清原南口前一带金矿床稳定同位素研究

STUDIES ON STABLE ISOTOPES FROM GOLD DEPOSITS IN NANKOUQIAN AREA.QINGYUAN

南口前一带金矿床的稳定同位素研究表明,金矿成矿与太古宙花岗岩—绿岩带,南口前花岗岩体关系密切。依据金矿床硫、碳同位素组成判定金矿床属热液成因,热液体系处于 H_(?)S 占优势的化学环境。在成矿过程中成矿介质由弱酸性向酸性,再向碱性方向演化;氧逸度随着成矿介质温度降低,金属硫化物的沉淀而逐渐升高。氢、氧同位素组成显示了岩浆热液有天水混入。铅同位素组成表明金矿中的铅属古老正常铅,与花岗岩中长石铅为同源。据此,作者认为南口前一带金矿属再平衡岩浆热液矿床。

Studies on stable isotopes in gold deposits in Nankouqian area show that the ge-neses of the gold deposits are closely related to the Archean granite-greenstone belt.The gold deposits are thought to belong to hydrothermal genesis based on S and Cisotope composition in the gold deposits.The hydrothermal system was in H_2S—superior chemical circumstances.During mineralization process,the pH value of mine-ralization liquor evolved from lower acidity to acidity and then to alkalinity,thefugality gradually increased with decreasing temperature and precipitating metallicsulfides,H and O isotope composition shows that magmatic solution was mixed upwith rain water.Lead isotope composition explains that the lead in gold depositsbelonged to ancient common lead and was the same source product with lead in felds(?)par from the granite.All above,gold deposits in Nankouqian area are considered to be re-equilibriummagmatic solution deposits.