Age assignment and geological significance of the ＂Budate Group＂ in the Hailar Basin

Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing＇an-Mongolian Orogenic Belt （XMOB）. Zircon U-Pb ages of eight volcanic rocks from the Budate Group and two basement granites in the Hailar Basin were reported in this study. The dating results indicated that the formation of these vol- canic rocks was consistent with the emplacement of Late Paleozoic basement granite in age （356-290 Ma）, i.e., Early Carbon- iferous to Early Permian rather than Early Mesozoic. Combined with regional geology, it was concluded that the Budate Group is the component of the basement of the Hailar Basin, and these volcanic rocks were formed at an active continental margin, which is related to the closure of the Hegen Mountains suture zone. The captured Neoproterozoic zircons （814-873 Ma） were probably derived from the Neoproterozoic basement materials in the Ergun Block, implying the close genetic relationships between the Ergun Block （including the Hailar Basin） and the Siberian Block.