SHRIMP U-Pb ages of zircons from Kailingjiao and Lichenjia granodiorites in western Zhejiang and their geological implications

Abstract：Mesozoic intrusive rocks are distributed in whole Zhejiang Province, mostly coexistent with volcanic rocks. Their ages can be divided into Early Yanshanian period and Late Yanshanian period in consistency with ages of volcanic rocks. However, recent researches on biostratigraphy and chronostratigraphy show that the age of Late Jurassic–Cretaceous volcanic-sedimentary rocks should be changed to Cretaceous. The isotopic ages of the Mesozoic intrusive rocks are between 135 Ma and 85Ma. Therefore, the ages of Mesozoic intrusive rocks should be changed from Early and Late Yanshanian period to Late Yanshanian period. The authors conducted zircon SHRIMP U-Pb dating of Kailingjiao and Lichenjia granodiorite closely related to the metallic ore resources in western Zhejiang. Weighted average ages of （151±3） Ma（MSWD＝0.74） and （148±2.4）Ma（MSWD＝1.2）are interpreted as the formation time of the granodiorite, suggesting the existence of Late Jurassic intrusive rocks in western Zhejiang. This period is also important for mineralization.