华南诸广岩体中段含砷黄铁矿特征及其与铀成矿关系  

Characterization of Arsenic-Bearing Pyrite and the Relationship with Uranium Metallogenic in the Central Zhuguang Pluton,Southern China

作　　者：邹明亮 黄宏业 刘鑫扬 范立亭 向庭富 徐浩[3] 欧阳平宁 ZOU Mingliang HUANG Hongye LIU Xinyang FAN Liting XIANG Tingfu XU Hao OUYANG Pingning(Changsha Uranium Geology Research Institute, CNNC, Changsha, 410011 China Nuclear Geology, Beijing , 100013 Beijing Research Institute of Uranium Geology, CNNC, Beijing, 100029)

机构地区：[1]核工业二三0研究所,长沙410011 [2]中国核工业地质局,北京100013 [3]核工业北京地质研究院,北京100029

出　　处：《地质论评》2017年第4期1021-1039,共19页Geological Review

基　　金：中国核工业集团公司项目(编号:LTD1602,3210402)的成果~~

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。Objectives：Zhuguangshan pluton, located in the middle of the Nanling large igneous province in Southern China, is an important ore concentration area of granite-type uranium in China. Achievevments were mainly on pluton, fluids, tectonic, alteration and metallogenic prognosis, but little study about minerals genesis and the interrelation between them. This study focused on the characteristics of arsenic-bearing pyrite and its relationship with uranium mineralization. Methods：Thin section preparation and single mineral separation of pyrite were completed by Langfang Integrity Geological Service Co. Ltd. X-ray powder diffraction, X-ray photoelectron spectroscopy, Back scattered electron imaging（BSE） and electronic probe microanalysis were completed at the Modern Analysis and Test Center of Central South University. He—Ar isotopic and cathodeluminescence analysis were completed at the Analysis and Test Center of Beijing Research Institute of Uranium Geology, CNNC. X ray powder diffraction samples are pure pyrite grains selected from uranium ore, the samples were crushed to 100% passing 200 mesh at least and assayed at 40 kV, 40 mA, 2°/min and 0.02°/step using the Bruker produced D8 Advance diffractometer. Rietveld refinement was performed on diffraction patterns using Fullprof software, Rietveld method and Pseudo-Voigt model. Fe（S099As001）2 （ICSD：109376） structure was selected as the initial model. The refinement steps include scaling factor, zero correction, background, cell parameters, peak pattern parameters, temperature factor, atomic coordinate and site occupation, etc. DFT-based first-principle computation was performed by CASTEP software, with 2×2×2 super-cell applied. This energy convergence standard was 1.0×10-5 and the electron pole was small, so All bands/EDFT was used for the calculation. The ESCALAB 250Xi instrument was selected as a XPS model, the spot size was 200 μm, the analyser mode was CAE pass Energy, the voltage was 30.0 eV and the energy step length was 0.05 eV.

关 键 词：含砷黄铁矿 显微特征 矿物成因 硫还原作用 花岗岩型铀矿 诸广岩体 

分 类 号：P619.14[天文地球—矿床学]