DOI:
矿床地质:2006,Vol.>>Issue(4):427-437

安徽铜陵狮子山铜(金)矿田成矿流体地球化学研究
中国地质科学院矿产资源研究所
Geochemistry of ore_forming fluids in Shizishan orefield, Tongling, Anhui Province
李进文,裴荣富,梅燕雄,朱和平,王莉娟,李铁军,王永磊
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中文摘要:为深化认识狮子山铜(金)矿田的成矿机制和规律,文章对该矿田的流体包裹体进行了观测和显微测温,结果表明,狮子山矿田铜(金)矿床与成矿有关的流体包裹体丰富,可以划分为富气相包裹体、富液相包裹体和含子晶(多为石盐,少量钾盐等)多相包裹体3种类型,其均一温度集中于131~570℃,盐度w(NaCleq) 1.07%~60.72%;流体包裹体气相成分以H2O为主,富含CO2和N2,普遍含有少量CH4、He、Ar、O2、C2H6、H2S等成分;阳离子主要是Na+、K+、Ca2+,阴离子成分主要为SO2-4和Cl-。含矿石英和石榴石的δ18OH2O值分别为0.38‰~10.7‰(均值5.49‰)和8.74‰~9.64‰(均值9.24‰),δD值分别为-94.3‰~-58.64‰(均值-71.50‰)和-95.77‰~-75.82‰(平均-85.25‰);热液成因方解石的δ13C值集中于-6.9‰~-4.3‰,不同于区内大理岩、灰岩、白云岩的δ13C值(0.1‰~5‰)。由此反映出,成矿流体源自岩浆流体,可近似地作为NaCl-H2O体系,属NaCl不饱和型,经历了从高温、高盐度向中温、中低盐度的持续演化过程,与成矿作用阶段基本对应。初始阶段的成矿流体呈超临界态,演化过程中有一定比例的大气降水或地下水的参与。降温、减压、流体沸腾是导致流体中巨量铜(金)元素卸载的主要因素。
Abstract:Shizishan is the largest copper (gold) orefield in the Tongling ore district which is dominated by skarn and stratabound skarn deposits and characterized by complex metallogenic processes. The hydrothermal mineralization can be divided into three stages, i.e., skarn, quartz_sulfide and carbonate_quartz_sulfide stages. Studies of fluid inclusions might provide useful clews for ore_forming mechanism and regularities. Based on observation and microthermometry of the fluid inclusions, the authors hold that these copper (gold) deposits are rich in fluid inclusions. According to the nature and the volume proportions of phases at room temperature, the fluid inclusions in garnet, quartz and calcite can be divided into three types, namely, gas_rich, liquid_rich and daughter mineral_bearing polyphase brine inclusions with homogenization temperatures of 131~570°C and salinities w(NaCleq)of 1.07%~60.72%. The daughter minerals are mainly halites, with minor sylvite and other minerals, suggesting that the ore_forming fluids belong approximately to the NaCl_H2O system and are of an unsaturated NaCl_type. The temperatures of homogenization and the salinities of the same type of inclusions gradually decrease in order of garnet→quartz→medium→coarse calcite. The dominant components of the vapor phase are H2O and rich CO2 and N2, together with small amounts of CH4, He, Ar, O2, C2H6 and H2S. The components of the liquid phase are mainly Na+, K+, Ca2+, SO2-4 and Cl-. The δ18OH2O values range from 0.38‰ to 10.7‰ (avg. 5.49‰) in quartz, and 8.74‰ to 9.64‰ (avg9.24‰) in garnet. The δD values range from -94.3‰ to -58.64‰ (avg. -71.50‰) in quartz, and -95.77‰ to -75.82‰ (avg. -85.25‰) in garnet. The δ13C values of hydrothermal calcite are clustered between -6.9‰ and -4.3‰, quite different from those (0.1 to 5‰) of local marble, limestone and dolostone. From these data, it can be concluded that the ore_forming fluids were derived from the magma and existed in a supercritical condition in their early stage, and experienced an evolution from high temperature and high salinity to moderate temperature and low-moderate salinity, corresponding well with the mineralization stages. There was the addition of meteoric water during the fluid evolution. Temperature decrease, decompression and boiling of the fluids were the main factors that led to the enrichment of large amounts of copper and gold.
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基金项目:国土资源部专项研究计划(20010103)和中国科学院地质与地球物理研究所矿产资源研究重点实验室资助
引用文本:
李进文,裴荣富,梅燕雄,朱和平,王莉娟,李铁军,王永磊.2006.安徽铜陵狮子山铜(金)矿田成矿流体地球化学研究[J].矿床地质,25(4):427~437
李进文,裴荣富,梅燕雄,朱和平,王莉娟,李铁军,王永磊.2006.Geochemistry of ore_forming fluids in Shizishan orefield, Tongling, Anhui Province[J].Mineral Deposits25(4):427~437
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