特殊地质样品中钼同位素分析的化学前处理方法研究  

Research on the Chemical Pretreatment for Mo Isotope Analysis of Special Geological Samples

作　　者：闻静 张羽旭[1] 温汉捷[1,2] 朱传威 樊海峰[1] WEN Jing;ZHANG Yu-xu;WEN Han-jie;ZHU Chuan-wei;FAN Hai-feng(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵州贵阳550081 [2]中国科学院大学,北京100049

出　　处：《岩矿测试》2020年第1期30-40,共11页Rock and Mineral Analysis

基　　金：国家自然科学基金项目(41573007,41503011)

摘　　要：Mo同位素的研究在地学领域应用广泛,它可以示踪Mo的全球循环、古海洋氧化还原条件、成矿过程、天体演化过程等。应用多接收电感耦合等离子体质谱法(MC-ICP-MS)分析Mo同位素比值前需对样品进行分离纯化,以富集Mo和去除Zr、Ru、Fe、Mn等干扰元素。处理某些Fe含量特别高且Ca含量也高的特殊地质样品(如含大量黄铁矿的钙质泥岩、钙质页岩等),若根据传统的阴阳离子交换树脂双柱法,需多次使用阳离子交换树脂分离Fe,步骤较繁琐且Mo回收率也会降低,而根据传统的阴离子交换树脂单柱法,使用1mol/L氢氟酸-0.5mol/L盐酸介质会产生较多CaF2沉淀影响分离纯化效果。针对此类特殊地质样品,本实验使用同一阴离子树脂柱(AG1-X8,100~200目)对样品进行两次淋洗,第一次使用6mol/L盐酸,第二次使用1mol/L氢氟酸-0.1mol/L盐酸和6mol/L盐酸。结果表明Mo的回收率>96%,干扰元素的去除效果好,尤其是Ru的去除率接近100%,比原方法提高了约12%。对实际样品进行实验的结果也显示,Mo的回收率和干扰元素的去除都符合要求,δ98/95Mo测定值与文献报道值一致。改进后的阴离子交换树脂单柱-二次淋洗法适用于Fe、Ca含量较高的特殊样品,降低了分析成本,也适用于绝大多数地质样品。BACKGROUND: Mo isotopes have been widely used in the field of geosciences. They can be used to trace the global cycle of Mo, paleoocean redox conditions, mineralization processes, and astronomical evolution. Before the analysis of Mo isotope by multi-collector inductivity coupled plasma-mass spectrometry(MC-ICP-MS), the samples must be pretreated to enrich Mo and remove the interference elements(Zr, Ru, Fe and Mn). According to the traditional anion-cation exchange resin double-column method, it is necessary to use a cation-exchange resin multiple times to separate Fe. The steps are more complicated and the Mo recovery will be reduced. According to the traditional anion-exchange resin single-column method, 1 mol/L hydrofluoride acid-0.5 mol/L hydrochloric acid medium will produce more CaF2 precipitation and affect the separation and purification results.OBJECTIVES: To develop a new method for managing Ca-bearing geological samples with high Fe content before Mo isotope analysis.METHODS: For such special geological samples, the same anionic resin column(AG1-X8, 100-200 mesh) was used to rinse the sample twice, the first time using 6 mol/L hydrochloric acid, and the second time using 1 mol/L hydrofluoride acid-0.1 mol/L hydrochloric acid and 6 mol/L hydrochloric acid.RESULTS: Results showed that Mo recovery was better than 96%, and the removal of the interference elements was good, especially the Ru removal rate, which was higher than the previous methods by 12%, up to 100%. The results of experiments on actual samples also showed that the recovery of Mo and the removal of interfering elements meet the requirements, and the measured values of δ98/95Mo were consistent with those reported in the literature.CONCLUSIONS: The improved anion exchange resin single-column elution method is suitable for special samples with high Fe and Ca content, which reduces the analysis cost and is applicable to most geological samples.

关 键 词：MO同位素 离子交换树脂法 化学前处理 高铁高钙地质样品 MC-ICP-MS 

分 类 号：O628[理学—有机化学] O657.63[理学—化学]