扫描电镜/能谱仪用于变质岩中榍石的鉴定

Application of scanning electron microscope/energy dispersive spectrometer in the identification of sphene in metamorphic rock

因榍石在变质岩中含量太少，晶体光学特征不明显，利用偏光显微镜及X射线衍射（XRD）等鉴定技术不易确定。实验利用扫描电镜／能谱仪检测矿物所含元素的种类，确定各元素的大致含量，根据定性分析结果，调用相应的标准样品数据文件，建立所测样品的文件清单。运用Casino程序和Quanta程序，据所测元素的强度值计算出样品中各元素的质量分数，依据矿物化学式中阴阳离子电价平衡的配比规律，计算出所测样品的化学组成。分析结果表明，所测8个样品中Si02质量分数在33．36％～34．1O％之间，CaO质量分数在25．85％～27．OO％之间，（Ti02＋Fe203＋A1203＋Cr02）质量分数在39．31％～4O．45％之间，与榍石主要化学成分基本一致。实验表明，同一件榍石样品平行测定1O次，O、Si、Ca、Ti、Fe元素测定结果的相对标准偏差（RSD）依次为O．23％、O．3O％、O．28％、O．26％、1．6％，精密度符合要求；经验证，实验方法的测定结果与电子探针波谱法测定结果相符。

Since the content of sphene in metamorphic rocks was very low and the optical characteristics of crystal were not obvious,it was difficultly identified by polarizing microscope and X-ray diffraction(XRD).The elements in ore were detected by scanning electron microscope/energy disperse spectrometer(SEM/EDS)to obtained the approximate content of elements.Based on the qualitative analysis results,the file list of testing samples was established using the corresponding data file of standard sample.The mass fraction of elements in sample was calculated according to the strength of elements using Casino procedure and Quanta procedure.Then,the chemical composition of testing sample was calculated according to the ratio law of anion-cation electrovalence balance in mineral chemical formula.The analysis results indicated that the mass fraction of SiO_2,CaO and(TiO_2+Fe_2O_3 +Al_2O_3 +CrO_2)in eight samples was33.36%-34.10%,25.85%-27.00% and 39.31%-40.45%,respectively,which was basically consistent with the main chemical composition of sphene.The experimental results indicated that the relative standard deviation(RSD,n=10)of O,Si,Ca,Ti and Fe in one sphene sample was 0.23%,0.30%,0.28%,0.26% and 1.6%,respectively.The precision could meet the requirements.The determination results of proposed method were consistent with those obtained by electron microprobe spectroscopy.