山东蒙阴金伯利岩中铬铁矿电子探针波谱分析

铬铁矿是金伯利岩型金刚石矿床中主要的指示性矿物之一.准确分析出铬铁矿化学组分中FeO、MgO、Cr₂O₃、Al₂O₃、TiO₂含量，不但对铬铁矿定名起决定性作用，对金伯利岩型金刚石矿床找矿也具有重要的指示意义.利用电子探针波谱技术对铬铁矿主量化学元素分析，通过所测样品微区化学成分含量推测矿物名称.25件单矿物样品微区化学成分分析结果统计显示：单矿物中主要化学成分FeO为15.666%~29.971%，MgO为7.286%~11.477%，Cr₂O₃为56.421%~71.111%；次要化学成分MnO为0.012%~0.382%，Al₂O₃为0.871%~8.993%，TiO₂为0.074%~3.375%.矿物化学成分总量为99.117%~100.877%，单矿物化学成分与铬铁矿化学组分相当.根据矿物人工重砂鉴定特征及A、B离子占位情况，可以确定所测样品为镁铬铁矿.

ELECTRON PROBE SPECTRUM ANALYSIS OF CHROMITE IN MENGYIN KIMBERLITES,SHANDONG PROVINCE

Chromite is one of the main indicator minerals in kimberlite diamond deposit.Accurate content analysis of the chemical compositions such as FeO,MgO,Cr₂O₃,Al₂O₃ and TiO₂ in chromite is the key for the naming of chromite,and significant indication for kimberlite diamond deposit prospecting as well.The electron probe spectroscopy is used to analyze the major chemical elements in chromite,and the micro-area chemical analysis of measured samples to infer the mineral name.The analysis results of 25 single mineral samples show that the contents of major chemical components are 15.666%-29.971%of FeO,7.286%-11.477%of MgO and 56.421%-71.111%of Cr₂O₃,with minor chemical components MnO 0.012%-0.382%,Al₂O₃0.871%-8.993%and TiO₂0.074%-3.375%.The total mineral chemical composition is 99.117%-100.877%.The chemical composition of single mineral is equivalent to that of chromite.According to the mineral characteristics by artificial heavy mineral identification and positions of ion groups A and B,it can be determined that the measured sample is magnochromite.