Abstract:The zircons of alkali- feldspar granite in Nuominhe area, Northern Da Hing’an Mountains are self- shaped—semi- self- shaped short column—plate- like, with a well- structured oscillation growth zone and a high Th/U ratio (1.10～2.18). It is a typical magma- forming zircon. The LA- ICP- MS U- Pb geochronology study showed that the rock was formed in the Early Carboniferous Duinian period (352.9 ± 3.3 Ma). Rock geochemical studies show that the rock belongs to quasi- aluminum- weak aluminous high- potassium- calcium- alkaline rock, rich in silicon (SiO 2 =73.25%～77.01%), alkali- rich (Na 2 O+K 2 O=7. 72% ～9.48%), rich Iron (Fe 2 O 3 =2.06%～2.97%, Fe 2 O 3 + FeO=2.32%～3.33%), magnesium deficiency (MgO=0.08%～0.26%). Strongly depleted Sr, Eu, Ba, Ti, P and other elements, the REE distribution curve is right- winged seagull type and obvious Eu negative anomaly ( δ Eu=0.26～0.31), and the rock is judged to be A- type granite. Lu- Hf isotope analysis based on zircon U- Pb isotopic dating.The sample 176 Yb/ 177 Hf value was 0.03778～0.133612, the 176 Lu/ 177 Hf value was 0.001095～0.004155, and the 176 Hf/ 177 Hf value was 0. 282824～0.282863. The corresponding zircon U- Pb age calculated zircon ε Hf ( t )=8. 9 ～10.6, the first- stage Hf mode age was t DM1 =560～658 Ma, and the two- stage Hf mode age t DM2 =815～974 Ma, indicating that it originated from Partial melting of the Neoproterozoic source rocks. Our study and the development of the Early Carboniferous A- type granite in the Erguna block indicate that the closure of the Paleo- Asian ocean basin in the northeastern part of the Xingmeng orogenic belt occurred in the Early Carboniferous. Combined with the closure of the Paleo- Asian Ocean basin in the central part of Inner Mongolia, it is the Late Carboniferous, indicating that the closure of the ancient Asian ocean basin is a “scissor- like” development process in the east, west and west.