X射线荧光光谱分析技术在大理岩鉴定与分类中的应用

大理岩的鉴定与分类主要依靠岩石薄片鉴定及X射线衍射(XRD)矿物半定量检测技术。工作中发现,岩石薄片鉴定技术及XRD矿物半定量检测技术所测得矿物组分含量很少一致,这就需要引入其他技术对岩石薄片鉴定及XRD矿物半定量检测结果加以验证。本文利用X射线荧光光谱仪(XRF)对野外采集的32件大理岩样品进行全岩化学成分分析,以岩石化学成分为基础,分析岩石杂质系数、镁质系数和钙质系数特征,对大理岩进行分类。结果表明:方解石大理岩、白云石大理岩、菱镁矿大理岩的镁质系数值分别为0.01~0.13、0.40~0.46、0.97~0.98,钙质系数值分别为0.78~0.84、0.30~0.49和0.01~0.02,不同类型大理岩的钙质系数和镁质系数明显不同,可以作为划分大理岩类型的主要依据。当岩石中SiO_2+Al_2O_3含量大于35%(杂质系数大于为1.20),不能定为大理岩,只有岩石中SiO_2+Al_2O_3含量小于30%(杂质系数小于1.00)时,可定为大理岩。杂质系数、镁质系数和钙质系数的应用,能够校正岩石薄片鉴定法及XRD矿物半定量法矿物含量检测不一致的问题,使大理岩分类定名更加准确。

Application of X-ray Fluorescence Spectroscopy in Identification and Classification of Marble

The identification and classification of marble depended mainly on the identification of rock slices and the semi-quantitative detection of minerals by X-ray Diffraction (XRD). It was found that the results of identification of rock slices were not always consistent with those of the semi-quantitative detection by XRD. Therefore, it is necessary to introduce other techniques to verify the results of thin section observation and XRD semi-quantitative analysis. 32 marble samples were analyzed by X-ray Fluorescence Spectrometer, the results and finding of which are reported in this paper. Based on the chemical composition of rock, rock impurity, magnesite, and calcareous coefficients are used to classify the marble. The results show that magnesite coefficients of calcite marble, dolomite marble, and magnesite marble are 0.01-0.13, 0.40-0.46 and 0.97-0.98, respectively. Calcareous coefficients are 0.78-0.84, 0.30-0.49 and 0.01-0.02, respectively. Different types of marble have various magnesia and calcareous coefficients, which can be used as the main basis for the division of marble types. Only the contents of SiO₂+Al₂O₃ in rocks are less than 30% (impurity coefficient less than 1.00), then can be classified as marbles. The establishment and application of impurity, magnesia and calcareous coefficients in marble can be used to correct the inconsistent results between thin section observation and X-ray Powder Diffraction mineral semi-quantitative analysis, making marble classification more accurate.