LA-ICP-MS zircon U-Pb ages and geological significance of the meta-intermediate-acidic volcanic rocks in Mangui area of Da Hinggan Mountains

Through the zircon U-Pb isotopes chronology research of the meta-intermediate-acidic volcanic rocks of Neoproterozoic-Lower Cambrian Dawangzi Formation in Mangui area of Da Hinggan Mountains, the authors explored the forming age and geological significance of the rocks. Dawangzi Formation is composed of meta-andesite, meta-dacite, rhyolite and a small amount of meta-crystalline tuff, and lacks interbeds of sedimentary rocks such as slate, metasandstone and schist. The authors determined the zircon U-Pb isotopes age of the meta-andesite, and the zircon 206Pb/238U weighted mean age is（199±1） Ma, indicating that the forming age of Dawangzi Formation meta-intermediate-acidic volcanic rocks is the early stage of Early Jurassic, not Neoproterozoic-Early Cambrian as in previous research. Early Jurassic volcanic rocks distributed in Erguna Block provide a provenance for Mohe Basin. Erguna Block was in the volcano-magmatic arc tectonic background in Early Jurassic. This research supplies new data for the geodynamics study during the closure of Mongolia-Okhotsk Ocean.