Late Triassic-Cenozoic Thermochronology in the Southern Sanjiang Tethys, SW China, New Insights from Zircon Fission Track Analysis

The Sanjiang Tethys orogenic belt is located in the southeast side of the Qinghai-Tibet Plateau. It has undergone the opening and closing movements in different periods of Tethys oceans, complex accretive orogeny and strong mineralization from Paleozoic to Mesozoic. Using zircon fission track (ZFT) thermochronology, this study reveals the Sanjiang Tethys has experienced multi-stage tectonic activities during the Late Triassic-Cenozoic. The 15 ZFT ages with their decomposition components obtained from Sanjiang Tethysian region range from 212 to 19 Ma, which not only shows 6 age groups of 212, 179–172, 156–133, 121–96, 84–70 and 50–19 Ma, but also constrains the age limit of the tectonothermal events. These age groups recorded the Paleo-Tethys main and branches ocean opening/closure time. The age-elevation plot indicates the Sanjiang region had differential uplifting and exhumation and fast uplifting times of ca. 133, 116 and 80 Ma, coinciding with the age groups mentioned above. These results show new geochronological evidences and viewpoints.