Analytical Method of Oxygen Isotope Compositions in Sulphates
Analytical Method of Oxygen Isotope Compositions in Sulphates
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发表时间：
2006
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通讯作者：
Wang De-fang
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作者：
Wang De-fang
硫酸盐是表生和内生地质环境中常见的矿物。它们是少数几种表现出氧同位素不依赖质量分馏的矿物之一。硫酸盐的氧同位素组成和非质量分馏可以提供有用的信息，其形成条件，揭示特殊的过程，不能通过元素浓度或单一的同位素比值测量。这是目前国际上同位素地球化学研究的前沿和热点。由于硫酸盐中氧同位素分析技术复杂，国内至今尚未建立该方法。本文介绍了本实验室新近建立的BaSO_ 4氧同位素的BrF_ 5同位素测定方法.本文介绍了从含硫酸盐样品中分离提纯硫酸钡的方法。介绍了BrF_ 5实验装置、试剂BrF_ 5的提纯技术、硫酸盐萃取制备O_ 2及氧同位素测定。对国际标准BaSO_ 4（NBS-127）和化学试剂BaSO_ 4的氧同位素组成进行了重复测定。NBS-127的δ 18 O_ V-SMOW值为9.20± 0.11‰，与已公布的标准值一致。化学试剂BaSO_ 4的δ 18 O_ V-SMOW值为14.64±0.13‰。BaSO_ 4氧同位素比值的分析精度可达0.13‰（1σ），优于Wasserman（1992）报道的0.15~0.29‰（1σ）。
Sulfates are a sort of ordinary minerals in the supergene and endogenetic geological environment. They are among the few minerals that show mass independent fractionation of oxygen isotopes. The oxygen isotopic compositions and mass independent fractionation of sulfates can provide useful information for their formation conditions, reveal special processes that can not be acquired by element concentration or single isotope ratio measurements. This is a frontier and hot topic for isotope geochemistry study in the world. Because analytical techniques of oxygen isotopes in sulfates are very complicated, this method was not established until now in China. A traditional BrF_ 5 fluorination method for oxygen isotope measurement of BaSO_ 4 was established recently in our lab. The separation and purification processes for BaSO_ 4 from sulfate-bearing samples are described in this paper. The BrF_ 5 experimental equipment, purification technique of reagent BrF_ 5, O_ 2 extraction preparation from sulfates and oxygen isotope measurement are introduced. The oxygen isotope compositions of an international standard of BaSO_ 4 NBS-127, and a chemical reagent of BaSO_ 4 were repeatedly measured. The δ 18O_ V-SMOW values of NBS-127 are 9.20± 0.11‰ , which is the same as the published standard values. The δ 18O_ V-SMOW values of the chemical reagent BaSO_ 4 are 14.64±0.13‰. The analysis precision of oxygen isotope ratios of BaSO_ 4 is up to 0.13‰ (1σ), and better than 0.15~0.29‰ (1σ)reported by Wasserman (1992).