Structural controls on formation of the Xiayu vein-hosted Ag-Pb-Zn-Au orefield during intracontinental extension along the southern margin of the North China Craton

The Xiayu Ag-Pb-Zn-Au deposit, situated in the Early Cretaceous Xiong'er shan area on the southern edge of the North China Craton, comprises the Haopinggou, Shagou, Tieluping, and Houzhanggou deposits, making it the largest Ag producer in the southern North China Craton. Despite significant research efforts, the connection between extensional faults and vein-hosted Ag-Pb-Zn-Au deposits in this area is still not well understood. To address this issue, we introduce new structural data, fault-slip data analysis, and information on epithermal Ag-Pb-Zn-Au mineralization. Two separate paleo-stress inversion methods were applied to determine that the region was affected by two discrete stress fields: E-W transtension and NW-SE transtension. Our palaeostress reconstruction indicates that transtensional tectonics would have affected the emplacement of fault-fill veins (stage I) and extensional veins (stage II). Both types of geometric veins show two distinct stages of formation. The first stage (I) involves the development of quartz-pyrite within hydraulic breccia, transitioning into crack-seal laminated shear veins. These likely formed during a period of regional extension in an east-west direction. The second stage (II) features the deposition of undeformed quartz-sphalerite-galena within pre-existing dilational sites near newly formed normal faults or stage I veins. This second stage likely occurred during a regional extension in a northwest-southeast direction.