【摘要】 本文通过光学显微镜鉴定、铁物相分析、电子探针分析、黄铁矿S同位素分析等手段,开展了铁元素矿物相和化学相特征研究及其成矿意义探讨。研究表明,本区砂岩中铁物相主要包括碳酸铁（菱铁矿）、硫化铁（黄铁矿）、铁氧化物（赤铁矿、褐铁矿、磁铁矿）以及铁硅酸盐（黑云母、绿泥石、绿帘石）,其中铁氧化物是直罗组砂岩中铁元素最主要的存在形式,硫化铁是矿化砂岩重要的指示矿物,上述两种铁物相均在矿化砂岩中含量最高;主要的铀矿物类型为铀石,与黄铁矿关系最为紧密,主要以"围绕"和"包含"的形式与黄铁矿相伴产出;黄铁矿的S同位素分布范围是-39.4‰～-8.5‰,表现出明显的富³²S、贫³⁴S的特点,指示了生物成因的特征;U/Th及δU的分布特征指示了二次还原砂岩经历了明显的氧化过程,矿化砂岩的还原性最强。铁物相的特征指示了纳岭沟铀矿床成矿过程的复杂性,既有早期的氧化改造,又有后期的二次还原改造,同时在成矿过程中还伴有硫酸盐还原菌等微生物的参与。黄铁矿作为铀成矿最敏感的指示矿物,是由无机还原反应叠加生物作用形成的。更多还原

【Abstract】 This paper studied the characteristics of mineral and chemical phases of ferrum in the Zhiluo Formation of the Nalinggou uranium deposit in the northern Ordos Basin and the geochemical behavior of ferrum minerals in uranium metallogenesis process.The characteristics of mineral and chemical phases of ferrum and their metallogenic significance were investigated by means of optical microscopy identification,ferrum phases analysis,EPMA and pyrite S isotope analysis and so on,.The study shows that the ferrum phases in the sandstone include FeCO₃（siderite）,FeS₂（pyrite）,ferric oxide（hematite,limonite,magnetite）and ferric silicate（Biotite,chlorite and epidote）,of which ferrum oxide is the most important form of Fe in sandstone of the Zhiluo Formation,and FeS₂ is an important indicative mineral of mineralized sandstone.Mineralized sandstone has the highest contents of ferrum oxide and FeS₂.The main uranium mineral in this area is coffinite,which has the closest relationship with pyrite,and occur mainly with pyrite in the form of "encirclement"and "inclusion".Pyrite has δ³⁴S_V-CDTvalues from -39.4‰ to -8.5‰,showing the obvious enrichment of ³²S and the depletion of ³⁴S,indicating the characteristics of biogenic processes.The distribution characteristics of U/Th andδU indicate that the secondary reduced sandstone underwent obvious oxidation process and the reduction of mineralized sandstone was strongest.The characteristics of ferrum phases indicate the complexity of the metallogenic process of the Nalinggou uranium deposit,which not only includes the early oxidation and the later secondary reduction,but also involvement of microorganisms such as sulfate-reducing bacteria in the metallogenic process.Pyrite,the most sensitive indicator of uranium mineralization,was formed by the superposition of inorganic reduction and biological action.更多还原