电子探针波谱法在辉石种属鉴定中的应用

APPLICATION OF ELECTRON PROBE SPECTRUM METHOD IN THE SPECIES IDENTIFICATION OF PYROXENE

变质岩中辉石显微镜下以高正突起、辉石式解理和干涉色为主要鉴定特征．辉石族矿物有斜方辉石和单斜辉石2个亚族，其中斜方辉石亚族有7种辉石类型，单斜辉石亚族有12种辉石类型．为了验证岩石薄片鉴定结果的准确性，往往是利用x射线粉晶衍射技术进行比对分析．岩石中有几种辉石及辉石类型，x射线粉晶衍射方法则无法区分，本次研究是利用电子探针波谱技术对矿物主量元素进行分析，通过所测样品微区化学成分含量推测矿物名称．25件样品微区化学成分分析结果统计显示：MgO为8．36％。17．34％，FeO为27．57％～39．77％，SiO2为47．94％～52．70％；次要成分含量：Cr2O3为0．01％～6．28％，Na2O为0．00％-0.19％，Al2O3为0．43％。3．11％，CaO为0．38％～1．94％，MnO2为0．09％～0．79％；总量为99．64％～100．00％．化学成分与紫苏辉石组分相当，可以确定所测样品为紫苏辉石．

The main identification marks of pyroxene in metamorphic rocks under microscope are high positive relief, pyroxene-type cleavage and interference color. The mineral family of pyroxene is consisted of two subfamilies： orthopyroxene and clinopyroxene. The orthopyroxene subfamily includes 7 species of pyroxene; while the clinopyroxene, 12 species. In order to verify the accuracy of rock thin section identification results, X-ray powder diffraction technique is usually used for comparative analysis. There are several kinds of pyroxene and pyroxene species in rocks, which cannot be distinguished by the X-ray powder diffraction method. This study adopts electronic probe spectrum technique to analyze the major elements of mineral and speculate the mineral name with microanalysis of chemical composition of samples. Statistics of microanalysis for 25 samples show the chemical composition of the mineral： 8.36%-17.34% of MgO, 27.57%-39.77% of FeO and 47.94% - 52.70% of SiO2, with minor Cr2O3 （0.01%-6.28%）, Na20 （0.00%-0.19%）, Al2O3 （0.43%-3.11% ）, CaO （0.38% ~1.94% ） and MnO2 （0.09%-0.79% ）. The chemical composition of tested samples corresponds to that of hypersthene, thus it can be determined as hypersthene.