海拉尔盆地克鲁伦凹陷伊敏组绿泥石特征及其与铀成矿关系

CHARACTERISTICS OF CHLORITE IN THE YIMIN FORMATION AND ITS RELATIONSHIPWITHURANIUM MINERALIZATIONINTHE KELULUN SAG,HAILAR BASIN

克鲁伦凹陷含矿目的层伊敏组铀矿化与绿泥石关系密切。本次研究针对克鲁伦凹陷伊敏组中灰白色砂岩、灰绿色砂岩和灰色砂岩的绿泥石开展岩相学和电子探针原位微区分析,旨在查明绿泥石特征及其与铀矿化关系。通过化学定量分析确定了绿泥石种类并大致确定其形成条件,在此基础上探讨了不同种类绿泥石性质及其与铀成矿关系。结果显示,研究区绿泥石可以分为孔隙充填型和黑云母蚀变型。Fe-Si图解表明伊敏组中灰色砂岩和少量灰白色砂岩中绿泥石主要为蠕绿泥石,多数灰白色砂岩和个别灰绿色砂岩中绿泥石为密绿泥石,少数灰白色砂岩和灰绿色砂岩中绿泥石为铁斜绿泥石。根据Mg/(Fe+Mg)-Al/(Al+Fe+Mg)关系图解确定不同颜色中绿泥石主要来源于镁铁质流体,少量为泥质来源。依据经验公式计算所得灰白色砂岩的绿泥石形成温度为150~170℃;灰绿色砂岩的绿泥石形成温度为150~180℃;灰色砂岩的绿泥石形成温度为170~200℃,结合绿泥石中主要阳离子与镁的关系图解共同确定出绿泥石是由多期次的中低温热液流体作用产物。与铀成矿有关的灰色砂岩中绿泥石较灰白色砂岩和灰绿色砂岩的绿泥石形成于更还原环境,其形成机制包括溶蚀-结晶和溶蚀-迁移-结晶两种方式。绿泥石化过程以及与绿泥石形成有关的热液作用既能够促进了铀的活化迁移,也促进了铀的吸附沉淀。

In this study,chlorite within the grayish white,grayish green,and gray sandstone layers of the uranium-bearing Yimin Formation in the Kelulun Depression is examined using petrographic and in-si-tu electron microprobe analysis techniques to understand its characteristics and its relationship with urani-um mineralization.Chemical quantitative analysis is employed to investigate the types and forming condi-tions of chlorite,and its properties and connection with uranium mineralization are discussed.The results reveal two main types of chlorite:pore filling type and biotite alteration type.Based on Fe-Si diagrams,chlorite in the gray sandstone and some grayish-white sandstone is predominantly vermiculite,while most grayish-white and some grayish-green sandstone contain miculite,and a few samples of both grayish-white and grayish-green sandstone contain ferroclinochlorite.Result of the Mg/(Fe+Mg)-Al/(A1+Fe+Mg)relationship indicates that chlorite in different colors primarily originates from mafic fluid sources,with a minor contribution from argillaceous fluids.The empirical formula suggests chlorite formation tempera-tures ranging from 150 to 170℃ for grayish white sandstone,150 to 180℃ for grayish-green sandstone,and 170 to 200℃ for gray sandstone.Relationship diagrams between main cations and magnesium in chlo-rite confirm its formation through multi-stage hydrothermal fluid interactions.Chlorite associated with u-ranium mineralization in gray sandstone forms under more reducing conditions compared to grayish white and grayish green sandstone.Its formation mechanism involves dissolution-crystallization and dissolution-migration-crystallization processes.These chlorite processes and hydrothermal actions contribute to the activation,migration,adsorption,and precipitation of uranium.