棉花坑铀矿床绿泥石矿物学特征及其地质意义

Mineralogical Characteristics of Chlorite and its Geological Significance to Mianhuakeng Uranium Deposit

绿泥石作为棉花坑铀矿床重要的蚀变矿物,且主要以4种形态产出。运用电子探针技术分析了绿泥石的化学成分,研究结果显示,绿泥石主要为富铁蠕绿泥石、铁镁绿泥石,形成于还原环境;不同成因和产状的绿泥石绝大部分来源于泥质岩,少数绿泥石来源于铁镁质岩;绿泥石的形成温度介于187~297℃之间,形成机制主要为溶蚀-沉淀结晶及溶蚀-迁移-沉淀结晶两类。赋矿花岗岩在发生绿泥石化时,将岩体中的铀进一步活化形成活性铀,促进后期铀的迁移,此外,绿泥石作为富Fe的层状硅酸盐矿物,为流体中铀的沉淀、富集提供了良好的还原性环境。

Chlorite is an important alteration in Mianhuakeng uranium deposit.The mineralogical characteristics of chlorite suggested that there were four main occurrence forms.The chemical composition of chlorite was studied by electron probe analysis.The results showed that chlorite was mainly iron rich peristaltic chlorite and ferromagnesium chlorite,which formed in the reduction environment.The chlorite of different origin and occurrence mostly comes from argillaceous rock,a few chlorite comes from magnesite,and the formation temperature of chlorite was between 187℃and 297℃,Dissolution precipitation crystallization and dissolution migration precipitation crystallization are two important mechanisms of chloritization.In addition,chlorite is a Fe-rich layered silicate mineral,which provides a good reducing environment for uranium precipitation and enrichment in fluids.