Geology,Mineralogy,and Isotopic Characteristics of the Zhonghe Ag-Pb-Zn Deposit,Western Henan Province,Central China

Located in Luoning County,western Henan Province,Central China,the Zhonghe Ag-Pb-Zn ore field,is a newly discovered deposit in the Xiaoshan District.Ore bodies controlled by NNW Faults occur as veins within the Paleoproterozoic Xiong’er Group or the Early Cretaceous porphyritic granite.Given that the Zhonghe deposit has been covered by thick Quaternary sediments,the paragenetic mineral assemblage was determined mainly by microscopic observations,including the quartzsiderite-pyrite alteration (StageⅠ),polymetallic sulfide precipitation (StageⅡ),silver mineralization(Stage Ⅲ),and quartz-carbonate stage (StageⅣ).The host minerals for silver are diverse,such as freibergite,pyrargyrite,polybasite,argyrodite,canfieldite,argentite,and native silver,whereas those for Pb and Zn are galena and sphalerite,respectively.In order to constrain the ore-forming components of the Zhonghe deposit,a combined in-situ analysis was conducted on represented sulfides from StageⅡand Stage Ⅲ.In-situ δ^(34)S values of the analyzed sulfides,including the pyrite,chalcopyrite,sphalerite,and galena,display a relatively narrow range (0.90‰-5.0‰),which is close to magmatic sulfur source.The ^(206)Pb/^(204)Pb and^(207)Pb/^(204)Pb ratios show a narrow range (17.140-17.360 and 15.385-15.490),whereas the ^(208)Pb/^(204)Pb ratios exhibit a broad variation (36.601-37.943),indicating a contamination of the Xiong’er Group.Synthesis of geochronological and geochemical data from the Xiaoshan District,we contend that the ore-forming materials of the Zhonghe Ag-Pb-Zn deposit are originated from the lower crust,which has presumably been influenced by the large-scale lithospheric delamination of the eastern North China Craton during the Early Cretaceous.In consideration of the geological setting,mineralogy,and geochemical compositions,we suggest that the Zhonghe Ag-Pb-Zn deposit is characterized as intermediate sulfidation type epithermal deposit,and may be a potential exploration target for porphyry Mo-Cu deposits.