Geochronology of the volcanic rocks in the Lu-Zong basin and its significance

The Lu-Zong (Lujiang-Zongyang) basin is one of the most important volcanic basins in the middle and lower reaches of the Yangtze River area, China. It comprises four shoshonitic volcanic units, which are, in an ascending order, the Longmenyuan, Zhuanqiao, Shuangmiao and Fushan Groups. The LA-ICP MS U-Pb zircon ages of the four units are: 134.8±1.8 Ma for the Longmenyuan Group, 134.1±1.6 Ma for the Zhuanqiao Group, 130.5±0.8 Ma for the Shuangmiao Group, and 127.1±1.2 Ma for the Fushan Group. The results indicate that all volcanic rocks in the Lu-Zong basin were formed in the Early Cretaceous from about 135 Ma to 127 Ma, lasting 8–10 Ma. There were no Jurassic volcanic activities in all the volcanic basins including the Lu-Zong basin in the middle and lower reaches of the Yangtze River area. This work has provided new chronological results for the further study and understanding of the tectonic, magmatic and metallogenic processes of eastern China in the Mesozoic. Supported by the National Basic Research Program of China (Grant No. 2007CB411405), the National Natural Science Foundation of China (Grant No. 40672062), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20050359013), the Scientific Research Project of CODES, Centre of Excellence in Ore Deposits, University of Tasmania (Grant No. CODES2006N2.3), the Anhui Public Geologic Projects (Grant No. 2005-48, 2007-1), and the Anhui Provincial Science Foundation for Distinguished Young Scholars (Grant Nos. 08040106907, 04045063)