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X射线荧光光谱微区分析在铅锌矿石鉴定上的应用

Application of in-situ Micro-X-ray Fluorescence Spectrometry in the Identification of Lead-Zinc Ore

  • 摘要: 自然界很多矿物存在类质同象现象,它们在显微镜下特征相似难以区分,对于这类矿物的鉴定,需要借助X射线衍射分析、电子显微镜、电子探针分析和离子探针分析等手段,获取矿物的化学成分和结构,为矿物鉴别提供有用的信息。本文以铅锌矿石中比较典型且易于收集的方铅矿(Pb 86.60%、S 13.40%)和闪锌矿(Zn 67.10%、S 32.90%)为例,借助偏反光显微镜,初步鉴定矿石的矿物特征;再利用X射线荧光光谱仪微区分析功能,对铅锌矿石标本进行定性和定量鉴定,对矿石所表现的各种特征做矿物学解释。实验结果表明,铅锌矿石标本中存在S、Pb、Zn、Cd等异常元素,并对闪锌矿标本中Zn、S、Fe、Cd等异常元素进行分布分析,绘制组分的二维或三维分布图显示各元素分布的异常区域高度一致;在电荷耦合器的实时监控下,对铅锌矿石标本靶区进行定点定量测定,根据所测组分含量,并结合矿物化学成分理论值定名为方铅矿和闪锌矿。本方法测定闪锌矿标本各组分的相对标准偏差(RSD,n=11)均小于4%,测定结果与电子探针测定结果吻合。本方法只要将矿石制成光片,无需喷碳处理,即可对铅锌矿石中主次量元素进行原位微区定性和定量分析,测定速度快且不破坏矿石标本,解决了类质同象矿物(如方铅矿和硒铅矿、闪锌矿和含铁闪锌矿等)在光学显微镜下鉴定困难的问题,提高了铅锌矿石定名的准确性,为岩矿鉴定工作提供一种新的技术手段。

     

    Abstract: Since isomorphous properties are common in many natural minerals, it is difficult to distinguish these minerals due to their similar characteristics under a microscope. The chemical composition and structure of these kinds of minerals can be obtained by using X-ray Diffraction Analysis, Electron Microscope Analysis, Electron Microprobe Analysis and Ion Probe Analysis, which can provide useful information for mineral identification. Galena (Pb 86.60%, S 13.40%) and sphalerite (Zn 67.10%, S 32.90%) contained in lead-zinc ore are more typical and are readily available to use as examples. The characteristic of minerals were determined preliminarily under the optical microscopy, and then the lead-zinc ore were qualitatively determined by using the in-situ micro-analysis function of RIGAKU ZSX Primus X-ray Fluorescence Spectrometer, which was applied to explain various characteristic of minerals. The experimental results show that the anomaly elements (S, Pb, Zn and Cd) were distinguished in some lead-zinc ores. According to the distribution analysis of the anomaly elements (Zn, S, Fe and Cd) in some sphalerite, 2D or 3D distribution images were established and the anomaly areas of elements are highly consistent. Under the real-time monitoring by charge-coupled device, the target area at the ore sample was quantitatively analyzed to identify the ore with its theoretical chemical components. The relative standard deviation (RSD, n=11) of determination of sphalerite sample components was less than 4%, which is comparable to the values obtained by Electron Microprobe. A new in-situ micro-analysis method of determining major and minor elements in lead-zinc ore is presented and is proved to be a fast non-invasive analytical technique. On the basis of the above analysis, a novel reasonable qualitative or quantitative analytical method for the identification of lead-zinc ore has been established, which provides a new method for the identification rock and minerals.

     

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