西藏邬郁盆地砂岩中铀矿化特征及形成机理探讨

Discussion on characteristics and formation mechanism of uranium mineralization in sandstone of Wuyu basin,Tibet

邬郁盆地砂岩中铀矿的发现填补了西藏冈底斯成矿远景带铀矿的空白,深入研究铀赋存状态对后期勘查工作具有重要的指导意义。文章详细阐述了邬郁盆地砂岩中铀矿化特征,应用薄片鉴定、α放射性照相、电子探针和化学分析方法联合研究砂岩中铀的赋存状态。铀主要以矿物铀石形式呈微小颗粒浸染状分布在碱性长石和黑云母之间,其次以吸附形式赋存在基质、矿物颗粒边缘以及有机质中,偶见有与草莓状黄铁矿共生的沥青铀矿。电子探针和化学分析显示富铀矿石中稀土元素明显高于贫铀矿石和围岩。含矿层砂岩热液蚀变较强,主要为碳酸盐化、绢云母化、金属硫化物化、沸石化。结果表明邬郁盆地砂岩中铀矿的形成是以热液作用为主,后期有淋积作用的参与。

Uranium deposit in sandstone of Wuyu basin was discovered for the first time in Gangdese metallogenic belt, Tibet. The understanding of uranium occurrence is of important guiding significance for the uranium exploration in the area. The paper expounds the characteristics of uranium mineralization in sandstone of Wuyu basin. Thin section analysis, ct radiography photo, electron probe analysis and chemical analysis were used to study the uranium occurrence in sandstone of Wuyu basin. Coffinite is the major u-bearing mineral which existed as a tiny particles disseminated between alkali feldspar, biotite, and the minor as adsorbing uranium in the matrix at the edge of mineral particles and organic matter. Uraninite is occasionally associated with framboidal pyrite. Electron microprobe and chemical analysis shew that REE are significantly higher in the uranium-rich ore than uranium depleted ore and wall rock. Hydrothermal alteration in the sandstone of hosting formation is strongly occurred as carbonatization, sericitization, metal sulfide and zeolitization. It is shown that hydrothermal process developed during the formation of uranium metalization in sandstone of Wuyu basin, but illuviation was participated in the late.