中文摘要:该矿床流体包裹体丰富，为2相气液、1相液体、少数含子晶多相和含液态CO2三相包裹体。包裹体液相中富Na+、Cl-和SO42-，气相中H2O占优势，CO2次之。属NaCl-H2O体系。包裹体同位素分析表明，成矿流体为岩浆水和大气降水的混合流体。在温度高于360～400℃的中性-弱酸性热流体中，Au和Cu的络合物呈迁移状态，在温度低的弱酸-酸性的较还原环境下，围岩产生广泛的石英-绢云母化，导致Au、Cu络合物分解，沉淀出大量Au和Cu。
Abstract:The Xiaoxinancha large-size gold-copper deposit is located inside northeast Hunchun County at the eastenmost end of Jilin Province, lying in Tumenjiang delta zone. The ore deposit occurs on the western limb of the nearly SW-trending Wudao syncline, with the host rocks being metamorphic rocks of the Lower Paleozoic Qinglongcun Group. Gold and copper mineralization are closely related to the concealed early Yanshanian granite porphyry in this area. The orebody consists of gold- and copper-bearing quartz veins which fill the NNW-trending fissures as well as veinlet-disseminated mineralized bodies on their both sides. Its total NNW-striking length is some 2.5 km, its width is 0.8 km, and the downward extension reaches 100~700 m. The ore deposit contains abundant fluid inclusions, which are mainly two phase gas-liquid and one phase liquid inclusions and, next, polyphase inclusions that contain daughter crystals, with a few two phase gas-rich inclusions and three phase inclusions that contain liquid CO2. The principal gold and copper mineralization stage is dominated by the first two types. The most striking character of the fluid composition is that in cations, Na+ is most numerous and in anions, Cl- is slightly more than SO42-. In gas phase, H2O is dominant, followed by CO2. Ore-forming fluids are basically of the NaCl-H2O system. δD values of inclusions vary in the range of -51‰～80‰, and δ18H2O in the range of +0.13‰～+5.61‰, falling into the region between the magmatic water and the meteoric water line. δ13CCO2 values of CO2 gas in inclusions are -0.5‰～-6.8‰, exhibiting character of deep carbon. All these data demonstrate that the ore-forming fluids are mixed fluids of magmatic hydrothermal solution derived from the depth and meteoric water. At the early stage of the ore-forming process, magmatic hydrothermal solution played a leading role. When temperature was higher than 500 ℃, fluids reacted with wall rocks at the top of the porphyry body and the contact zone nearby, resulting in such alterations as biotitization and K-feldspathization. Later, temperature got lower and lower, salinity increased to 40 wt%NaCl ~50 wt% NaCl, and the fluids changed from weakly alkaline to weakly acid-acid. Under the conditions of T 500~340℃ or so, fO2>10-25 Pa, fC02>107.3 Pa and relatively low Eh (＜-0.76), fluids interacted with wall rocks of the exocontact zone, leading to quaraz-sericitization and producing precipitates of pyrite and arsenopyrite. At that time, CuCl- and Au (HS) 2- were in the state of migration, with the precipitation of merely a small quantity of gold and copper minerals. In the middle ore-forming stage, the high-temperature and high-salinity hot fluids migrated to the near-surface area with well-developed fissures, where the percolation of large quantities of meteoric water and the convection and circulation between magmatic fluids and meteoric water took place, thus forming mixed fluids and changing original equilibrium of the fluid system. Under the condition of T 360~160℃ or so，salinity 3 wt%NaC1～15 wt%NaCl, fO2 10-28～l0-41 Pa, fCO2>106.5～l02.6 Pa, Eh - 0.7～0. 55 eV and pH 4.7～5.7, Wall rocks experienced more extensive quartz-sericitization, accompanied by the precipitation of copper and gold and hence the enrichment of gold and copper. At this stage, heated meteoric water played a key role in the ore-forming process. At the late ore-forming stage, more and more meteoric water was added, mixed fluids overflowed, and temperature dropped. When the temperature became lower than 160℃, large quantities of volatiles (such sa CO2) would be released, which caused the increase in concentration of fluids that had been diluted to some extent at the middle stage. Nevertheless, fO2 and fCO2 had decreased by that time, and fluids were weakly alkaline to alkaline; under the reduction with relatively high Eh value, the fluids only gave rise to carbonatization of wall rocks, and the ore-forming process drew to an end, basically with no precipitation of useful minerals.
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基金项目:国家自然科学基金资助项目(49070102)
引用文本：
李荫清，陈殿芬.1995.吉林小西南岔金铜矿床流体包裹体及成矿作用研究[J].矿床地质,14(2):150~173.1995.A study of fluid inclusions and ore-forming process of the Xiaoxinancha gold-copper deposit, Jilin Province[J].Mineral Deposits14(2):150~173
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