相山铀矿田云际矿床绿泥石特征及其地质意义

Characteristics of Chlorite in Yunji Deposit of Xiangshan Uranium Ore-field and Its Geological Implication

云际铀矿床是相山矿田典型的碱交代型矿床,其围岩和矿石中的绿泥石与铀矿化关系密切。笔者在详细的岩矿鉴定基础上,利用电子探针分析了绿泥石的化学成分特征,探讨绿泥石的形成环境及其地质意义。研究表明,该矿床的绿泥石可以分为黑云母假象型和填隙型两种产出形态,均属于相对富铁的铁镁绿泥石和密绿泥石,指示其形成于相对的还原环境中;绿泥石的形成温度为188~244℃,均值为213℃,属于中低温热液作用范围;从矿前期到成矿期,绿泥石表现出逐渐由Mg取代Fe的特征,暗示热液流体有向碱性方向的演化趋势;绿泥石主要有溶蚀-结晶和溶蚀-迁移-结晶两种形成机制。

Yunji deposit is a typical alkali metasomatic uranium deposit in Xiangshan ore-field,and the chlorites are closely related to uranium mineralization.Based on detail mineralogical observation,the chemical composition of chlorite was analyzed with electron microprobe.The forming environment of chlorite and its geological significance were discussed and concluded.Chlorites in Yunji deposit can be divided into chlorite altered from biotite and chlorite growing along cracks and microfractures.The both belong to iron rich femic chlorite and pycnochlorite which indicate that they are formed in a relatively reduced environment.The chlorite was formed in the temperature from 188 to 244℃with average of 213℃,fall in the meso-thermal-epithermal range.From pre-ore formation stage to ore formation stage,Fe in chlorite was tend to be replaced by Mg which suggest that the hydrothermal fluid gradually become relatively more alkaline.The formation of chlorite was believed mainly by the mechanism of dissolution-crystallization and dissolution-migration-crystallization.