Objective‌ The northern Qaidam metallogenic belt is one of the most important gold and polymetallic metallogenic belts in Qinghai Province. The gold mineralization of the Xitieshan lead-zinc deposit, Qinglonggou gold deposit and Jinlonggou gold deposit, which have been discovered so far, is mainly produced in the ductile/brittle fault zone in the western Saishiteng area. In recent years, a new Sanjiaodingbei gold deposit has been discovered in the west part of Saishiteng tectonic belt. The detailed anatomical fracture characteristics and their relationship with gold enrichment are of great significance for prospecting and deployment in Saishiteng area.

Methods and Results Based on the detailed field investigation, structural analysis and microscopic characteristics of the Sanjiaodingbei fault zone, it is concluded that the ore-bearing fault zone has ductile deformation in the early stage and brittle deformation in the later stage. Among them, mylonitization and curved neck developed in the fault zone indicate that the early left-lateral ductile shear deformation was the main deformation. Later, brittle deformation was superimposed and fault cataclastic rocks developed, showing the characteristics of thrust faults.By means of quartz fabric analysis (EBSD) in mylonite belt, the results show that the preferred orientation of quartz C-axis lattice is dominated by bottom <a> slip, the formation temperature is medium and low temperature, and the extremely dense characteristics indicate that the deformation pattern is left-lateral shear.

Conclusion According to the comprehensive regional data, the mylonitization in the early stage and the superimposed brittle fracture in the late stage are the key factors of gold enrichment and mineralization, which can be used as a marker for further gold prospecting.