Geochemical Characteristics and Tectonic Setting of the Ore-Bearing Granite Conglomerate of the Western Qinglong Uranium Ore Field in the Shigaizi Region and its Relationship with Uranium Mineralization

The Qinglong uranium ore field, including the Gangou and Panlingtou uranium deposits, is situated on the northern margin of the North China Craton (NCC). The Haifanggou Formation is a major uranium-bearing horizon in the ore field. We conducted petrographic, geochemical, electron probe, and highresolution scanning electron microscope studies aimed at analyzing granite conglomerate samples of the Shigaizi ore-bearing horizon, which is located in the western Qinglong uranium ore field. We determined the geodynamic evolution and mineralization of the region by comparing the Gangou and Panlingtou uranium deposits. Geochemically, the granite conglomerate has a high silica content (62.53 wt %-74.70% wt %) and is rich in alkalis (4.41-7.98 wt %) and Al2O3 (7.62-17.58 wt %) but poor in MgO (0.35-3.01 wt %) and CaO (0.17-1.80 wt %). It exhibits a weak negative Eu anomaly (0.81-1.12), is enriched in LREEs, Rb, Th, U, and K and severely depleted in Nb, Ta, Ti, and P, indicating that it is similar to I-type granite and has the characteristics of adakitic rocks. The main uranium mineral is pitchblende, which is associated with pyrite, organic matter (soot), and calcite. The Shigaizi ore-bearing horizon displays many similarities with the Gangou and Panlingtou uranium deposits. Common features include the whole-rock compositions and mineral chemistry. Based on these results and the evolution of the northern NCC, we suggest that the granite conglomerate formed in an active continental margin environment and have a great prospecting potential. The lack of deep prospecting may be the main reason why the concealed large and thick orebodies remain undiscovered.