鄂尔多斯盆地巴音青格利铀矿床绿泥石特征及其与铀成矿的关系

Characteristics of chlorite and their relationship with uranium mineralization in the Bayinqinggeli uranium deposit of Ordos Basin

鄂尔多斯盆地东北部砂岩型铀矿床普遍发育绿泥石化,且与铀矿化关系密切。在详细岩心观察和室内岩相学研究基础上,利用电子探针分析技术对灰绿-绿色岩石中的绿泥石进行了微区化学成分研究,根据成分计算了绿泥石的特征值和形成温度等相关参数,并划分了绿泥石的化学类型,分析讨论了巴音青格利铀矿床灰绿色、绿色砂岩中绿泥石的形成机制及其在铀成矿过程中所起的作用。结果表明,巴音青格利铀矿床绿色砂岩中绿泥石主要为蠕绿泥石、密绿泥石和铁斜绿泥石,其绿泥石物质主要来源于镁铁质流体,形成温度主要位于140~190℃;灰绿色砂岩中的绿泥石主要为铁镁绿泥石、密绿泥石和铁斜绿泥石,其绿泥石物质主要来源于泥质岩石,形成温度主要集中于140~170℃。灰绿色和绿色砂岩中的绿泥石主要在还原环境中形成,其形成机制有两种:先溶解然后重结晶沉淀和先溶解然后异地结晶沉淀。灰绿色砂岩绿泥石化的过程以及与绿泥石形成有关的热液作用不仅促进了铀的活化转移,也促进了铀的吸附沉淀。

Chloritization is widely developed in sandstone-type uranium deposits in the northeastern Ordos Basin,and it is closely related to uranium mineralization.Based on the detailed core observation and laboratory petrographic study,the chemical composition of chlorite in grey-green rocks was studied by using electron probe analysis technique.According to the composition,the characteristic value and formation temperature of chlorite was calculated,and the chemical types of chlorite were classified.The formation mechanism of chlorite and its role in uranium mineralization in the grey-green and green sandstones in Bayinqinggeli uranium deposit were discussed.The results showed that the chlorite in the green sandstone in Bayinqinggeli uranium deposit was mainly creep chlorite,pycnochlorite and iron plagiochlorite,and the chlorite materials are mainly derived from mafic fluid,and the formation temperature was mainly between 140℃and 190℃.The chlorite in gray-green sandstone was mainly ferromagnesia chlorite,pycnochlorite and Iron plagiochlorite.The chlorite materials were mainly derived from argillaceous rocks,and the formation temperature was mainly concentrated in the range of 140~170℃.Chlorite in grey-green and green sandstone was mainly formed in reductive environment,and there was two formation mechanism:one was first dissolved and then recrystallized precipitation,the other was first dissolved and then allochthonous crystallization precipitation.The process of chloritization of gry-green sandstone and the hydrothermal action related to the formation of chlorite not only promoted the activation and transfer of uranium,but also promoted the adsorption and precipitation of uranium.