Geological And Geochemical Characteristics Of The Gaozhuang Gold Deposit,South-western Henan

The Gaozhuang gold deposit was formed under the deformation environment after the collision of North China and Yangtze plates.Orebodies occur as quartz-polymetallic sulfide veins in the Erlangping group,filling in the brittle-ductile shear zone which parallel to the orogenic belt.Ore minerals mainly include pyrite,pyrrhotite,marcasite,chalcopyrite,sphalerite,native silver,native bismuth and tellurium bismuth minerals.And gangue minerals mainly include quartz and calcite.By electron probe analysis,metal sulfides such as pyrrhoyite,pyrite and chalcopyrite contain gold.Fluid inclusions assemblage(FIA) uniform temperature method was applied to test the fluid inclusion characteristics.The samples contain three different types of fluid inclusions,including CO₂–H₂O three phases inclusions,CO₂inclusions and aqueous inclusions.In which CO₂–H₂O three phases inclusions are dominant,the total homogenization temperature varies from 284? to 349?and the salinities vary from 0.41 wt.%Na Cl.eqv to 4.14 wt.%Na Cl.eqv.According to the analysis of the CO₂–H₂O three phases inclusions,we estimated that the ore-forming fluid density range from 0.788g/cm³ to 0.874g/cm³;the trapping pressure could be 130MPa?160Mpa,corresponding to ore-forming depth of 4.8Km?5.9Km.The characteristic of the ore-forming fluid are medium temperature,rich CO₂ and low salinity.CO₂–H₂O three phases inclusions and aqueous inclusions with similar total homogenization temperature could be found in the same horizon,which implying the presence of fluids immiscibility.Hydrogen and oxygen isotope show that ?D_H2O(‰)=–83.4‰?–76.3‰,?¹⁸O_H2O(‰)=5.8‰?7.1‰,show that ore-forming fluid mainly from magmatic water.The?³⁴S _V-CDT of metal sulfides are from-3.0‰to-1.5‰.²⁰⁶Pb/²⁰⁴Pb of pyrrhotite ranges from17.106 to 17.505,²⁰⁷Pb/²⁰⁴Pb from 15.469 to 15.602,²⁰⁸Pb/²⁰⁴Pb from 37.835 to 38.194.The REE Distribution Curve of pyrrhotite is similar to the surrounding rock.Re-Os dating isochron age of pyrrhotite is the 137±2 Ma(MSWD=0.30).Based on the above studies and combined with the regional tectonic background,the Gaozhuang gold deposit is the medium temperature magmatic hydrothermal gold deposits.