六二一七热液铀矿床形成的物理化学条件研究

PHYSICO-CHEMICAL CONDITIONS OF MINERALIZATION IN No. 6217 GRANITE-TYPE URANIUM DEPOSIT

根据包裹体分析资料和热力学计算结合矿床地质特征，本文研究了江西六二一七花岗岩型铀矿床形成的物理化学条件，并对红化（赤铁矿化）与热液铀矿化之间的因果关系进行了探讨。结果得到，热液铀矿化形成于中低温、中压、低氧逸度、高流逸度、中性至弱碱性的还原环境。成矿热液中，铀主要呈［UO2（CO3）2］2-和［UO2F4］2-形式迁移，至一定的物理化学条件下发生沥青铀矿沉淀。红化是矿前期高氧逸度流交代热液对围岩氧化所至，红化蚀变岩石因含有Fe3+，从而有利于热液铀矿化的发生。

Physico-chemical conditions of formation of the No. 6217 granite-type uranium deposit inJiangxi Province are investigated in terms of fluid inclusion data and thermodynamic calculations incombination with known geolegical features. The relationship between reddening (hematitization)and uranium mineralization is discussed as well. The results show that the mineralization wouldtake place under the conditions of meso- to low-temperatures, medium-pressure, low oxygen fugacity',high sulfur fugacity, and mediuw to weak alkaline, reducing environment. In the ore-bearingfluid , uranium would be transported dominantly in the form of [UO2 (CO3)2]2- and [UO2F4]2-, Thereddening could result from oxidation of the high-fo2 alkaline metasomatic fluid in pre-ore stagetothe ambient granites. The reddening rocks would provide a suitable redox condition, whereby theuranium in the fluid could be reduced to deposit pitchblende.