Structural analysis and ore-prospecting prediction of the Lujing uranium orefield in middle Zhuguangshan, South China

The middle Zhuguangshan area is one of the main uranium-producing areas in South China. The characteristics of structural deformations and ore-controlling structural regularity were studied in order to identify the features of uranium deposits and provide scientific guidance for ore-prospecting in blind ore deposits, with Lujing uranium orefield in middle Zhuaguangshan as the study objects. The authors revealed that NE-trending faults are ore-controlling and ore-hosting faults in Lujing area, as shown by field detailed observation and microscopic structure analyses. NE-trending faults have characteristics of multi-stage tectonic and hydrothermal activities belonging to shallow surface tectonic deformation. Geological phenomena show that NE-trending faults had at least three stages of tectonic events:compression deformation at the early stage (Late Jurassic-Early Cretaceous), tensional and torsion at the late stage (Early Cretaceous-Paleogene), and the faults changed into compress-shear faults at the late stage (Neogene). The uranium orebodies were developed in the NE-trending fracture zone, and the mechanical properties of NE-trending faults were tensional and transtensional during the major ore-forming stage. The near EW, NW and NS (NEE) trending faults were induced from the NE-trending main faults in the later right twisting deformation in Neogene period. The earlier uranium orebodies were reformed by the later tectonic deformation. On the other hand, some parts of the uranium orebodies were concentrated in the later faults. According to the characteristics of structure combination and ore-controlling regularity, the authors hold that the blind uranium orebodies which occurred as veins and lenses existent in the NE-trending fracture zone, and the secondary enrichment of uranium may exist in other direction faults.