Age assignment of the Moshishan Group volcanic rocks in the Lishui area, ZhejiangProvince

On the basis of regional geological survey and volcanic structure divisions, this study carried out U-Pb dating for zircons from some typical volcanic rocks of Moshishan Group to precisely determine the stratigraphic age of the Mesozoic Moshishan Group volcanic rocks in the Lishui area, Zhejiang Province. The result shows that the SHRIMP zircon U-Pb age and LA-ICP-MS zircon U-Pb weighted average age of rhyolitic crystal welded tuffs on the bottom of Dashuang Formation are 154.9±5.5Ma and 152.0±7.0Ma, respectively, indicating that the Dashuang Formation belongs tothe Kimmeridgian Stage of late Jurassic. SHRIMP zircon U-Pb dating yields an age of 131.6±2.7Ma for rhyolitic crystal welded tuffs of the Gaowu Formation andtwo weighted ages of 128.6±1.7Ma and 139.5±2.5Ma for the rhyolitic crystal welded tuffs of the Xishantou Formation from two volcanic apparatus. It can be inferred based on the study above that the Dashuang Formation should belong to LateJurassic while Gaowu, Xishantou, Chawan and Jiuliping Formations to Early Cretaceous.