-closure mainly developed in four periods at around 246 Ma, 239 Ma, 228 Ma and 213 Ma, respectively. The diabases outcropped at Linongdagou as ~222 Ma diabasic dyke—close to the age of the Jiangbian granodiorite, suggesting that local tensional tectonic background occurred in the Jiangbian-Linong area at around 222 Ma.

Key words: Triassic, diachronous closure, Jinshajiang paleo-oceanic basin, tectonic implication, Yangla section