风化壳中不同种类黏土矿物对离子态稀土元素富集的贡献——以帽峰山风化剖面为例  

Influence of Clay Minerals on Rare Earth Element Enrichment in Weathering Crusts:A Case Study of the Maofeng Weathering Profile

作　　者：徐洁 黄伟光[4] 王高锋 徐永进 魏景明 朱建喜[1,2,3] 何宏平 XU Jie;HUANG Weiguang;WANG Gaofeng;XU Yongjin;WEI Jingming;ZHU Jianxi;HE Hongping(CAS Key Laboratory of Mineralogy and Metallogeny,Guangdong Provincial Key Laboratory of Mineral Physics and Materials,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Rising Nonferrous Metals Co.,Ltd,Guangzhou 510610,Guangdong,China)

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/广东省矿物物理与材料研究开发重点实验室,广东广州510640 [2]中国科学院深地科学卓越创新中心,广东广州510640 [3]中国科学院大学,北京100049 [4]广晟有色金属股份有限公司,广东广州510610

出　　处：《大地构造与成矿学》2024年第2期270-282,共13页Geotectonica et Metallogenia

基　　金：广东省基础与应用基础研究重大项目(2019B030302013);广东省科技创新领军人才项目(2019TX05L169)联合资助。

摘　　要：在离子吸附型稀土矿床中,黏土矿物被认为是可交换离子态稀土元素的主要载体。高岭石和埃洛石是风化壳中富集稀土元素的主要黏土矿物,高岭石和埃洛石属同族矿物,结构相似,互为多型,由于常规方法无法准确区分高岭石和埃洛石的矿物组成和含量,从而无法准确区分各黏土矿物对稀土元素富集的贡献。本文以帽峰山风化剖面为研究对象,采用甲酰胺法处理风化壳样品,对风化壳中的高岭石和埃洛石进行半定量分析。并且,通过模拟吸附实验,查明了各类黏土矿物对稀土离子的吸附特征和吸附量,并结合等温吸附模型,揭示了黏土矿物对稀土离子的吸附机理。进一步通过理论计算,量化了各类黏土矿物对风化剖面不同深度稀土元素富集的贡献。结果表明,全风化层稀土元素富集的主要贡献矿物是高岭石,全风化层下部和表土层稀土元素富集的主要贡献矿物是埃洛石,半风化层稀土元素富集的贡献矿物同时包括高岭石、埃洛石和伊利石。本文半定量分析了风化壳中高岭石和埃洛石的矿物组成,量化了各类黏土矿物对风化壳各层稀土元素富集的贡献作用,厘清了各类黏土矿物对稀土离子的吸附机理,为进一步认识风化壳中稀土元素富集机制奠定理论基础。In ion-adsorption rare earth deposits,rare earth elements(REE)are adsorbed on clay minerals,predominantly on kaolinite and halloysite.However,because of their similar structures,accurate and quantitative distinction of kaolinite and halloysite by conventional methods is unlikely.Thus,the contribution of various clay minerals to REE enrichment cannot be accurately determined.In this study,we semi-quantitatively distinguish the compositions of kaolinite and halloysite in a Maofeng weathering crust using formamide treatment.We compared the adsorption capacities of various clay minerals for REE using simulated adsorption experiments.Combined with the isothermal adsorption model,the REE adsorption mechanism of clay minerals is revealed.Furthermore,the contribution of various clay minerals to REE enrichment at different depths of the weathering profile is quantified through theoretical calculations.The results suggest that kaolinite contributes the most to REE enrichment in the fully weathered regolith layer,halloysite contributes the most to REE enrichment in the semi-weathered regolith layer and the topsoil layer,and kaolinite,halloysite,and illite contribute to REE enrichment in the semi-weathered regolith layer.This work semi-quantitatively distinguishes the mineral compositions of halloysite and kaolinite,providing an easy method for the mineralogy quantitative analysis of weathering crusts.It also quantifies the contribution of various clay minerals to REE enrichment in weathering crusts,which advances our understanding of the REE enrichment mechanism in weathering crusts.

关 键 词：离子吸附型稀土 富集 黏土矿物 高岭石 埃洛石 

分 类 号：P574[天文地球—矿物学] P595[天文地球—地质学]