西天山伊耳曼得型金矿流体特征及成矿环境

西天山一种以伊耳曼得和恰布坎卓它等金矿为代表的金矿类型,其成矿流体液相成分以K⁺离子为主,其次是Na⁺、Cl^-、SO₄^2-及少量的Ca²⁺、Mg²⁺.流体气相成分以H₂O为主,其次是CO₂、H₂,少量的O₂、N₂、CH₄和CO.流体的矿化度平均为8.28g/L,盐度比较低,其范围为1.5%~0.39%(NaCl),流体的pH值在2.8~5.5之间.流体离子强度为0.146~0.18.氧逸度为lgf o₂=-35.2~-38.9,流体的pH-lgf o₂稳定范围与冰长石-绢云母型和酸性硫酸盐型金矿床的稳定范围不一致.流体温度范围为93~151.4℃.流体压力范围为5.6~17 MPa.表明成矿流体具有低温、低压和低盐度的特点.流体属于H₂O-NaCl-CO₂体系,来自大气降水.大气降水渗滤到地下,受到火山和地温梯度的影响,形成了沿一定深度运动的热循环流体.成矿流体的物理化学环境是一种过渡类型.成矿流体沿火山碎屑岩孔隙和微裂隙多次渗透交代而成矿.

MINERALIZING ENVIRONMENT AND ORE-FORMING FLUID CHARACTERS OF YIERMANDE TYPE OF G-OLD DEPOSITS IN WESTERN TIANSHAN

The Yiermande deposit represents a type of gold deposits in Western Tianshan.The ore-forming fluid in Yiermande gold deposit can be divided into four stages.Study on the fluid inclusions shows that the ionic component in fluid is mainly K+,with minor Na+, Cl- and SO42-, and less Ca2+ and Mg2+.The gas phase is composed of mainly H2O, with minor CO2, H2, O2, N2, CH4 and CO. The ore-forming fluid exhibits 8.28 g/L in average degree of mineralization,with pH value ranging from 2.8 to 4.6, salinity from 1.5% to 0.35% (equal NaCl), ionic strength from 0.146 to 0.18, and lgfO2 value from -35.2 to -38.9. The stable area of lgf O2 - pH of Yiermande gold deposit is different from both that of the adularia-silicate type and that of acidic sulfate type.Its stable area of lgf O2 - pH is just in between the other two types.The mean temperature of fluid is from 93 to 151.4℃,while the pressure from 5.6 to 17 MPa.The fluid belongs to H2O-NaCl-CO2 system,mainly derived from meteoric water. The Yiermande gold deposit is supposed to be epithermal deposit.