内蒙古赤峰地区安家营子金矿成矿流体研究  

Ore -forming fluids of the Anjiayingzi gold deposit in Chifeng region,Inner Mongolia

作　　者：李永刚[1] 翟明国[1] 苗来成[1] 薛良伟 朱嘉伟 关鸿[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]河南省地质科学研究所,郑州450053

出　　处：《岩石学报》2004年第4期961-968,共8页Acta Petrologica Sinica

基　　金：中国科学院重大知识创新项目(编号:KZCX1-07)资助

摘　　要：该金矿床产于晚燕山期安家营子二长花岗岩岩体内,受NNE向断裂带控制。矿化类型属蚀变岩型。矿物包裹体研冤表明,成矿流体为CO2-H2O-NaCl-KCl体系,来自安家营子花岗岩浆期后热液,其氢氧同位素组成分别为δD=-80.0^-96.5‰,δ18OH2O=4.5~5.7‰。主成矿期四个成矿阶段包裹体的均一温度和盐度分别为Ⅰ=340~360℃:Ⅱ=315~330℃,3.80~6.20 wt％／NaCl,CO2密度0.2~0.3 g／cm3;Ⅲ=245~285℃,3.5~4.5 wt％NaCl:Ⅳ=150~170℃,<2.0wt％NaCl。成矿流体盐度和CO2密度均较低。包裹体气相成分中(CH4+CO)／CO2<0.1,成矿环境为弱还原条件;液相成分中K++Na+总量较高,K+>Na+有利于碱质交代成矿作用。根据CO2包裹体获得资料计算,成矿压力为500~750×105Pa,成矿深度为2.0~2.5 km。流体控矿因素有水-岩反应、CO2与H2O-NaCl溶液不混溶和硫浓度降低等。其中以水-岩反应为主,它贯穿成矿全过程,控制原始成矿流体由碱性向弱碱性-弱酸性变化,使流体发生交代成矿作用。Hosted within the late-Yanshanian Anjiayingzi monogranite, the Anjiayingzi gold deposit is controlled by NNE-trending faults and is characterized by altered-desseminated-type mineralization. Fluid inclusion investigations indicate that mineralizing fluid of the deposit is dominated by a CO2-H2O-NaCl-KCl system, with delta(D) and delta(18)O(H2O) ranging from -80.0 similar to -96.5 and 4.5 similar to 5.7parts per thousand, respectively, which is of a feature of magmatic source, probably from the Anjiayingzi granite. The gold mineralization can be subdivided into four stages, of which fluid inclusions have homogeneous temperatures of 340 similar to 360degreesC, 315 similar to 330degreesC, 245 similar to 285degreesC, and 150 similar to 170degreesC, respectively, with relatively lower CO2 densities and salinities of 3.80 similar to 6.20 wt%, 3.5 similar to 4.5 wt%,and < 2.0 wt%. Of the gaseous phases, the ratio of (CH4 + CO)/CO2 is less than 0.1, indicative of a weak deoxidization mineralizing condition, whereas among the liquid phases, K+ and Na+ contents are relatively high, with K+ > Na+, which is favorable to form alkalic metasomatic-type mineralization. According to data obtained from CO2-type inclusions, calculated mineralizing pressure is 500 similar to 750 x 10(5) Pa, equivalent to a depth of 2.0 similar to 2.5 km beneath the earth's surface. The gold mineralization was controlled by water-rock reaction, immiscibility of CO2 and H2O-NaCl solutions, and decrease of sulfur concentration. Of these, the water/rock reaction is the most important one, which probably occurred during the whole metallogenic process, controlling changing of the primary mineralizing fluid from weak acid to weak alkaline in composition, and led to metasomatic metallogeny.

关 键 词：流体包裹体 成矿作用 安家营子 赤峰地区 内蒙古 

分 类 号：P618.51[天文地球—矿床学]