甘肃龙首山碱交代型铀矿床绿泥石特征及意义

绿泥石化是龙首山铀矿床重要的蚀变类型之一。通过对龙首山碱交代型铀矿床的绿泥石等蚀变矿物进行的岩相学和电子探针成分分析研究，确定了龙首山地区绿泥石的化学类型主要为铁镁绿泥石，少数为蠕绿泥石。依据绿泥石成因或与共生矿物的关系，绿泥石可被划分为黑云母蚀变型、长石蚀变型、沥青铀矿共生型和副矿物共生型等4种类型。泥质岩是本区绿泥石的主要原岩类型，是多期次地质作用形成的产物。研究认为，龙首山地区碱交代型铀矿床的成矿过程可表述为矿前期在相对较高温度的热液流体作用下，黑云母发生绿泥石化蚀变，随后热液继续交代长石，形成长石蚀变型绿泥石，进而在成矿期热液温度相对较低的条件下形成与沥青铀矿紧密共生的绿泥石。绿泥石在铀成矿过程中不但活化了花岗岩里的铀，而且还给铀矿化供应了相对良好的积淀环境。

Characteristics and significance of chlorite in the Longshoushan alkali-metasomatic type uranium deposit

Chloritization is one of the most important alteration types in the Longshoushan uranium deposit. Based on EPMA analysis and mineralogical study of the chlorites in the Longshoushan uranium deposit, the authors found that the chemical types of chlorite in Longshoushan area is mainly mafic chlorite, with a small amount of ripidolite. Based on the genesis or the relationship with coexisting minerals of chlorite, the authors divide the chlorites into four types, i.e., biotite alteration type, feldspar alteration type, pitchblende association type and accessory mineral association type. Argillaceous rock is the main protolith of chlorite, which is the product of multi-stage geological activities. Studies show that the uranium mineralization process of the Longshoushan alkali-metasomatic type uranium deposit experienced different temperatures at different stages: At first, the hydrothermal solution was of high temperature and resulted in the chloritization of biotite, and then the metasomatism of feldspar formed chlorite of feldspar alteration type. At the mineralization stage, the hydrothermal solution was of low temperature and formed chlorite closely associated with pitchblende. In the process of uranium mineralization, chlorite not only activated uranium in the granite but also offered a favorable deposition environment.