自动矿物分析技术在鄂尔多斯盆地砂岩型铀矿矿物鉴定和赋存状态研究中的应用

鄂尔多斯盆地是我国重要的砂岩型铀矿成矿区之一。铀矿物赋存状态研究对砂岩型铀矿的成因认识、找矿勘查及选冶开采具有重要意义,但其矿物组成复杂,铀矿物粒度细小、种类繁多且赋存状态多样,致使研究初始的鉴定阶段就存在难点。目前普遍使用放射性照相法和电子探针(EMPA)两种方法开展铀矿物鉴定分析工作。放射性照相可一次性得到光片中所有铀矿物赋存位置、赋存状态和放射性形态,但无法鉴定矿物种类,耗时较长且需在暗室中进行;电子探针可得到铀矿物背散射图像和各元素含量,但在高倍数下薄片中寻找含量少、粒度小的铀矿物费时费力,并且在黑白背散射图像中无法快速判断伴生矿物种类。本文以鄂尔多斯盆地北缘-南缘-西缘砂岩型铀矿为研究对象,将自动矿物分析系统(AMICS)运用于砂岩型铀基础研究中,结合扫描电镜(SEM)、能谱仪(EDS)鉴定出研究区铀矿物有铀石、晶质铀矿、沥青铀矿和硅钙铀矿,黄铁矿和钛氧化物与铀矿物关系密切,识别出其他伴生矿物还有石英、金红石、长石、云母、高岭石等。本文建立的AMICS-SEM-EDS分析方法,实现了铀矿物及其共生矿物组合的快速识别鉴定和赋存状态研究。

Application of Automatic Mineral Analysis Technology to Identify Minerals and Occurrences of Elements in Sandstone-type Uranium Deposits in the Ordos Basin

BACKGROUND: The Ordos Basin is one of the most important areas in China because it hosts lots of sandstone-type uranium deposits and a variety of other energy and mineral resources. The occurrence of uranium minerals is of great significance to the genetic understanding and prospecting of sandstone-type uranium deposits. However, the complex mineral composition, fine grain size, and various types and occurrences of uranium minerals make the initial identification stage of the study difficult. Currently, radiograph and electron probe microanalysis (EMPA) have played an important role in the identification of uranium minerals. Radiography can be used to obtain the position, occurrence and radioactive form of all uranium minerals in the light film at one time, but the mineral type cannot be identified. Moreover, it is a lengthy process and must be performed in darkness. Electron probe can be used to obtain the backscattered image of the uranium mineral. However, it takes time and effort to find uranium minerals with small content and small particle size in thin slices at high magnification, and it is impossible to quickly determine the types of associated minerals in BSE images.
OBJECTIVES: To find a more rapid and accurate method for identifying uranium minerals.
METHODS: The automatic mineral analysis system (AMICS), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) were used to identify minerals from sandstone-type uranium deposits in the north, south, and west margins of the Ordos Basin.
RESULTS: The minerals in the study were identified as coffinite, pitchblende, uraninite and uranophane. Pyrite and titanium oxide were closely related to uranium minerals, and other associated minerals were identified as quartz, rutile, feldspar, mica and kaolinite.
CONCLUSIONS: AMICS-SEM-EDS in situ analysis technology proves to be a reliable method for the rapid identification of uranium minerals, associated minerals, and their occurrences.