Age determinations of rocks by in-situ Rb-Sr dating of minerals has the advantage of providing spatially resolved analysis without time-consuming preparation, but is hampered by isobaric and polyatomic interferences on Sr isotopes, especially ⁸⁷Rb. LA-ICP-MS/MS using N₂O as a reaction gas allows online chemical separation of ⁸⁷Rb from ⁸⁷Sr by measuring SrO⁺. Here, the method for in-situ Rb-Sr is optimized and applicability demonstrated for geological samples ranging from late Archean to 20 Ma in age.

Rb-Sr isotopes of multiple reference materials and geological samples have been analyzed by LA-ICP-MS/MS to evaluate the method for dating rocks throughout the geological record. The quality of Sr isotopic data can be greatly improved by external calibration of mass bias. For internal calibration, better accuracy is obtained with the addition of H₂ as a trace molecular gas. The elemental fractionation of Rb and Sr during LA-ICP-MS/MS analysis varies for different reference materials. We find that the matrix of NIST SRM 610 renders it unsuitable for correction of ⁸⁷Rb/⁸⁶Sr. The Mica-Mg reference material is preferred for calibration of ⁸⁷Rb/⁸⁶Sr of micas despite showing significant Rb-Sr fractionation.

In-situ Rb-Sr ages were determined for igneous samples ranging in age from 20 Ma to Mesoproterozoic, confirming accurate application of the method to samples of widely differing ages. The most accurate isochron ages were obtained with ⁸⁷Rb/⁸⁶Sr calibrated against Mica-Mg. Application to two metamorphic gneisses with late Archean protoliths from Labrador and Finland reveal thermal events at 1.66–1.70 Ga when they were part of a large Paleoproterozic active margin along the southern edge of Laurentia-Baltica. Data collected for minerals with differing closure temperatures for the Rb-Sr system allow detection of thermal events not recorded by other geochronological systems, indicating a huge potential of this technique not only for accurately dating samples, but also for providing previously inaccessible information on metamorphic histories.

通过矿物的原位Rb-Sr 测年确定岩石的年龄具有无需耗时准备即可提供空间分辨分析的优势，但受到 Sr 同位素，尤其是⁸⁷ Rb 的同量元素和多原子干扰的阻碍。LA-ICP-MS/MS 使用 N ₂ O 作为反应气体，通过测量 SrO ⁺可以在线化学分离⁸⁷ Rb 和^{87 Sr。}在这里，对原位Rb-Sr 的方法进行了优化，并证明了其适用于年龄从太古代晚期到 20 Ma 的地质样品。

已通过 LA-ICP-MS/MS 分析了多种参考材料和地质样品的 Rb-Sr 同位素，以评估整个地质记录中岩石的年代测定方法。通过质量偏差的外部校准可以大大提高 Sr 同位素数据的质量。对于内部校准，添加 H ₂作为痕量分子气体可获得更好的准确度。LA-ICP-MS/MS 分析过程中 Rb 和 Sr 的元素分馏因不同的参考物质而异。我们发现 NIST SRM 610 的基质使其不适合校正⁸⁷ Rb/ ⁸⁶ Sr。尽管显示出明显的 Rb-Sr 分馏，但云母-Mg 参考材料更适合校准云母的⁸⁷ Rb/ ^{86 Sr。}

对年龄从 20 Ma 到中元古代的火成岩样品进行了原位Rb-Sr 年龄测定，证实了该方法对年龄差异很大的样品的准确应用。^使用87 Rb/ ⁸⁶获得最准确的等时线年龄Sr 用 Mica-Mg 校准。对来自拉布拉多和芬兰的两个具有晚期太古代原岩的变质片麻岩的应用揭示了 1.66-1.70 Ga 的热事件，当时它们是劳伦蒂亚-波罗的海南部边缘大型古元古代活动边缘的一部分。为 Rb-Sr 系统收集的具有不同闭合温度的矿物的数据允许检测其他地质年代学系统未记录的热事件，这表明该技术不仅可以用于准确定年样品，而且还可以提供以前无法获得的关于变质历史的信息.