μ-XRF技术在黄龙铺钼(铀)矿床铀矿物学研究中的应用

张熠阳; 钟福军; 杜景勇; 严杰; 潘春蓉; 黄卉; 康清清; 潘家永

doi:10.15898/j.cnki.11-2131/td.202105260067

μ-XRF技术在黄龙铺钼(铀)矿床铀矿物学研究中的应用

Application of μ-XRF in Uranium Mineralogy of the Huanglongpu Carbonate-type Molybdenum Deposit, Shaanxi Province, China

摘要

摘要: 东秦岭碳酸岩型钼成矿带是全球最大的钼成矿带。该带内的黄龙铺矿床是中国最早发现的碳酸岩型钼矿床之一。最近的野外地质调查发现，部分钼矿石具有较高的放射性异常，但其放射性元素的赋存形式和矿物学特征尚不明确。本文借助聚毛细管微束X射线荧光光谱分析（μ-XRF）分析速度快、原位无损、高灵敏度的分析优势，快速查明铀矿物的空间位置，再结合扫描电镜分析（SEM）和X射线能谱分析（EDS），确定铀矿物的种类及其次生变化。研究表明：黄龙铺矿床高放射性矿石中主要的铀矿物为钛铀矿、铌钛铀矿和晶质铀矿，它们与方解石、长石、黄铁矿、辉钼矿和黄铜矿呈共生关系。矿石中铀矿物后期均遭受氧化性流体改造，发生了明显的蚀变，钛铀矿蚀变之后转变为含Nb的钛铁氧化物，铌钛铀矿和晶质铀矿蚀变后矿物内部形成大量空洞，流体来源可能为大气降水。背散射电子（BSE）图像上灰度差异明显，暗示着矿物中元素分布的不均一性。

Abstract:
BACKGROUNDThe carbonatite-type molybdenum metallogenic belt in East Qinling is the largest molybdenum metallogenic belt in the world. The Huanglongpu deposit is one of the earliest discovered carbonatite-type molybdenum deposits in China. Our field survey found that the uranium grade of ores in this deposit was higher than the industrial uranium grade, being similar to the Huayangchuan U-Nb-Pb-REE deposit in the Qinling Orogenic Belt. However, the occurrences and mineralogical characteristics of radioactive elements are still unclear.
OBJECTIVESTo explore the main mineral assemblages, U occurrences and other characteristics of uranium ores in the Huanglongpu deposit.
METHODSThe detailed geological survey, μ-XRF, SEM and EDS analyses were carried out on the high-radioactivity ore from the Huanglongpu deposit.
RESULTSThe results showed that major uranium minerals in the Huanglongpu deposit were brannerite, betafite and uraninite, which were associated with calcite, feldspar, pyrite, molybdenite and chalcopyrite. Significant alteration and replacement of uranium minerals were observed in the studied ore sample. The betafite was transformed into Nb-rich Ti-Fe oxides after alteration. After alteration of brannerite and uraninite, a large number of cavities were formed within those minerals. The post-ore fluids were possible from meteoric water. The textural differences of altered brannerite and uraninite on BSE images suggested the variable chemical composition.
CONCLUSIONSμ-XRF technology has a great application prospect in the future research of uranium deposit genesis and prospecting prediction.

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