石墨化碳质物质拉曼光谱温度计原理与应用

Fundamentals and Applications of Raman Spectroscopy of Carbonaceous Material (RSCM) Thermometry

总结了石墨化碳质物质拉曼光谱温度计的原理、样品制备、测试流程、影响因素和地质应用。该温度计基于沉积岩变质过程中发生的不可逆的碳质物质石墨化,利用拉曼光谱量化石墨化的程度,进而限制峰期变质的温度。近年来的研究量化了温度计算模型;同时发现除温度外,石墨化碳质物质拉曼光谱的影响因素还包括:石墨结构与成分的非均匀性、抛光制靶时引起的结构损伤、测试激光的波长和能量、赤铁矿含量等。因此,石墨化碳质物质拉曼光谱温度计的应用需要注意如下事项:野外需采集新鲜样品,排除风化产物赤铁矿的影响;使用标准的样品制备与测试流程,避免抛光和激光烧蚀的影响;并通过多点测试(通常为25个以上)的方式,统计测试结果的平均值与误差,以提高温度计算结果的准度。该方法适用的温度范围为100~700℃,在变质-变形分析、沉积岩埋藏历史、断层泥与有机质成熟度等研究领域均有较为广泛的应用。

This contribution attempts to summarize the principles, sample preparation, analytical procedures,influencing factors,and geological applications of Raman Spectroscopy of Carbonaceous Material(RSCM)thermometry. Irreversible graphitization of carbonaceous material in sedimentary rocks occurs during the process of reaching peak metamorphic temperature and can be effectively quantified by Raman spectroscopy.However,in addition to temperature,other factors,such as structural and compositional heterogeneity of carbonaceous materials,structural damage caused by polishing,wavelength and energy of laser used for analyses,hematite content,etc.,also have significant influence on the Raman signals of carbonaceous materials.Therefore,fresh samples should be collected for analyses to eliminate the influence of hematite. Further,standard experimental procedure should be practiced to avoid the effects of polishing and laser parameter setups.Additionally,multiple(usually more than 25)analyses per sample should be carried out for deriving statistical average and uncertainty values so as to minimize the influence of sample heterogeneity. RSCM thermometry is applicable to a temperature range between 100~700 ℃,and has been widely used in many fields of geological studies, including metamorphism and deformation of orogens, sediment burial history, fault gouge characteristics and evolution,and maturation grade of carbonaceous materials,etc.