Effect of iron and nanolites on Raman spectra of volcanic glasses: A reassessment of existing strategies to estimate the water content
Effect of iron and nanolites on Raman spectra of volcanic glasses: A reassessment of existing strategies to estimate the water content
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DOI：
10.1016/j.chemgeo.2017.10.035
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发表时间：
2017-12-25
期刊：
影响因子：
3.9
通讯作者：
Spina, Laura
中科院分区：
文献类型：
--
作者：
Di Genova, Danilo;Sicola, Stefania;Spina, Laura
研究了含水地质玻璃中铁含量和铁纳米粒子对拉曼光谱的影响。测试了使用拉曼光谱估计水含量的当前程序，以探索铁含量、其氧化态和纳米粒子对模型可靠性的潜在影响。一个化学区间跨越从玄武岩到流纹岩，包括碱和富铁的组合物，水含量高达5.6%（重量），使用两个光谱仪进行了研究。当考虑无纳米石的样品时，在3550 cm（-1）处的带的面积与样品水含量线性相关，而不管化学成分如何。使用这种方法，以-0.15重量%的均方根误差（RMSE）再现数据。根据样品化学性质、水含量和采集条件，激光诱导的样品氧化导致在长采集时间（26分钟）下低估高达约90%的水含量。将水带区域归一化到硅酸盐带区域使这种限制最小化。这些条带之间的面积比与含水量线性相关，并且使用不同的基线程序并不能消除铁含量及其氧化态对这种相关性的依赖性。使用该程序，以~ 0.16重量%的RMSE再现数据。对于这两种方法，铁纳米粒子的存在可能导致低估水含量。
The effect of iron content and iron nanolites on Raman spectra of hydrous geologically-relevant glasses is presented. Current procedures to estimate the water content using Raman spectra were tested to explore potential effects of iron content, its oxidation state, and nanolites on models' reliability. A chemical interval spanning from basalt to rhyolite, including alkali-and iron-rich compositions, with water content up to 5.6 wt% was investigated using two spectrometers. When considering nanolite-free samples, the area of the band at 3550 cm(-1) linearly correlates with the sample water content regardless of chemical composition. Using this approach, data were reproduced with a root-mean-square error (RMSE) of -0.15 wt%. Depending on the sample chemistry, water content, and acquisition conditions the laser-induced sample oxidation led to underestimating the water content up to -90% with a long acquisition time (26 min). Normalising the water band region to the silicate band region minimises such a limitation. The area ratio between these bands linearly correlates with the water content and the use of different baseline procedures does not remove the dependence of such a correlation by the iron content and its oxidation state. With this procedure, data were reproduced with a RMSE of - 0.16 wt%. For both approaches, the presence of iron nanolites may result in underestimating the water content.