Improvement of the determination of element concentrations in quartz-hosted fluid inclusions by LA-ICP-MS and Pitzer thermodynamic modeling of ice melting temperature
Improvement of the determination of element concentrations in quartz-hosted fluid inclusions by LA-ICP-MS and Pitzer thermodynamic modeling of ice melting temperature
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DOI：
10.1016/j.gca.2012.04.040
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发表时间：
2012-08
影响因子：
5
通讯作者：
M. Leisen;J. Dubessy;M. Boiron;P. Lach
中科院分区：
文献类型：
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作者：
M. Leisen;J. Dubessy;M. Boiron;P. Lach
激光消融电感耦合等离子体质谱（LA-ICP-MS）已成为通过分析单个流体包裹体进行古流体化学研究的重要分析工具。流体包裹体中常量和微量元素含量的计算通常是基于经验公式，其意义和准确性值得怀疑。此外，缺乏用于估计单个流体包裹体中元素浓度的分析不确定性的方法。本文介绍了一种基于Pitzer热力学模型计算中低盐度流体包裹体中主要元素（Na、K、Mg和Ca）含量的方法。一个信号处理协议，结合新的方法也被开发来计算的浓度，为每个夹杂物，和每个主要和微量元素的不确定性。为了验证所提出的方法，合成和天然流体包裹体（从阿尔卑斯山石英脉）烧蚀与193 nm ArF准分子激光和分析与四极ICP-MS，配备了八极碰撞反应池。计算的和实际的元素浓度之间的差异（即准确度）不超过20%，并且在标准品（玻璃、毛细管中的溶液和合成流体包裹体）中，所有元素浓度的计算相对标准偏差（即精度）为± 10%。用这种新方法获得的阿尔卑斯山流体包裹体的元素浓度与以前使用激光诱导击穿光谱（LIBS）或破碎浸出方法测量的结果吻合得很好。最后，单个流体包裹体中每种元素的计算浓度和相关不确定度表明，LA-ICP-MS分析的灵敏度足够高，可以反映阿尔卑斯山古流体中主要和微量元素浓度的微小变化，最初认为具有恒定的化学性质。本文提出的新方法突出了古流体化学中的小但重要的变化，这些变化以前没有用传统的LA-ICP-MS数据处理检测到。
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has become an essential analytical tool for the study of paleofluid chemistry through the analysis of individual fluid inclusions. The calculation of major and trace element concentrations in fluid inclusions is usually based on empirical equations whose significance and accuracy are questionable. In addition, methods for estimation of analytical uncertainties element concentration in individual fluid inclusions are lacking. This study describes a method based upon Pitzer’s thermodynamic model for the calculation of major element (Na, K, Mg and Ca) concentrations in low-to moderate-salinity fluid inclusions. A signal processing protocol, used in combination with the new method is also developed to calculate the concentration, for each inclusion, and uncertainty for each major and trace element. In order to validate the proposed method, synthetic and natural fluid inclusions (from Alpine quartz veins) were ablated with a 193nm ArF excimer laser and analyzed with a quadrupole ICP-MS, equipped with an octopole collision–reaction cell. The difference between the calculated and actual element concentration (i.e. accuracy) does not exceed 20% and the calculated relative standard deviation (i.e. precision) for all element concentrations is ∼10% in standards (glasses, solutions in capillary tubes and synthetic fluid inclusions). The element concentrations obtained with this new method for the Alpine fluid inclusions are in good agreement with those previously measured using Laser Induced Breakdown Spectroscopy (LIBS) or crush-leach methods. Finally, the calculated concentrations and associated uncertainties determined for each element in individual fluid inclusions show that the sensitivity of LA-ICP-MS analysis is high enough to reflect small variations of major and trace element concentrations in the Alpine paleofluid, initially considered to have a constant chemistry. The new approach presented in this paper highlights small but significant variations in the paleofluid chemistry that were not previously detected with conventional LA-ICP-MS data processing.