【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δ¹⁸O_SMOW为+3.51‰～+5.52‰,δ_DSMOW为—60‰～—82‰,δ¹³C_PDB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。更多还原

【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 113MPa, and salinities vary bimodally from 2wt% to 20wt% and from 40wt% to 60wt% 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 SO₄^2- 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 vaporrich 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-forming 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 magmatic 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‰).更多还原