X射线粉晶衍射法在变粒岩鉴定与分类中的应用

变粒岩的鉴定通常以显微镜鉴定技术为主,但在显微镜下区分颗粒细小的长石、石英及绿泥石、蒙脱石、云母等层状硅酸盐矿物十分困难,仅通过显微鉴定技术对变粒岩进行定名可能产生较大误差,这对地质填图和原岩恢复工作会造成一些偏差,导致得出错误的地质结论。随着X射线衍射分析技术的发展,该技术已广泛应用于矿物学和岩石学的研究,本研究将结合X射线粉晶衍射技术,对显微镜下难以区分的细小矿物进行鉴定。共选用23件变粒岩样品,利用X射线粉晶衍射分析和显微镜岩石薄片鉴定技术,对变粒岩矿物组分进行检测,用X射线粉晶衍射矿物半定量分析结果验证岩石薄片鉴定结果准确性。显微镜岩石薄片鉴定结果与X射线粉晶衍射物相分析结果对比显示,10件样品定名一致,其余13件样品详细定名有差异。通过分析产生差异的原因,可以认为显微镜岩石薄片鉴定优势在于能确定岩石结构和构造,以及常见矿物组分;X射线粉晶衍射法的优势在于能检测出显微镜下较难区分的细小石英和长石颗粒的相对含量,并能检测出颗粒较小的绿泥石、蒙脱石及云母等层状硅酸盐矿物,该方法对含量较少、颗粒较细的矿物检测效果较好。实验证明将显微岩石薄片鉴定技术和X射线粉晶衍射技术相结合,才能更准确对变粒岩进行定名,为地学研究提供更符合客观实际的技术数据和分析结论。

Application of X-ray Powder Diffraction Method in Identification and Classification of Leptite

BACKGROUND: The identification of leptite is usually based on microscopic identification technology, but it is very difficult to distinguish tiny feldspar, quartz, and layered silicate minerals such as chlorite, montmorillonite and mica using a microscope. There could be a large error in the naming of leptite by microscopic identification methods, which will cause errors in geological mapping and original rock recovery, leading to incorrect geological conclusions. The development of X-ray powder diffraction analysis technology has led to its wide use in the study of mineralogy and petrology.
OBJECTIVES: To identify tiny minerals that are difficult to distinguish under the microscope by using X-ray powder diffraction technology.
METHODS: A total of 23 leptite samples were selected. The mineral composition of leptite was detected by X-ray powder diffraction analysis and microscopic rock thin section identification technology. Semi-quantitative X-ray powder diffraction was used to verify the accuracy of the rock slice identification results.
RESULTS: The comparison between the identification results of the microscopic rock slices and the X-ray powder diffraction phase analysis results showed that 10 out of 23 samples had the same name. Analyzing the reasons for the difference, it can be found that the advantage of microscopic rock identification was that it can be used to determine rock texture and structure, as well as common mineral components. The advantage of the X-ray powder diffraction method was that it can be used to detect the relative content of tiny quartz and feldspar particles that were difficult to distinguish under the microscope, and can detect tiny layered silicate minerals such as chlorite, montmorillonite and mica, which was effective for detecting minerals with less content and finer particles.
CONCLUSIONS: Only by combining the microscopic rock thin identification technology and the X-ray powder diffraction technology can the leptite be named and classified more accurately. The combination of two techniques provides more objective technical data and analytical conclusions for geoscience research.