鄂尔多斯砂岩型铀矿床中灰绿色砂岩还原能力影响因素研究

Study on Influcing Factors for Reduction Capacity of Gray-Green Sandstone in Ordos Sandstone-type Uranium Deposits

层间氧化型砂岩型铀矿是一种具有实际工业意义的铀矿床,在还原环境下,铀相对难迁移,有利于铀矿床的储存。亚铁离子、硫离子、黄铁矿、有机质等物质都可能对砂岩型铀矿的还原环境发挥作用。为研究鄂尔多斯地区砂岩型铀矿U(Ⅵ)的还原因素,本文对砂岩型铀矿及大量存在的灰绿色砂岩常见的还原性物质亚铁离子、硫离子、黄铁矿、钛铁矿、腐殖酸、甲烷气、氢气对U(Ⅵ)进行了常温常压下的模拟实验,利用极谱法和分光光度法分别测定U(Ⅵ)和U(Ⅳ)的含量,进而分析它们的还原能力。结果表明:亚铁离子和硫离子具有较强的还原性,黄铁矿、钛铁矿和腐殖酸的还原作用甚微,氢气和甲烷气并不参与U(Ⅵ)反应;如10 g灰绿色砂岩经蒸馏水浸泡后,得到1.1~26μg/m L亚铁离子,没有检测出硫离子。说明灰绿色砂岩具有较强还原性的主要原因是其在地下水浸泡下产生的微量亚铁离子发挥作用,揭示了鄂尔多斯地区砂岩型铀矿大量存在的灰绿色砂岩是形成后生水成铀矿的最重要因素。

BACKGROUND： The reductive environment of uranium is the most important influencing factor of uranium mineralization. The study of various redox markers in interlayer oxidation bands is of great significance for finding interlayer oxidation zone sandstone-type uranium deposits.OBJECTIVES： The reduction experiments were carried out on reducing materials commonly found in sandstonetype uranium deposits such as ferrous,sulfide,pyrite,ilmenite,humic acid,biogas,and hydrogen. The reduction capacity of ferrous ion,sulfur ion,pyrite and other reduction factors at room temperature and pressure was studied.METHODS： By polarography and spectrophotometry experiments to determine U（ Ⅵ） and U（ Ⅳ） content respectively. Their reduction capacity was analyzed.RESULTS： Iron ion and sulfur ion had strong reducing properties,andhumic acid had certain reducing properties.Such as pyrite,ilmenite experiment in different acidity and sage green sandstone water soaking experiments showed that the soaked solution of gray-green sandstone contained a certain amount of ferrous ions,and there was no sulfur ion.CONCLUSIONS： These ferrous ions were the main reason for the strong reducibility of gray-green sandstone.It also indicated that the gray-green sandstone was one of the most important factors in the subsequent mineralization of sandstone type uranium deposit in Ordos area.