Research on the characteristics of basement fold structure and SN-trending mineralization zone in the Yinkeng lead-zinc-silver orefield in Jiangxi

In order to explore the structural characteristics and prospecting potential of the Yinkeng lead-zinc-silver polymetallic orefield, the authors selected the basement folds in this area as the research area to conduct field investigation and indoor analysis and reveal the basement fold geometry and stress field characteristics. The focus was on the mineralization characteristics of SN-trending metasomatic filling quartz veins, which are developed in the longitudinal tension faults formed in the late stage of folding. Through the actual measurement of the fold axis trace and the attitudes of the two wings, the geometric characteristics were summarized as follows: the direction of the hub is NE→NNE→SN→NNW from north to south, the angle between wings ranges from 33°to 52°, and the fold type is the closed, steep and sharp prismatic fold. Through the fold analysis method and the joint statistical method, the principal stress directions of the basement folds from the Caledonian to the Yanshanian were EW→NWW→NNW→NEE. The basement strata were squeezed in the EW direction in the early stage to form an SN-trending structural belt and a large number of SN-trending fold cleavage belts. During the transition of the stress field, the stress on the formation changed from compression to tension, which promoted the formation of SN-trending longitudinal fractures in the fold cleavage zone, and provided space for later NS-trending mineralization.Through actual measurement and observation, it is the first time to discover mineralized quartz veins in nearly SN direction in the basement fold. This quartz vein filled the longitudinal and secondary transverse tension fractures in the section at the late stage of folding. Mineralization analysis shows that the quartz vein has high mineralization characteristics. The average values of lead and zinc in mineralized quartz veins are 0.133% and 0.190%, and the average values of gold and silver are 0.127 g/t and 15.33 g/t. Twelve new SN-trending veins were discovered on the surface of the Qiaozikeng mining area and the 60, 104, and 140 level of the Niuxingba mining area, indicating that this area has huge metallogenic potential.