Quantification of water content in silicate glasses is of vital significance in understanding magma evolution and metamorphic anataxis. Here we provide a method for the determination of total dissolved water content and water speciation in silicate melts by confocal laser Raman spectrometry based on a set of hydrous rhyolitic glasses. A series of alumino-silicate glasses with water contents from 0.33 to 9.05% m/m were synthesised in a piston cylinder apparatus. Synchrotron-FTIR mapping shows that these glasses have relatively homogeneous distributions of dissolved water. Total water contents of the glasses were precisely measured by TC/EA-MS and FTIR. Both external and internal calibration were established for the quantitative analysis of water content and water speciation in the silicate glasses based on excellent linear correlation between total dissolved water content and integrated area of the water Raman band. Furthermore, by decomposing the total water Raman bands into four Gaussians components, the relative concentration of water speciation (OH groups and molecules H₂O_m) dissolved in the glasses was determined with a similar trend to water speciation data derived from FTIR. We suggest that the relative concentration of water speciation can be estimated in rhyolitic glasses with 4–8% m/m H₂O. Our work provides an accurate method to determine total water content and a potential tool to limit the relative concentration of water speciation dissolved in silicic glasses.

中文翻译：

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合成流纹岩玻璃中水含量和形态的定量：优化共焦拉曼光谱分析方法

硅酸盐玻璃中水含量的定量对于理解岩浆演化和变质锐化具有重要意义。在这里，我们提供了一种基于一组水合流纹岩玻璃的共焦激光拉曼光谱测定硅酸盐熔体中总溶解水含量和水形态的方法。一系列含水量为 0.33 至 9.05% m/m的铝硅酸盐玻璃 在活塞缸装置中合成。同步加速器-傅立叶变换红外图谱显示这些玻璃具有相对均匀的溶解水分布。通过 TC/EA-MS 和 FTIR 精确测量玻璃的总水含量。基于总溶解水含量和水拉曼谱带积分面积之间良好的线性相关性，建立了外部和内部校准，用于硅酸盐玻璃中水含量和水形态的定量分析。此外，通过将总水拉曼带分解为四个高斯分量，水形态的相对浓度（OH基团和分子H ₂ O _m）溶解在玻璃中的测定与 FTIR 得出的水形态数据具有相似的趋势。我们建议可以用 4-8% m/m H ₂ O 来估计流纹岩玻璃中水形态的相对浓度。我们的工作提供了一种确定总水含量的准确方法和限制水形态相对浓度的潜在工具溶于硅玻璃。