Geochronology and significance of volcanic rocks in the Ning-Wu Basin of China

The Ning-Wu (Nanjing-Wuhu) Basin is one of the most important volcanic basins in the Middle-Lower Yangtze River Valley, eastern China. It consists of four volcanic units, i.e., the Longwangshan, Dawangshan, Gushan, and Niangniangshan Formations. Their LA-ICP MS U-Pb zircon ages are 134.8 ± 1.8, 132.2 ± 1.6, 129.5 ± 0.8, and 126.8 ± 0.6 Ma, respectively. Results of this study indicate that all volcanic rocks in the Ning-Wu Basin were formed in the Early Cretaceous from 135 to 127 Ma, lasting 8-10 m.y. No Jurassic volcanic activities occurred in any of the volcanic basins of the Middle-Lower Yangtze River Valley, including the Ning-Wu Basin. These new chronological results provide significant evidence for further study of this region to improve our understanding of Mesozoic tectonic, magmatic, and metallogenic processes of eastern China.