Study on the reconstruction of the paleo-tectonic stress field and its evolution in the Jinchuan mining district, Gansu Province, China

The Jinchuan mining district has undergone a complex tectonic evolution history, and detailed analysis of the post-mineralization deformation characteristics and stress field evolution stages needs to be completed. This paper employs structural analysis methods to stage and correlate the faults in the bedrock of the Jinchuan mining district, determining the structural deformation sequence. It identifies four significant fault combinations in the region, including NE-trending thrust faults and NW-trending strike-slip faults, NE-trending strike-slip faults and NW-trending thrust faults, NW-trending normal faults, and NEE-trending strike-slip faults. The paleo-tectonic stress field of fault is reconstructed by using the lower hemisphere stereographic projection method on the base of studying faults and striations. Combining the paleo-tectonic stress field results with the regional tectonic evolution history, the study accurately defines the stress field evolution stages in the Jinchuan mining district after the mineralization period, which is crucial for understanding regional tectonic evolution and the development of new prospective areas. The results indicate that the Jinchuan mining district experienced four phases of paleo-tectonic stress field after the mineralization period, characterized by multi-stage compression or extension in different directions. These phases responds to a series of regional tectonic thermal events since the Mesozoic respectively: Phase I exhibits a NW–SE compression stress field during the early to middle Jurassic (J1-2); Phase II shows a NE–SW compression stress field during the late Jurassic (J3); Phase III reflects a NE–SW extensional stress field during the Early Cretaceous (K1); Phase IV represents a NE–SW compression stress field since the Late Cretaceous (K2)