福建漳州龙海铁染高岭土磁选尾矿的矿物特征分析

Investigation on Mineralogical Properties of Magnetic Separation Tailings of the Fe-contaminated Kaolin from Longhai,Zhangzhou,Fujian Province

对福建龙海红褐色铁染高岭土磁选尾矿进行了提纯,分离出强磁性含铁矿物,并对其进行了X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、穆斯堡尔谱和磁性测试等分析.研究结果表明:该尾矿所含的强磁性含铁氧化物并非文献报道的磁铁矿(Fe3O4),而是磁赤铁矿(γ-Fe2O3).穆斯堡尔谱分析未检测出样品中存在二价铁,结合XRD及磁性分析,表明磁选尾矿的磁性主要由磁赤铁矿引起.磁赤铁矿在福建省境内尚属首次发现.综合考虑该矿区其他伴生矿物的矿物成分、形貌等特征,及其所处的亚热带温暖潮湿性气候环境,确定该矿区具备形成磁赤铁矿的客观地质条件.通过对矿区的高岭土矿物形貌的大量分析,观察到罕见的高岭土形貌——卷曲型双壁或多壁微米管.

Iron oxide minerals,as the major constituents of the tailings from Fe-contaminated kaolin ores （Longhai,Fujian province, in southern China） after magnetic separation, have been characterized by using X-ray powder diffraction （XRD）, scanning electron mi- croscopy （SEM）, MOssbauer spectroscopy and magnetic measurements. These analyses show that the magnetic separation tailings do not consist of magnetite （Fe3 04 ） which was commonly assumed to be, but mainly maghemite （）＇-Fe2 03 ） plus a small amount of hem- atite （a-Fe2 03 ）. The isomer shift values of the measured sample in Mossbauer spectroscopy are quite different from those of divalent iron. Maghemite, herein identified by both XRD and M6ssbauer spectroscopy,has scarcely been reported in previous studies of kaolin ores in China,and this is the first reported location in Fujian Province. Maghemite as well as its associated mineral species,colors and morphologies imply that Longhai kaolin was formed under a subtropical environment, which is consistent with the conditions of maghemite in red soils observed in other locations （southern China and Hawaii,USA）. In addition, a rare morphology of halloysite, double-or multi-wall mirco-tube,was observed by using SEM for the first time as well.