豫西潭头金矿床流体特征、碲化物形成条件及其对金富集过程的制约OA

The Tantou deposit is located in the Xiong'ershan district,the southern margin of the North China Craton.Various types of tellurides are developed and closely associated with native gold.However,the characteristics of fluids,the telluride forming conditions and their constraints on gold enrichment remain unlcear.Based on the detailed division of metallogenic stages,the fluid properties,tellurides and native gold geochemical compositions analyzed in detail by microthermometry,H-O isotopes,scanning electron microscopy and electron probe microanalysis.Tantou gold deposit can be divided into four metallogenic stages:① K-feldspar-quartz stage;② quartz-pyrite stage;③ sulfide-telluride stage;④ quartz-carbonate stage.Gas-liquid inclusions are mainly developed in the quartz-pyrite stage.The homogenization temperatures for the quartz-pyrite stage and the sulfide-telluride stage are 275～363℃and 258～285℃,respectively,with salinities of 5.01%～9.32%NaCleqv and 5.62%～8.10%NaCleqv,densities of 0.68～0.84 g/cm3 and 0.71～0.86 g/cm3,pressures of 5.5～18.3 MPa and 4.1～6.5 MPa,and corresponding mineralization depths of 0.55～1.83 km and 0.41～0.65 km,respectively.Telluride are composed of petzite,sylvanite,stützite,empressite,hessite,altatite,lingbaoite,melonite,coloradoite and tellurium.Through the analysis of mineral assemblages and physical and chemical conditions,the formation conditions of quartz-pyrite stages are T=300℃,lgfO2=-36.8～-32.1,pH=3.7～5.7,lgfTe2=-18.0～-10.9,lgfS2=-11.6～-6.8,while that of sulfide-telluride stage are T=250℃,lgfO2=-37.5～-31.8,pH=3.9～5.9,lgfTe2=-12.9～-9.4,lgfS2=-14～-9.5.From the quartz-pyrite stage to the sulfide-telluride stage,as the ore-forming depth becomes shallower,the temperature and lgfS2 of the fluid decrease,while the lgfTe2 increases.The salinity,density,lgfO2,and pH remain essentially unchanged.The early stage(quartz-pyrite stage)mainly precipitated Te-Au-rich pyrite through water-rock reaction,and the late stage(sulfide-telluride stage)mainly formed a large amount of sulfide,telluride and natural gold through fluid mixing.The tellurides start forming a metallic melt,which continuously extracts Au elements from the fluid,leading to the co-enrichment and precipitation of tellurides and gold.