Experimental variable effects on laser heating of inclusions during Raman spectroscopic analysis
Experimental variable effects on laser heating of inclusions during Raman spectroscopic analysis
复制标题
DOI：
10.1016/j.chemgeo.2020.119928
复制
发表时间：
2021-01
期刊：
影响因子：
3.9
通讯作者：
Yuuki Hagiwara;Kenta Yoshida;A. Yoneda;J. Torimoto;J. Yamamoto
中科院分区：
文献类型：
--
作者：
Yuuki Hagiwara;Kenta Yoshida;A. Yoneda;J. Torimoto;J. Yamamoto
流体、熔体和矿物包裹体的拉曼光谱提供了对捕获时寄主矿物周围环境的物理化学条件的直接洞察。然而，由于激光激发包裹体的局部温度增强，所获得的拉曼光谱特征（如峰位）会发生改变，如果不加以校正，可能会产生系统误差，从而导致结论不正确。尽管激光加热的潜在影响不可忽略，但夹杂物的激光加热系数（B）（°C/mW）仍然没有解决。在这项研究中，我们发现从实验和热输运模拟来评估各种参数，如实验条件，矿物性质，夹杂物的几何形状affectBof夹杂物。为了评估影响激光加热的参数，我们测量了总共19个富CO2流体包裹体中的橄榄石，斜方辉石，单斜辉石，尖晶石和石英。结果表明，尖晶石中流体包裹体的B值最高（约为1000）。6 °C/mW），石英的温度最低（约为100 ℃/mW）。1 × 10−2°C/mW），与先前的推论一致。模拟结果表明，基质矿物的吸收系数与B值呈线性相关。当基质矿物的吸收系数（αh）大于包裹体的吸收系数（αinc）时，它是影响最大的参数。此外，虽然包裹体的尺寸和深度对B_（if αh>αinc）的影响很小，但寄主矿物的厚度和半径对B_（if αh> α inc）的影响很小。这些结果表明，在给定样品中待分析的夹杂物尺寸和深度的选择不会因为激光加热而导致拉曼数据中的任何系统误差，但是在样品制备时可以在一定程度上调整的主体半径和厚度会导致样品之间的系统误差。在分析过程中，包裹体温度升高至数十或数百度，特别取决于宿主矿物的几何形状和光学性质。因此，对包裹体的拉曼光谱分析进行热效应校正是获得可靠数据的必要条件。本文介绍了激光加热效应不可忽略的几种修正方法。
Raman spectroscopy for fluid, melt, and mineral inclusions provides direct insight into the physicochemical conditions of the environment surrounding the host mineral at the time of trapping. However, the obtained Raman spectral characteristics such as peak position are modified because of local temperature enhancement of the inclusions by the excitation laser, which might engender systematic errors and incorrect conclusions if the effect is not corrected. Despite the potentially non-negligible effects of laser heating, the laser heating coefficient (B) (°C/mW) of inclusions has remained unsolved. For this study, we foundBfrom experiments and heat transport simulation to evaluate how various parameters such as experimental conditions, mineral properties, and inclusion geometry affectBof inclusions. To assess the parameters influencing laser heating, we measuredBof a total of 19 CO2-rich fluid inclusions hosted in olivine, orthopyroxene, clinopyroxene, spinel, and quartz. Our results revealed that the measuredBof fluid inclusions in spinel is highest (approx. 6 °C/mW) and that of quartz is lowest (approx. 1 × 10−2°C/mW), consistent with earlier inferences. Our simulation results show that the absorption coefficient of the host mineral is correlated linearly withB. It is the most influential parameter when the absorption coefficient of the host mineral (αh) is larger than that of an inclusion (αinc). Furthermore, although our results indicate that both the inclusion size and depth have little effect onBifαh>αinc, the thickness and radius of the host mineral slightly influenceB. These results suggest that the choice of inclusion size and depth to be analyzed in a given sample do not cause any systematic error in the Raman data because of laser heating, but the host radius and thickness, which can be adjusted to some degree at the time of sample preparation, can cause systematic errors between samples.Our results demonstrate that, even with laser power of 10 mW, which is typical for inclusion analysis, the inclusion temperature rises to tens or hundreds of degrees during the analysis, depending especially on the host mineral geometry and optical properties. Therefore, correction of the heating effects will be necessary to obtain reliable data from Raman spectroscopic analysis of inclusions. This paper presents some correction methods for non-negligible effects of laser heating.