The isotopic composition of lithium (Li) in clinopyroxene (Cpx), determined via in situ micro-analysis, has been employed as a potential geochemical tool for studying various geological processes such as crust-mantle recycling, silicate weathering and fluid-rock interaction. To obtain precise and accurate Li isotopic compositions in Cpx by LA-MC-ICP-MS, synthetic Cpx matrix-matched reference materials (RMs) were prepared in this study. Six Cpx-matrix RMs were prepared by mixing metallic oxides with GSP-2 (granodiorite) or pure L-SVEC solution and melting them into glasses (GSP-2 + oxide; L-SVEC + oxide). Two representative synthetic glasses, CPXA01 and CPXB01, were subjected to a series of analyses to investigate the possible qualification of the RMs for in situ Li isotope measurement by LA-MC-ICP-MS, including elemental homogeneity analysis (elemental mapping analysis and spot analysis), Li isotopic homogeneity analysis and accurate Li isotopic determination. The applicability of the synthetic Cpx-matrix RMs was highlighted by comparing the δ⁷Li values of three natural Cpx calibrated against the synthetic Cpx-matrix RMs and other commonly used RMs with different matrices (NIST SRM 612, BCR-2G, GOR128-G, StHs6/80-G, KL2-G and T1-G), respectively. Additionally, CPXB01-05 RMs with the same matrix but different Li contents were prepared to explore the Li content mismatch effect, which is significant for accurate determination of in situ Li isotopic composition by LA-MC-ICP-MS. The results of the cross-calibration of Li isotopes in CPXA01 and CPXB01 suggested no obvious Li isotopic fractionation between the two types of glasses (GSP-2 + oxide; L-SVEC + oxide). Thus, the two methods of producing Cpx-matrix RMs are suitable for preparing the matrix-matched RMs for in situ microanalysis for Li isotopes.

中文翻译：

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开发用于 LA-MC-ICP-MS 原位锂同位素测量的合成单斜辉石标准物质

通过原位微分析测定的单斜辉石 (Cpx) 中锂 (Li) 的同位素组成已被用作研究各种地质过程（例如壳幔循环、硅酸盐风化和流体-岩石相互作用）的潜在地球化学工具。为了通过 LA-MC-ICP-MS 获得精确且准确的 Cpx 中的 Li 同位素组成，本研究制备了合成的 Cpx 基质匹配参考材料 (RM)。通过将金属氧化物与 GSP-2（花岗闪长岩）或纯 L-SVEC 溶液混合并将其熔化成玻璃（GSP-2 + 氧化物；L-SVEC + 氧化物）来制备六种 Cpx 基质 RM。对两种代表性合成玻璃 CPXA01 和 CPXB01 进行了一系列分析，以研究 RM 的原位可能资格采用LA-MC-ICP-MS进行Li同位素测量，包括元素均匀性分析（元素图分析和点分析）、Li同位素均匀性分析和精确的Li同位素测定。通过比较三种天然 Cpx 的 δ ⁷ Li 值，并与合成 Cpx 基质 RM 和其他具有不同基质的常用 RM（NIST SRM 612、BCR-2G、GOR128-G）进行校准，强调了合成 Cpx 基质 RM 的适用性、StHs6/80-G、KL2-G 和 T1-G）。此外，制备了相同基质但不同锂含量的CPXB01-05 RM，探索锂含量错配效应，这对于原位准确测定具有重要意义。由 LA-MC-ICP-MS 测定的 Li 同位素组成。CPXA01 和 CPXB01 中 Li 同位素的交叉校准结果表明，两种类型的玻璃（GSP-2 + 氧化物；L-SVEC + 氧化物）之间没有明显的 Li 同位素分馏。因此，这两种生产 Cpx 基质 RM 的方法适合制备用于Li 同位素原位微量分析的基质匹配 RM。