Chronology of the volcanic rock intercalations within the flysch of the Songpan-Ganzi folded belt and its geological significance

Several intercalations of volcanic and pyroclastic rocks were firstly discovered within the flysch of the Songpan-Ganzi folded belt. Samples were taken in northwestern Songpan of Sichuan and southwestern Hezuo of Gansu. Using U-Pb isotope mea-surement of LA-ICP-MS, the authors conducted dating of four samples and obtained ages of 205.9±1.6Ma, 208.9±1.8Ma, 210.4±1.6Ma and 212.3±1.5Ma separately, precisely showing the late Norian-early Rhaetian age of the Late Triassic. These are the age representatives of volcanic eruptions during the flysch accumulation and indicate that the deposition might have not stopped until the early Rhaetian. The discovery of the dated volcanic rocks would benefit the stratigraphic classification and correlation of the Up-per Triassic flysch within the Songpan-Ganzi folded belt, and can provide evidence and age constraints for the collision and oroge-ny between blocks of South and North China.