摘要
许家坡 Ag-Au-Te 矿床产在中上元古界武当山群杨坪组副变质岩中.通过系统的地层含金、银性研究表明武当山群杨坪组为一有利于金银矿化产出的地层。稳定同位素(H、O、S、Pb)地球化学研究表明许家坡矿床成矿物质(Ag、Au)主要来自直接围岩,成矿流体为变质水和大气降水的混合物.矿床的成矿温度为175～290℃,成矿压力为40～70MPa,成矿流体的盐度为4.9～8.1%,氧逸度为10^(-41)～10^(-47),硫逸度为10^(-13)～10^(-15),成矿流体的化学组成类型为 Mg^(2+)-K^+-Na^+-Ca^(2+)-HCOr_3^--C1^--HS^-型,成矿物质 Au、Ag 主要以硫金(银)络合物形式迁移。
Xujiapo Ag-Au-Te deposit occurs within the parametamorphics of Yangping Forma- tion of Wudangshan Group of Middle-Upper Proterozoic Suberathem.By systematic stud- ies on Au-and Ag-bearing natures it is indicated that the Yangping Formation is a stratum favourable for Au-Ag mineralization.The studies on stable isotope(S,Pb,H and O) chemistry indicate that the minerogenic materials(Ag,Au,Te,S,Pb,etc.)of Xujiapo deposit are mainly derived from the immediate country rocks,and the minerogenic fluid is a mixture of metamorphic water with meteoric water.The minerogenic temperature of this deposit ranges from 175 to 290℃;minerogenic pressure,400—700 bar;salinity of minerogenic fluid,4.9—8.1%;oxygen fugacity,10^(-41)—10^(-47);sulfur fugacity,10^(-13) —10^(-15);the chemical composition type of the minerogenic fluid is:Mg^(2+)-K^+-Na^+ —Ca^(2+)-HCO_3^-—Cl^-—HS^-;the minerogenic materials of Au and Ag mainly migrate by the forms of the Complexes of thiogold and thiosilver.
