陕西谭家沟热水沉积型金矿床地质特征与成因分析

GEOLOGICAL CHARACTERISTICS AND GENESIS OF HYDRUTHERMAL SEDIMENTARY GOLD DEPOSIT IN TANJIAGOU SHAANXI

谭家沟金矿产于中泥盆统热水沉积岩中。矿体位于铁白云石硅质岩构造角砾带 ,是以浸染状矿化为主 ,由热水沉积铁白云石硅质岩提供矿质并基本在层内富集成矿的热水沉积改造型金矿床。铅同位素特征表明成矿金属来源于地壳 ;硫同位素组成特征表明硫主要来自海水硫酸盐的还原硫 ;氢氧同位素测试数据表明 ,成矿流体主要为原生建造水。成矿流体为SO4 2 F/Na+ Ca2 + 型 ,成矿物理化学条件为弱中等还原环境 ,成矿温度 15 0～ 170℃ ,盐度w(NaCl)为 6 .86 %。

The Tanjiagou Au deposit has Middle Devonian hydrothermal sedimentary rocks as host rock and ore bodies were situated in structure breccia zone of the foroan dolomite silicalite. All ore veins are confined to the strike fault. It is simple that the metallic mineral assemblage were formed in the mineralizing procecess. The hydrogen and oxygen isotope data of fluid inclusions in quartz veins indicate that ore forming fluid were mainly composed of the hydrothermal brine in deep seated rock, sulfur isotope composition of sulfides from ore veins suggest that the sulfur came from the reduction of sea water sulfate. The characteristic of ore lead isotope indicates that ore forming metal came from the crust. Fluid inclusion in quartz from ore vein are composed of Na +, K +, Mg 2+ , Ca 2+ , Cl -, SO 4 2- , F -, with average salinity of 6.86 wt% equivalent NaCl.