河南卢氏官坡伟晶岩中锂辉石的矿物学特征研究

A mineralogical study of spodumene from Guanpo pegmatites in Lushi,Henan Province

对河南卢氏官坡伟晶岩中的锂辉石进行了系统的矿物学特征研究。通过手标本和薄片观察得出含锂辉石伟晶岩的主要矿物组成为锂辉石、石英、长石和白云母。其中锂辉石矿物结晶程度好,颗粒粗大,易于分离。运用X射线粉晶衍射分析、红外光谱分析、X射线荧光光谱分析以及微量元素分析可知,锂辉石中氧化锂的含量为6.56%～6.82%,具有重要的开发价值。锂辉石的稀土元素配分中存在一定程度铕负异常,说明锂辉石是在结晶分异过程中斜长石结晶析出后而逐渐结晶析出的。

There are abundant rare metals such as Li,Nb,Ta,Rb,Cs and Be in granitic pegmatites of Lushi County,Henan Province.The paragenetic minerals include spodumene,lepidolite,elbaite,quartz,feldspar,muscovite etc.The proved reserves of spodumene are highest in these minerals.The authors made a systematic study of mineralogical characteristics of spodumene from Guanpo pegmatites in Henan Province by such means as hand specimen and microscopic observation,X-ray powder diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,X-ray fluorescence analysis and ICP-MS.According to hand specimen and microscopic observation,the main mineral compositions of spodumene-bearing granitic pegmatites are spodumene,quartz,feldspar and muscovite.The average content of spodumene is about 40% in the pegmatite ore.Spodumene commonly occurs as coarse pillar and flaky crystals.There are relatively fine-grained garnet,tantalite and pyrite in pegmatitese.X-ray powder diffraction and infrared spectroscopic analyses show that spodumene is in a good crystallization condition with less impurities.Infrared spectroscopic data of samples show some deviations in comparison from standard data of spodumene.These deviations mainly suggest that Li—O vibration shifts to high wave（466 cm-1,472 cm-1）,and AlⅥ—O bending vibration（588 cm-1,585 cm-1）and AlⅥ—O elastic vibration（637 cm-1,639 cm-1）shift to low wave.The reason of producing deviation lies in isomorphous substitution in crystal lattice of spodumene with substituting Na＋,K＋,Ca2＋ for Li＋ or substituting Mg2＋,Fe2＋,Mn2＋ for Al3＋.Lithium content is high in the spodumene,as shown by the analysis of trace elements.The content of Li2O in spodumene is 6.56%～6.82%.X-ray fluorescence analyses show that there are isomorphous substitution in crystal lattice of spodumene,with substituting Na＋,K＋,Ca2＋ for Li＋.There are negative abnormal phenomena of europium（Eu）in the spodumene,as shown by analyzing chondrite-normalized REE patterns of spodumene from Guanpo.Regional geological geomorphology of this area shows that spodumene was crystallized later than plagioclase in the course of magmatic differentiation.The production of Eu anomaly is related to plagioclase crystallization in magmatites.Different minerals have different REE distribution coefficients.Plagioclase has much stronger distribution coefficient to Eu than to other REE.Eu anomaly was formed in the course of magmatic differentiation with plagioclase crystallization.Spodumene crystallization occurred later than plagioclase crystallization.The research results show the content of Li2O in spodumene has reached industrial grade.Spodumene is an important ore material for lithium exploration in this area.