| 安徽沙溪斑岩铜矿床成矿流体演化及分布规律 |
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| 引用本文：.1996.Evolution and distribution of hydrothermal fluids in the Shaxi porphyry copper deposit, Anhui Province[J].Mineral Deposits,15(1):23~33 |
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| 基金项目:国家自然科学基金资助项目 |
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| 中文摘要:对安徽沙溪斑岩铜矿床流体包裹体进行了详细研究，得到气液包裹体的均一化温度为100~500℃，盐度为2.0 wt%～60 wt%NaCl，并且流体包裹体的成分和温度随时间、空间变化而呈现出一定的变化规律。对热液脉石英及其流体包裹体中H2O、CO2的氧、氢、碳同位素组成分别进行了测定，得到热液δ18OSMOW为+3.51‰～+5.52‰，δDSMOW为-60‰～- 82‰，占δ13CPDB为-3.61‰～-6.53‰，表明成矿流体具有较为典型的岩浆热液特征。对沸腾包裹体的产出和特征进行了分析，为探讨矿床成因提供了证据。 |
| 中文关键词:流体包裹体 稳定同位素 沸腾作用 斑岩铜矿床 安徽沙溪 |
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| Evolution and distribution of hydrothermal fluids in the Shaxi porphyry copper deposit, Anhui Province |
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| Abstract:Investigations of fluid inclusions and stable isotopes were carried out for the Shaxi porphyry copper deposit, Anhui Province, and the results reveal a complicated variation in temperature and composition with respect to time and space. Microthermometry shows the temperature to be 450~340℃ for the potassic zone, 340～250℃ for the transitional zone, and 250～170℃ for the propylitic zone. Compositions and homogenization temperatures of fluid inclusions indicate that fluid pressure varies from 25 to 113 MPa, and salinities vary bimodally from 2 wt% to 20 wt% and from 40 wt% to 60 wt% respectively. In the saline halo diagram, there are two major high-salinity fluid-rich centers in concordance with mineralizing intrusives. Chemical compositions of fluid inclusions were determined by gas and ion chromatographic analysis. Components such as CO2, HCO3, Na+/ (Ca2++Mg2+), Ca2+ and SO42- vary systematically not only with mineralization phases but also with distance from disseminated mineralization. The coexistence of vapor- and liquid-rich or daughter mineral-bearing multiphase inclusions in vein quartz suggests that chalcopyrite-bearing anhydrite and quartz veins were formed in boiling low-salinity brines at 360 to 420℃. Coexistence of liquid-rich and vapor-rich inclusions which are homogenized at similar temperatures to liquid phase and vapor phase respectively indicates that boiling existed from the potassic core outward to the potassic-propylitic transitional zone. The fluid immiscibility in the Shaxi porphyry copper deposit may have played an important role in the mineralizing process. The chlorine- and alkali-rich fluid would have boiled due to a sudden decrease in pressure, resulting in the deposition of ore-forming substances and hence the formation of orebodies. Oxygen, hydrgen and carbon isotope studies on vein quartz and its fluid inclusions show that the ore-forrning fluids have δ18O of 3. 51 ‰ to 5. 52 ‰,δD of -60‰ to -82‰ and δ13C of -3.6‰ to -6.53‰. These data suggest a tnagmatic origin for the ore-forming fluids. However, the introduction of meteoric water must have also occurred at the last stage of ore deposition (δ18O= -4.71‰) . |
| keywords:fluid inclusions, stable isotopes, boiling process, porphyry deposit, Shaxi of Anhui |
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