High‐Precision Mass‐Dependent Molybdenum Isotope Variations in Magmatic Rocks Determined by Double‐Spike MC‐ICP‐MS
High‐Precision Mass‐Dependent Molybdenum Isotope Variations in Magmatic Rocks Determined by Double‐Spike MC‐ICP‐MS
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DOI：
10.1111/j.1751-908x.2015.00388.x
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发表时间：
2016-09
影响因子：
3.8
通讯作者：
M. Willbold;K. Hibbert;Y. Lai;H. Freymuth;R. Hin;C. Coath;Flurin Vils;T. Elliott
中科院分区：
文献类型：
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作者：
M. Willbold;K. Hibbert;Y. Lai;H. Freymuth;R. Hin;C. Coath;Flurin Vils;T. Elliott
在地质时间尺度上，海洋和岛弧岩石中钼同位素比率的小质量依赖变化可能是经蚀变的海洋地壳和沉积物在会聚板块边缘再循环进入地幔的结果。然而，钼同位素数据的精确测定和精确到足以识别这些微妙的同位素差异仍然具有挑战性。超过200毫克的大样本需要进行化学处理，以分离出足够的钼，以便使用双峰MC - ICP - MS技术进行足够高精度的同位素分析。现有的方法要么无法处理如此大量的硅酸盐材料，要么需要几个不同的化学处理步骤，使得分析非常耗时。在这里，我们提出了一种新的、高效的单通色谱交换技术，用于从硅酸盐和金属基体中化学分离钼。为了验证我们的新方法，我们分析了美国地质调查局的参考物质BHVO‐2和BIR‐1。我们的新数据与先前发表的这两种参考材料的更复杂和耗时的方法得出的结果一致。我们还为USGS标准材料AGV‐2、GSJ标准材料JB‐2以及金属NIST SRM 361提供了第一个钼同位素数据。
Small mass‐dependent variations of molybdenum isotope ratios in oceanic and island arc rocks are expected as a result of recycling altered oceanic crust and sediments into the mantle at convergent plate margins over geological timescales. However, the determination of molybdenum isotope data precise and accurate enough to identify these subtle isotopic differences remains challenging. Large sample sizes – in excess of 200 mg – need to be chemically processed to isolate enough molybdenum in order to allow sufficiently high‐precision isotope analyses using double‐spike MC‐ICP‐MS techniques. Established methods are either unable to process such large amounts of silicate material or require several distinct chemical processing steps, making the analyses very time‐consuming. Here, we present a new and efficient single‐pass chromatographic exchange technique for the chemical isolation of molybdenum from silicate and metal matrices. To test our new method, we analysed USGS reference materials BHVO‐2 and BIR‐1. Our new data are consistent with those derived from more involved and time‐consuming methods for these two reference materials previously published. We also provide the first molybdenum isotope data for USGS reference materials AGV‐2, the GSJ reference material JB‐2 as well as metal NIST SRM 361.