A New SHRIMP Age of the Xiamaling Formation in the North China Plate and Its Geological Significance

<正>Setting up the hypostratotype of late Precambrian is the main aim of the research on the Meso-and Neoproterozoic in North China.The chronostratigraphic position is the key in this study. However,many key horizons have not been calibrated with the high-quality isotopic ages.Using the reported new U-Pb age with the Sensitive High-Resolution Ion Microprobe（SHRIMPⅡ）,a zircon U- Pb age was obtained of the ash bed in the Xiamaling Formation in North China Plate,yielding a weighted mean 206Pb/238U age of 1368±12 Ma.It is the first SHRIMP U-Pb age from the Xiamaling Formation in the North China Plate,and represents the depositing time of the middle part of the Xiamaling Formation.The zircon age plays an important role to understanding geological evolution of the North China Plate during Meso-and Neoproterozoic.