Abstract: Fracture veins are a research hotspot in shale gas exploration and development, and they play a significant role in revealing paleotectonic movements, fluid burial, and reservoir evolution processes. The Weiyuan-Rongchang north area, as a key block for current shale gas development, still lacks clarity regarding the development characteristics and formation age of fracture veins in its deep shale formations, as well as their relationship with tectonic and sedimentary evolution. The genesis and geological significance of these features require further investigation. Therefore, this study took the vein minerals in the deep shale fractures of Longmaxi Formation in this area as the research object. Through petrographic observation, cathodoluminescence analysis, fluid inclusion homogenization temperature testing, laser Raman spectroscopy analysis, U-Pb dating, and major and trace element and rare earth element testing, the genesis and geological significance of the fracture veins were revealed. The results showed that the calcite veins in deep shale fractures of the Longmaxi Formation in the Weiyuan-Rongchang north area formed in an oxidizing environment with relatively low paleofluid temperature and shallow burial depth, and their fluid source was groundwater influenced by hydrothermal activity. The U-Pb dating results showed that the formation age of the calcite veins was about (245.2 ± 5.1)Ma. The homogeneous temperature of coeval aqueous inclusions was mainly concentrated at 130 to 150 ℃, corresponding to the first stage of fluid charging, indicating that the initial opening of fractures occurred earlier than the formation age of the vein (245.2 ± 5.1)Ma. The calcite veins in this stage reflected that the Longmaxi Formation shale was affected by tectonic activity, with fracture systems communicating with the external environment, but the overall scale was limited, and the shale gas preservation conditions were not significantly damaged.