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红外光谱/扫描电镜等现代大型仪器岩石矿物鉴定技术及其应用

Application of IR/SEM and Other Modern Instruments for Mineral Identification

  • 摘要: 传统的光学显微镜由于分辨率、放大倍数的限制,对于细微颗粒的定性分析不准确,矿物的定量分析存在一定的误差,纳米-微米级矿物形貌及结构特征的观察束手无策。随着油气勘探及地质找矿的不断深入,需要提供岩石中所有矿物、孔隙及微量元素的信息,因此整合傅里叶红外光谱仪、X射线衍射仪、拉曼光谱仪、扫描电镜的优点,建立以大型仪器为基础的岩石矿物鉴定方法是当前地质工作的需要。红外光谱光谱范围为7500~370 cm-1,能对固、液、气样品中含量高于30%的矿物进行快速、准确的定性分析; 主要用于有机质分析,其次还可对部分具有极性键的无机化合物及金属氧化物进行分析。X射线衍射仪能快速地对样品中含量大于15%的矿物进行较为准确的定量分析;现今主要用于各类晶质矿物的定性分析,同时也可对碳酸盐岩矿物等不含水矿物进行定量分析。拉曼光谱仪光谱范围为200~1000 nm,空间分辨率为横向0.5 μm、纵向2 μm,通过对包裹体进行测试能直接获得成岩过程中的温度、压力、流体成分等信息;目前主要用于流体包裹体成分的测试,其次还可对分子极化度会发生变化的液态、粉末及固体样品进行定性分析。扫描电镜分辨率达到1 nm,能清晰地观察到纳米-微米级矿物的形貌特征及矿物的结构特征;主要用于纳米-微米级的任何非磁性固体矿物的形貌及相关关系的观察。通过大型仪器建立的岩石矿物鉴定方法具有更高的分辨率,显著地提高了岩矿鉴定的精准度,大大拓宽了岩矿鉴定的范围(如鉴定纳米/微米级的矿物、矿物的不同变种等),能够全面、精准地提供岩石矿物的矿物含量和矿物组成、客观准确的成岩作用信息、清晰的矿物微观形貌及结构特征,而且仪器功能相互重叠,测试结果相互验证,保证了测试结果的可靠性。与传统光学显微镜鉴定方法相比,现代大型仪器岩石矿物鉴定技术为揭示矿物间的共生、反应、演化、岩石的成因、沉积/成岩环境等提供了依据,为地质工作提供准确、全面的矿物定性定量、组构特征及成岩作用等信息,为地质工作的顺利完成奠定了坚实的基础。

     

    Abstract: Due to the limitations of resolution and magnification for the traditional optical microscope, qualitative analysis for fine particles is inaccurate and quantitative analysis of minerals contains errors, which makes it impossible to obtain accurate nano to micron grade mineral morphology and structure characteristics. With the development of oil and gas exploration and geological prospecting, all minerals in rocks and pores, and trace element information are required. Thus, integrating the Fourier Infrared Spectrometer, X-ray Diffractometer, Raman Spectrometer, and Scanning Electron Microscope, to obtain a mineral identification method on the basis of large-scale instruments, as described here, is essential for current geological work. The Fourier infrared spectral range is 7500-370 cm-1, and is ideally suited for rapid and accurate qualitative analysis of minerals of more than 30% content in solid, liquid, or gas samples. It is mainly used for organic matter analysis, and then for some inorganic compounds with polar bond and metal oxide. The minerals which have greater concentration than 15% in the sample can be accurately analyzed quantitatively by X-ray Diffractometer. Nowadays, it is mainly used for qualitative analysis of all kinds of crystal mineral, also for analysis of carbonate minerals that without hydrated. The Raman Spectrometer spectral range is 200-1000 nm and the horizontal and vertical spatial resolutions are 0.5 μm and 2 μm, which can be utilized to obtain the temperature, pressure and fluid composition in the process of diagenesis based on the inclusion study. At present, it is mainly used for fluid inclusion composition test, then for qualitative analysis of liquid, powder and solid samples that have polarizability molecular. The resolution of the scanning electron microscope is up to 1 nm, which is suitable to clearly observe the morphology of nano-micron grade mineral characteristics and structure characteristics. It is mainly used for any non magnetic nano-micron grade of solid mineral morphology observation and related relations. This method of rock mineral identification through large-scale instruments is a significant improvement over traditional methods by being able to identify different varieties of minerals at the micro and nano level. It can also provide comprehensive, precise rock mineral content and mineral composition, accurate diagenetic mineral microstructure and structure characteristics. The overlapping instrument functions and mutual verification can ensure the reliability of test results. Compared with the traditional optical microscope identification method, modern large-scale instruments reveal the information on mineral symbiosis, reaction, evolution, the formation of the rock, sedimentary/diagenetic environment, which provide accurate, comprehensive qualitative/quantity, fabric characteristics and diagenesis minerals information in order to complete geological work.

     

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