Abstract:Diagenesis age of skarn is a difficult problem for the mineralization study of skarn deposit in the past decades. The U-Pb precise age of garnet in skarn dated by femtosecond laser erosion system with high-resolution inductively coupled plasma mass spectrometer, is 83.2±2.3Ma (MSWD=1.2, n=26), from Sangri copper deposit in Bangion county, Tibet. These data showed that Diagenesis age of skarn was late Cretaceous, effectively. At the same time, Compared with the U-Pb age of zircon from ore-bearing porphyry and the Re-Os age of molybdenite, U-Pb age of garnet was consistent with them within the error range, basically, indicating that they were the products of the same mineralization event. Therefore, the accurate U-Pb dating of garnet can effectively confirm the diagenesis age of skarn deposit or porphyry-skarn deposit. It’s a new geochronology method and provides useful support for the metallogenic mechanism study of skarn deposits, with a good application prospect.