热液中银、铅、锌共生分异的实验研究

AN EXPERIMENTAL STUDY ON PARAGENESIS AND SEPARATION OF SILVER,LEAD AND ZINC IN HYDROTHERMAL SOLUTIONS

对NaCl HCl H2 O体系中银、铅、锌氯络合物稳定性进行实验研究 ,结果表明 :热液中银、铅、锌氯络合物的稳定性受体系温度、pH、Eh以及组分浓度的控制。相同温度下 ,H+ 、Cl-浓度降低 ,还原硫增加 ,均使络合物趋于不稳定 ,发生不同程度的沉淀分异。当t=3 0 0℃ ,[Cl-]=0 .2 4mol/L,pH =6.86时 ,铅氯络合物的沉淀量达 5 5 % ,锌氯络合物的沉淀量超过 92 %。热液体系中硫化物的存在 ,对银的影响最大 ,溶液中的银氯络合物几乎沉淀完全 ,浓度可降至检测限以下。而铅和锌的氯络合物相对稳定。热力学计算表明 :溶液中的银是以硫化银或自然银的形式沉淀析出。因此 ,还原硫的存在是导致热液体系中银与铅锌发生分异的重要因素。

The mechanism of paragenesis and separation of Ag, Pb and Zn has been studied by means of experiments on the stabilities of their chloride complexes i n the NaCl HCl H 2O system. The experimental results show that the stabilitie s of silver , lead and zinc chloride complexes are affected by temperatu re, p H, Eh and the concentrations of components. Chloride complexes of silver, lead a nd zinc become unstable and ore precipitated in varied extents at the same tempe rature with decreasing [H +], [Cl -] and increasing reduced sulfur concent ration. At 300 ℃, [Cl -]=0 24 mol/L, pH=6 86, the precipitated fraction of lead chloride complex reaches up to 55%, and that of zinc chloride complex ex ceeds 92%. When the sulfides are added in hydrothermal solutions, the silver con centration of the solution will decrease dramatically, even to zero, while chlor ide complexes of lead and zinc keep stable. Thermodynamic calculation indicates that the silver chloride complex becomes unstable and silver is precipitated as Ag 2S or Ag. It is concluded that the presence of reduced sulfur will cause th e separation of silver from lead and zinc.