Magnesium isotopic analysis of olivine by laser-ablation multi-collector ICP-MS: composition dependent matrix effects and a comparison of the Earth and Moon
Magnesium isotopic analysis of olivine by laser-ablation multi-collector ICP-MS: composition dependent matrix effects and a comparison of the Earth and Moon
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DOI：
10.1039/b510719a
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发表时间：
2006-12
影响因子：
3.4
通讯作者：
M. Norman;M. McCulloch;H. O’Neill;G. Yaxley
中科院分区：
文献类型：
--
作者：
M. Norman;M. McCulloch;H. O’Neill;G. Yaxley
采用ArF 193 nm准分子激光器，用激光烧蚀多接收器ICP-MS测定了橄榄石的镁同位素组成。基于地幔橄榄石重复分析的分析精密度为0.2 permil（2SD）。这比通过离子微探针或热电离质谱法报道的好大约一个数量级，但比通过具有类似信号强度的溶液抽吸多收集器ICP-MS获得的精确度低大约2-3倍。合成橄榄石的分析表明，一个组合物依赖的基质效应，系统较重的同位素组成的橄榄石与较低的Mg#测量。这种基质效应的大小随激光操作参数如光斑直径和重复率而变化，并且似乎是由于在烧蚀部位而不是在等离子体内的质量依赖性同位素分馏。经基体效应校正后，月球橄榄石的Mg同位素组成与地球地幔一致。
Magnesium isotopic compositions of olivine were measured by laser-ablation multi-collector ICP-MS using an ArF 193 nm excimer laser. Analytical precision based on replicate analyses of mantle olivine is ∼0.2 permil (2SD). This is about an order of magnitude better than has been reported by ion microprobe or thermal ionization mass spectrometry, but about a factor of 2–3 less precise than can be obtained by solution aspiration multi-collector ICP-MS with a similar signal intensity. Analysis of synthetic olivines demonstrates a composition-dependent matrix effect in which systematically heavier isotopic compositions are measured in olivines with lower Mg#. The magnitude of this matrix effect varies with laser operating parameters such as spot diameter and repetition rate, and appears to be due to mass-dependent isotope fractionation at the ablation site rather than within the plasma. After correction for matrix effects, the Mg isotopic composition of olivine from the Moon is shown to be identical with that of the Earth’s mantle.