Characteristics of Geology, Fluid Inclusions and Stable Isotope of Wafang Pb-Zn Deposit in Henan

Wafang Pb-Zn deposit is located in the Xiong'er-Waifang Mountains of the southern margin of the North China craton. The ore bodies are existed in the upper Jidanping Formation of Xiong'er Group, and the ore minerals are pyrite, galena, sphalerite and little chalcopyrite, limonite, and hematite. The hydrothermal ore-forming processes are divided into three stages: quartz-pyrite stage (early stage), quartz-polymetal stage (middle stage), and quartz-carbonate vein stage (late stage). The fluid inclusions in quartz and calcite of ores are NaCl-H₂O two-phase, NaCl-CO₂-H₂O three-phase, and pure gas. The homogeneous temperatures the two-phase inclusions in the three stages are 150-260℃, 150-230℃ and 110-160℃, respectively. The average salinity w(NaCl) in the three stages are 12.22%, 8.55%, 6.29%, respectively. The δ¹³C_VPDB and δ¹⁸O_SMOW of the calcites of the middle stage are high with the mean of -7.34‰ and 15.56‰, respectively, showing the characteristics of freshwater carbonate. The δ¹³C_VPDB and δ¹⁸O_SMOW of the late stage are at an average of -3.05‰ and 2.21‰, respectively. The δ³⁴S values of sulfides in the early and middle stages are 2.747‰-7.737‰ and -11.187‰-7.286‰, respectively. We conclude that the ore-forming fluid in the early and middle stages was metamorphic fluid, which was related to the metamorphic dehydration of the Meso-Neoproterozoic slab subduction during Mesozoic continental collision between Yangtze and North China craton, then mixed with meteoric water in the late stage. The S isotope indicates that sulfur was derived from Meso-Neoproterozoic sedimentary stratigraphy by the reduction of marine sulfate. In the middle and late stages, negative δ³⁴S values occurred due to the mixing with meteoric waters. The characteristics of geology and ore-forming fluid in Wafang Pb-Zn deposit are similar to orogenic deposits.