RATIONALE Oxygen isotopic ratios are excellent tools to reconstruct paleotemperature and isotopic composition of the precipitating fluid. However, the measurement of the 17 O/16 O ratio is difficult due to the low abundance of 17 O. The present study reports a simplified high precision analytical technique for measuring the two oxygen isotope ratios in silicates. METHODS Silicate samples were ablated on-line by a CO2 laser in a BrF5 environment. The released oxygen (O2 ) was then cryogenically trapped in a molecular sieve zeolite (MSZ). Associated contaminants such as BrF5 , F2 , NF3 etc. were cleaned by passing the gas through a NaCl trap followed by a cooled (-25o C) MSZ-packed U-tube trap without using any conventional gas chromatographic column. The purified O2 was analysed by isotope ratio mass spectrometry for oxygen isotope ratios. RESULTS The ẟ17 O and ẟ18 O values of the working gas are calibrated by NBS-28 using values provided by Wostbrock et al17 and crosschecked by inter-laboratory reference UWG-2, SCO and IMAU-O2 . The average analytical precisions (using aliquots of NBS-28, UWG-2, SCO, and internal standards IIT-KGP-SQ quartz and IIT-KGP-NQ quartz) of ẟ17 O, ẟ18 O and ∆'17 O values are 0.04‰, 0.08‰ and 4 per meg, respectively. CONCLUSION A new cryogenic cleaning technique was developed that efficiently removes NF3 contaminants from oxygen gas produced by laser fluorination of silicates without using GC. The technique is simple, quick and cost-effective and provides highly precise and accurate ẟ17 O, ẟ18 O and ∆'17 O values.

中文翻译：

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一种高效分析硅酸盐中三重氧同位素的简单低温方法。

基本原理 氧同位素比率是重建沉淀流体的古温度和同位素组成的极好工具。然而，由于 17 O 的低丰度，难以测量 17 O/16 O 比率。本研究报告了一种简化的高精度分析技术，用于测量硅酸盐中的两种氧同位素比率。方法 硅酸盐样品在 BrF5 环境中通过 CO2 激光在线烧蚀。然后将释放的氧气 (O2) 低温捕获在分子筛沸石 (MSZ) 中。在不使用任何常规气相色谱柱的情况下，通过使气体通过 NaCl 捕集器，然后是冷却的 (-25o C) MSZ 填充 U 型管捕集器来清洁相关的污染物，例如 BrF5、F2、NF3 等。通过同位素比质谱法分析纯化的 O2 的氧同位素比。结果 NBS-28 使用 Wostbrock 等人提供的值校准了工作气体的 ẟ17 O 和 ẟ18 O 值，并通过实验室间参考 UWG-2、SCO 和 IMAU-O2 进行了交叉检查。ẟ17 O、ẟ18 O 和 ∆'17 O 值的平均分析精度（使用 NBS-28、UWG-2、SCO 和内标 IIT-KGP-SQ 石英和 IIT-KGP-NQ 石英的等分试样）为 0.04‰ , 0.08‰ 和 4 每兆, 分别。结论 开发了一种新的低温清洁技术，该技术可以有效地从硅酸盐激光氟化产生的氧气中去除 NF3 污染物，而无需使用 GC。该技术简单、快速且具有成本效益，并提供高精度和准确的ẟ17 O、ẟ18 O 和 Δ'17 O 值。