Abstract:The zircons of alkali-long granites in the Nomin River area in the northern Daxinganling 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 (SiO2=73.25% ~ 77.01%), alkali-rich (Na2O+K2O=7.72% ~ 9.48%), rich Iron (Fe2O3 = 2.06% ~ 2.97%, Fe2O3 + 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 (δEu=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 176Yb/177Hf value was 0.03778 ~ 0.133612, the 176Lu/177Hf value was 0.001095 ~ 0.004155, and the 176Hf/177Hf value was 0.282824 ~ 0.282863. The corresponding zircon U-Pb age calculated zirconεHf(t) = 8.9 ~ 10.6, the first-stage Hf mode age was tDM1 = 560 ~ 658 Ma, and the two-stage Hf mode age tDM2 = 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.