离子吸附型稀土矿床形成的矿物表/界面反应机制  

Mineral surface reaction constraints on the formation of ion-adsorption rare earth element deposits

作　　者：梁晓亮[1,2] 谭伟[1,2] 马灵涯 朱建喜[1,2] 何宏平[1,2] LIANG Xiaoliang;TAN Wei;MA Lingya;ZHU Jianxi;HE Hongping(Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Key Laboratory of Mineral Physics and Materials of Guangdong Province,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Ch)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [2]中国科学院广州地球化学研究所广东省矿物物理与材料研究开发重点实验室,广东广州510640

出　　处：《地学前缘》2022年第1期29-41,共13页Earth Science Frontiers

基　　金：广东省基础与应用基础研究重大项目(2019B030302013);中国科学院地质与地球物理研究所重点部署项目(IGGCAS-201901);广州市科技计划重点项目(201804020037);国家自然科学基金项目(41921003,41773113,41702041,42022012)。

摘　　要：华南离子吸附型稀土矿床提供了全球超过90%的重稀土,是我国优势的战略性关键金属矿产资源。掌握这类矿床的成矿机制和禀赋特征,可为增加稀土资源储量和高效利用稀土资源提供理论支撑。离子吸附型稀土矿床主要发育在富稀土花岗岩、浅变质岩及火山岩的风化壳中。基岩中的(含)稀土矿物是风化壳中离子态稀土的主要来源,其矿物组合很大程度上决定了稀土矿床的禀赋和分异特征。在物理-化学风化和微生物作用下,造岩矿物、含稀土矿物和稀土独立矿物逐渐溶解,使稀土元素活化和再富集。一方面,母岩风化形成的黏土矿物和铁锰氧化物具有较大的比表面积和一定的表面电荷密度,是稀土离子的主要载体;另一方面,稀土离子通过离子交换、表面吸附与络合、共沉淀,以及形成次生稀土矿物等途径富集在次生矿物表面,其富集-分异特征和赋存状态受矿物类型、pH、微生物活动等因素所控制。利用高分辨透射电镜结合选区电子衍射和电子能量损失谱,以及同步辐射X射线吸收精细结构谱,有望在原子级尺度查明稀土的微观赋存状态。未来研究需更多关注基岩中(含)稀土矿物组合及其演化路径的制约因素、微生物风化对离子吸附型稀土矿床成矿作用的约束,以及稀土元素的微观赋存状态等问题。The ion-adsorption rare earth element(IAR)deposits in South China produce more than 90%of the world’s heavy rare earth elements(HREEs).They are a key strategic metal resource of China.Thus,a better understanding of the metallogenic mechanism and resource characteristics of IAR deposits can provide a theoretical basis for increasing REE reserves and better utilization of REE resources.The IAR deposits are mainly developed in the weathering crusts of REE-rich granite,epimetamorphic and volcanic rocks.The REE-bearing minerals in protolith are the main sources of REE cations in weathering crust,where mineral association greatly determines the concentration and fractionation characteristics of REEs.Under physical/chemical weathering and microbial action,the dissolution of rock-forming minerals,REE-bearing minerals and REE minerals results in the activation and re-enrichment of REEs.On one hand,weathering of protolith produces clay minerals and Fe-Mn(hydr)oxides with a large specific surface area and high surface charge density.On the other hand,these secondary minerals can adsorb REE cations via ion exchange,surface adsorption/complexation or formation of secondary REE minerals.The adsorption mechanism,enrichment-fractionation characteristics and occurrence state of REEs are affected by mineral types,pH and microbial activity.By using high-resolution transmission electron microscopy(HRTEM)coupled with selected area electron diffraction(SAED)and electron energy loss spectroscopy(EELS)and synchrotron radiation X-ray absorption fine structure spectroscopy(XAFS),the atomic occurrence state of REEs can be determined.In the future,more attention should be paid to research areas including the association of REE-bearing minerals in protoliths and its evolutionary pathway and mechanism,the constraints of microbial weathering on the formation of IAR deposits,and the microscopic occurrence state of REEs.

关 键 词：离子吸附型稀土矿床 矿物溶解 矿物演化 稀土元素富集-分异 微生物风化 矿物表/界面反应 

分 类 号：P618.7[天文地球—矿床学] P595[天文地球—地质学]