GSR系列岩石标准物质的锂同位素组成及其作为质控基准的可靠性

Lithium Isotopic Composition of GSR Series Rock Reference Materials and Their Reliability as Quality Control Standards

  • 摘要: 岩石标准物质是国际实验室进行同位素数据比对和监控数据准确度和精确度的基准。近年来,国际通用的美国地质调查局(USGS)系列岩石标准物质面临价格攀升、库存短缺及获取周期长等问题,制约其在常规分析中的广泛应用。中国岩石标准物质长期缺乏高精度的锂同位素参考数据,未能在国际比对与日常质控中充分发挥作用。为推广国产标准物质应用、提供高可及性与更广岩性覆盖的质控基准,本文采用多接收电感耦合等离子体质谱(MC-ICP-MS)测定了16种国家岩石标准物质(GSR)的Li同位素组成。所选标准物质涵盖了从超基性到酸性的主要岩石类型,保证了数据体系的岩性代表性。结果显示,GSR系列标准物质的Li同位素组成(δ7Li)变化范围为−3.0‰至13.9‰,而USGS系列标样的δ7Li值范围为−0.1‰至7.0‰,GSR系列在岩性覆盖广度和同位素组成跨度上较USGS系列标样更具优势。与已发表文献数据对比证实,绝大多数GSR标样测定结果重现性优于0.5‰,均匀性良好。研究表明,GSR系列岩石标准物质具备作为实验室间锂同位素数据比对基准的可靠性与适用性,可作为USGS系列重要补充,为中国地球化学实验室提供稳定可及的国产质控选项,降低进口依赖,支撑锂同位素地质过程示踪研究。

     

    Abstract: Rock reference materials serve as benchmarks for inter-laboratory isotopic data comparison and for monitoring data accuracy and precision. In recent years, the internationally used United States Geological Survey (USGS) series rock reference materials have faced challenges including rising prices, inventory shortages, and long procurement lead times, limiting their widespread application in routine analyses. Chinese national rock reference materials have long lacked high-precision lithium isotopic reference data, preventing them from fully playing a role in international comparisons and daily quality control. To promote the application of reference materials and provide quality control benchmarks with higher accessibility and broader lithological coverage, this study employed multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) to determine the Li isotopic compositions of 16 national rock reference materials (GSR series). The selected reference materials cover major rock types from ultramafic to felsic compositions, ensuring lithological representativeness of the dataset. Results show that the δ7Li values of the GSR series range from −3.0‰ to 13.9‰, while those of the USGS series range from −0.1‰ to 7.0‰, demonstrating that the GSR series has advantages over the USGS series in both lithological coverage breadth and isotopic composition span. Comparison with published data confirms that the analytical reproducibility of most GSR reference materials is better than 0.5‰, indicating good homogeneity. This study demonstrates that the GSR series rock reference materials possess the reliability and applicability as benchmarks for inter-laboratory Li isotopic data comparison. They can serve as important supplements to the USGS series, providing stable and accessible domestic quality control options for geochemical laboratories, reducing import dependence, and supporting Li isotopic tracing of geological processes.

     

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