line-level: 2" class=MsoNormal>Geochronology of Youshan and Pingtian Granites in
In this study, the authors present LA-ICP-MS U-Pb zircon dating results which show that the ages of the Youshan granite and the northwestern part of the Pingtian granite are(213.4±3.0)Ma and(238.8±2.2)Ma, respectively. These results indicate that the Youshan granite was formed by the Indosinian magmatism and the Pingtian granite is probably a composite granite batholith formed in the Indosinian and Yanshanian periods. Some of the zircons from the Youshan granite display dark rims(in CL images)with Yanshanian ages, which suggests that the granite was probably affected by hydrothermal fluids during the Yanshanian period. Narrow dark rims of zircons are also observed in the Pingtian granite, suggesting effect of hydrothermal fluids.