华南诸广岩体中段含砷黄铁矿特征及其与铀成矿关系

发布时间：2018-05-04 12:03

本文选题：含砷黄铁矿 + 显微特征　；参考：《地质论评》2017年04期

【摘要】：诸广岩体中段位于南岭大火成岩省中部,为我国重要的花岗岩型铀矿矿集区。本次研究聚焦于含砷黄铁矿的特征及其与铀成矿关系,利用显微镜下光薄片鉴定、背散射电子成像、X射线光电子能谱、阴极发光、电子探针、He—Ar同位素及电子结构分析等技术方法研究了铀矿石中黄铁矿的微结构、地球化学特征及其还原铀的机理。分析表明,与沥青铀矿空间上存在伴生关系的黄铁矿为粒状含砷黄铁矿,其形成于铀成矿作用之前,在铀成矿期间释出S~-、Fe~(2+),且在主要铀成矿之后被硅质、次生铀矿物等交代。电子探针主微量元素及He—Ar同位素分析结果表明,与铀矿物有关的黄铁矿亏S富As,微量元素含量具有较大变化区间,富集Mo、Cu、Zn、Pb、Sb等,含砷黄铁矿具有相对较高的~3He值及n(~40Ar)/n(~36Ar)比值,形成于地壳流体占主导地位的壳幔混合流体。Rietveld结构精修及密度泛函理论计算获得的含砷黄铁矿电子结构特征表明,由于As元素的加入,S原子对费米能级附近的价带和导带均产生了贡献,活性非常大,是导致其还原铀的本质。基于上述认识及软硬酸碱原理,探讨了与碱、酸流体作用相关的"三阶段"铀成矿过程,认为早期铀成矿与含砷黄铁矿还原有关,晚期的富硅质流体对早期铀矿石起着交代和品位贫化的作用,最终导致了分形尺度上的铀成矿特征的不均一性。
[Abstract]:The middle section of the Zhuguang rock body is located in the middle of Nanling great igneous province, which is an important granitic uranium ore concentration area in China. The present study focused on the characteristics of arsenic-bearing pyrite and its relationship with uranium mineralization. It was identified by light slice under microscope, X-ray photoelectron spectroscopy (XPS) and cathodoluminescence (CL) were obtained by backscatter electron imaging. The microstructures, geochemical characteristics and mechanism of uranium reduction of pyrite in uranium ore have been studied by electron probe technique such as He-Ar isotope and electron structure analysis. The analysis shows that the pyrite associated with the asphaltene uranium deposit is granular arsenic-bearing pyrite, which was formed before uranium mineralization, and was replaced by siliceous and secondary uranium minerals during uranium mineralization. The results of electron probe main trace elements and He-Ar isotopic analysis show that pyrite is rich in As-rich in uranium, and the content of trace elements is in a large range, and the content of trace elements is enriched, such as Mo ~ (2 +) Cu ~ (2 +) Zn ~ (2 +) Pb ~ (2 +) SB, etc. The arsenic-bearing pyrite has a relatively high P _ 3He value and a ~ (40) Arn / n ~ (3 ~ (36) Ar) ratio. The electronic structure of arsenic-bearing pyrite obtained from the refined structure of crust and mantle mixed fluid. Rietveld structure formed in crustal fluid dominated by density functional theory shows that, Due to the addition of as to the valence band and conduction band near the Fermi energy level, the addition of as atoms is very active, which leads to the nature of the reduction of uranium. Based on the above understanding and the principle of soft and hard acid-base, the "three-stage" uranium mineralization process related to alkali and acid fluid interaction is discussed. It is considered that the early uranium mineralization is related to the reduction of arsenic-bearing pyrite. The late siliceous fluid plays an important role in the metasomatism and grade dilution of the early uranium ore, which leads to the heterogeneity of uranium metallogenic characteristics on fractal scale.
【作者单位】：核工业二三0研究所;中国核工业地质局;核工业北京地质研究院;
【基金】：中国核工业集团公司项目(编号:LTD1602,3210402)的成果~~
【分类号】：P619.14

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