X射线粉晶衍射法在片麻岩鉴定与分类中的应用

利用偏光显微镜岩石薄片鉴定和X射线粉晶衍射物相分析技术，对34件片麻岩样品矿物组分进行检测.两种方法分析结果比对显示，有18件岩石样品定名一致，其余16件岩石样品详细定名有差异.偏光显微镜鉴定技术的优势在于能准确定出岩石构造和结构，能鉴定出更多的金属矿物、电气石、榍石、磷灰石、绿帘石，有效区分白云母和黑云母；X射线粉晶衍射法优势在于更准确区分出岩石中层状硅酸盐矿物绿泥石、蒙脱石和云母，确定钾长石、钠长石和石英矿物种类与含量.研究表明：片麻岩鉴定应该把偏光显微镜岩石薄片法与X射线粉晶衍射矿物半定量技术结合起来，才能更好地确定片麻岩的矿物组分，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 THE IDENTIFICATION AND CLASSIFICATION OF GNEISS

The mineral compositions of 34 gneiss samples are tested through thin section identification of polarizing microscope and X-ray powder diffraction phase analysis. Comparison shows that 18 of the 34 rock samples were named consistently by the two methods, while the other 16 were differently. The advantage of polarizing microscope identification is that it can accurately determine the structure and texture of rocks, identify most of metallic minerals and tourmaline, sphene, apatite and epidote as well, and effectively distinguish muscovite from biotite. The X-ray powder diffraction can exactly distinguish stratiform silicate minerals such as chlorite, montmorillonite and mica, and determine the mineral types and contents of potassium feldspar, albite and quartz. The results suggest that gneiss identification should combine the two methods to better determine mineral compositions and provide more objective data and analysis conclusions for geological study.