南岭中段黄沙铀矿区绿泥石成因及其与铀成矿关系

Genesis of chlorite in the Huangsha uranium deposit,middle part of Nanling Mountains and its relationship with uranium mineralization

绿泥石化是南岭中段黄沙铀矿区中广泛发育的热液蚀变类型。在岩相学的基础上,通过电子探针分析技术研究了铀矿区内221、223铀矿床绿泥石的矿物共生组合类型与形貌特征,划分了绿泥石的化学类型,提出该矿区绿泥石的4种产出状态,探讨了绿泥石的形成温度和环境,讨论了绿泥石的形成机制及其与铀成矿的关系。研究结果显示该矿区绿泥石:(1)在形貌特征上,矿前期绿泥石主要呈黑云母假象或星点状、团块状产出,成矿期绿泥石主要呈脉状产出;(2)在成因类型上,绿泥石主要有黑云母蚀变型、长石蚀变型、裂隙充填型和与铀矿共生型4种类型;(3)绿泥石的形成温度为200~310℃,其中与铀矿物共生型绿泥石的平均形成温度为215℃,属于中低温热液矿床范围;(4)绿泥石主要形成于还原环境,形成机制主要有溶解-沉淀和溶解-迁移-沉淀两种。

Chloritization is a type of hydrothermal alteration widely developed in the Huangsha uranium deposit in the middle part of the Nanling Mountains.Based on petrographic studies,the authors investigated the types and morphological characteristics of chlorite minerals in No.221 and No.223 uranium deposits by using electron microprobe analysis,and classified chemical types of chlorite.Four kinds of chlorite production status were recognized,and the temperature and environment of the formation of chlorite as well as the relationship between chlorite formation and uranium mineralization was discussed.The results are as follows:(1)The early chlorite was mainly of biotite pseudomorph or starlike shape characterized by mass output,and the metallogenic chlorite was mainly produced in the vein.(2)There are four types of genesis i.e.,chlorite biotite alteration,feldspar alteration,fracture filling type and uranium deposit association.(3)The chlorite-forming temperature was 200-310℃,and the average formation temperature of chlorite coexisting with uranium minerals was 215℃,suggesting a middle-low temperature hydrothermal deposit.(4)Chlorite was mainly formed in a reductive environment,and the formation mechanism was dissolution-precipitation and dissolutionmigration-precipitation.