Application of X-ray Diffraction, X-ray Fluorescence Spectrometry and Electron Microprobe in the Identification of Basalt

Basalt identification is usually performed by microscope, so the appraisal results are easily influenced by personal professional level and subjective factors. Influenced by slice orientation, there are differences between the optical characteristics. Moreover, tiny mineral is also limited by optical microscope magnification itself. It is difficult to accurately identify basalt. Basalt rock mineral identification has been developed from traditional microscope identification to a variety of instrument determination, such as X-ray Diffraction (XRD), Electron Probe and X-ray Fluorescence Spectrometer (XRF), etc. XRD and the method of observation under microscope lens were used to identify two kinds of basalt, nvshan basalt (without alteration) and tuanshan basalt (with alteration). XRF and Electron Probe are used to validate the results of the appraisal. The Microscope identification analysis results show that the nvshan basalt (without alteration) is mainly composed of 74% matrix (inclusive of 44% plagioclase and 30% pyroxene) and 13% phenocryst, and also contains a small amount of 8% metal minerals and larger particles quartz crystal capture (5%). Microscopic identification of the matrix of plagioclase, by XRD can be further identified as labradorite, pyroxene mainly for ordinary pyroxene (monoclinic pyroxene), a small amount of metal minerals can be determined as ilmenite. Tuanshan basalt (after alteration) microscope identification is mainly composed of 75% matrix (inclusive of 50% plagioclase and 25% pyroxene) and 9% phenocryst, and also contains a small amount of chlorite filling the amygdale. Among them, the microscopic identification matrix of plagioclase can be further identified as microcline by XRD analysis, the alteration minerals montmorillonite instead of thin section identification of chlorite. The comprehensive appraisal result of XRD and related technologies show that nvshan basalt can be composed of minerals such as feldspar, pyroxene, ilmenite and the main minerals of Tuanshan basalt can be designated as microcline, pyroxene and montmorillonite. Research shows that single microscopic identification technology in the alteration mineral basalt will produce a large deviation. The introduction of the XRD technique can identify mineral species quickly and accurately, especially for smaller mineral particles.