A micro-reflectance IR spectroscopy method for analyzing volatile species in basaltic, andesitic, phonolitic, and rhyolitic glasses
A micro-reflectance IR spectroscopy method for analyzing volatile species in basaltic, andesitic, phonolitic, and rhyolitic glasses
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用于分析玄武岩、安山岩、声纹岩和流纹岩玻璃中挥发性物质的微反射红外光谱方法
DOI：
10.2138/am.2013.4277
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发表时间：
2013
影响因子：
3.1
通讯作者：
J. Larsen
中科院分区：
文献类型：
--
作者：
P. King;J. Larsen
摘要地质玻璃的挥发分含量可用来模拟岩浆房和脱气过程，因此，对玻璃中挥发分的小规模分析技术有着相当大的兴趣。红外（IR）光谱法具有确定玻璃中挥发物形态的优点（例如，OH-、分子H2O、分子CO2和CO 3 2-）。然而，最常用的红外方法，微透射红外光谱法，样品制备是复杂的，因为玻璃必须制备薄，平行面晶片。拉曼分析虽然对贫Fe样品有价值，但可能难以用于富Fe玻璃。我们已经校准了微反射红外方法，用于确定挥发性物质，使用计算的Kramers-Kronig吸光度（KK-Abs）。只需要玻璃的一面被抛光的光谱。该方法比其他难以确定红外波段基线的反射率方法更容易使用。总H2O重量% = m·（3600 cm-1 KK-吸光度），其中m是从数据拟合获得的校准线的斜率。m值与一系列铝硅酸盐玻璃组合物的计算折射率n相关，从而允许将该技术应用于具有未知校准斜率的样品。对于钙碱性安山岩玻璃，我们确定了分子H2O，分子CO2和CO 3 2-的微反射红外测量的校准斜率。该方法已被校准用于具有高达6.76wt%总H2O的玻璃（但可用于具有超过20wt%总H2O的玻璃），并且已被校准用于具有高达0.575wt%总CO2的玻璃。该技术提供了一种分析样品中挥发物丰度的方法，这些样品不可能用透射显微红外技术分析或准备分析。我们已经确定了易挥发的内容，如破裂，气泡，或含晶体的玻璃形成的火山或冲击过程或在高压气泡成核实验和H扩散实验中的脆弱的样品。我们监测了玄武岩玻璃风化过程中的吸氢量，这些玻璃不能抛光，并确定了熔融包裹体和浮石中的挥发物
Abstract Volatile contents of geologic glasses are used to model magma chamber and degassing processes, thus, there is considerable interest in small-scale analytical techniques for analyzing volatiles in glasses. Infrared (IR) spectroscopy has the advantage of determining volatile speciation in glasses (e.g., OH-, molecular H2O, molecular CO2, and CO3 2-). However, sample preparation for the most common IR method used, micro-transmission IR spectroscopy, is complicated because glasses must be prepared as thin, parallel-sided wafers. Raman analysis, while valuable for Fe-poor samples, can be difficult to use for Fe-rich glasses. We have calibrated a micro-reflectance infrared method for determining volatile species using calculated Kramers-Kronig absorbance (KK-Abs.) spectra that requires that only one side of a glass be polished. The method is easier to use than other reflectance methods where it is difficult to determine the baseline for the IR bands. Total H2O wt% = m·(3600 cm-1 KK-Abs.), where m, is the slope of the calibration line that is obtained from a fit to the data. The m value is related to the calculated refractive index, n, for a range of aluminosilicate glass compositions allowing the technique to be applied to samples with unknown calibration slopes. For calc-alkaline andesite glasses we determined calibration slopes for micro-reflectance IR measurements of molecular H2O, molecular CO2, and CO3 2-. The method has been calibrated for glasses with up to 6.76 wt% total H2O (but is useful for glasses with more than 20 wt% total H2O) and has been calibrated for glasses with up to 0.575 wt% total CO2. This technique provides a means to analyze volatile abundances in samples that are not possible to analyze or prepare for analysis with transmission micro-IR techniques. We have determined volatile contents in fragile samples such as cracked, vesicular, or crystal-bearing glasses formed by volcanic or impact processes or in high-pressure bubble nucleation experiments and H diffusion experiments. We have monitored H uptake during weathering of basaltic glasses that cannot be polished and determined volatiles in melt inclusions and pumice