【摘要】 氯有两个稳定同位素35Cl和37Cl,在自然界中的丰度分别为75.53%和24.47%.氯同位素的分析方法主要包括气体同位素质谱法和热电离质谱法,目前的分析精度可达0.2‰.氯同位素组成用δ37Cl表示,它在自然界的变化可达15‰以上(-8.0‰~7.5‰).氯是上地壳流体中主要的阴离子,在矿物岩石和矿床的形成过程中起着重要的作用,因此研究自然界中氯的分布和运移对于地球科学各个研究领域而言有着重要的意义.目前,氯同位素在大气气溶胶、洋中脊玄武岩、壳幔物质循环过程、热液成矿作用及示踪卤水起源和演化等方面的研究中取得了许多新的重要进展.更多还原

【Abstract】 Chlorine has two stable isotopes, ~ 35 Cl and ~ 37 Cl,with their natural abundance of 75.53% and 24.47%, respecticely.Their large relative mass difference suggests that these isotopes should fractionate during reactions between aqueous chloride solutions and solid phases in which Cl is at least partly bonded. Two high-precision methods of determining chlorine isotopes have been developed in recent years: EIMS method and TIMS method, the measurement precisions of them are around 0.2‰. However, EIMS method requires relatively large quantities of chlorine (>1 mg Cl), precluding the investigation of materials with trace quantities or materials in limited supply. In contrast, TIMS method is both precise and sensitive allowing the analysis of microgram quantities of chlorine. Large fractionation of Cl isotopes occurs in nature with δ~ 37 Cl variation about 15‰(-8.0‰ ~ 7.5‰). Cl isotopic composition in the modern oceanic water is uniform, so seawater was suggested as the Cl isotope standard, SMOC. The river water show a large δ~ 37 Cl variations 0.74‰ ~ 2.85‰, the groundwater displays a δ~ 37 Cl variation of -0.5‰ ~ 0.69‰, δ~ 37 Cl of the salt lake fluids vary from -2.06‰ ~ 1.01‰. Mid-ocean ridge basalts(MORB)have a large δ~ 37 Cl variation of 3.2‰ ~ 7.2‰, whereas the granites show very small δ~ 37 Cl variations of -0.3‰ ~ 0.11‰. The carbonatites have δ~ 37 Cl ratios between-0.8‰ and 0.1‰. Halites have δ~ 37 Cl values of -0.6‰ ~ 1.2‰. The large δ~ 37 Cl variations in nature have made Cl isotope composition a very sensitive geochemical tracer with its major applications in the following fields:(1)atmospheric aerosol;(2)mid-ocean ridge basalt;(3)crust-mantle evolution;(4)hydrothermal mineralization;(5)origin and evolution of brines.更多还原