地学前缘 ›› 2022, Vol. 29 ›› Issue (1): 42-53.DOI: 10.13745/j.esf.sf.2021.8.2

• 稀土金属矿床成矿机制与成矿模式 • 上一篇    下一篇

花岗岩风化壳中稀土纳米微粒的提取、表征及赋存状态研究

易泽邦1(), 付伟1,*(), 赵芹1, 许成1, 陆济璞2   

  1. 1.桂林理工大学 广西隐伏金属矿产勘查重点实验室, 广西 桂林 541004
    2.广西壮族自治区地质矿产勘查开发局, 广西 南宁 530023
  • 收稿日期:2021-04-21 修回日期:2021-07-02 出版日期:2022-01-25 发布日期:2022-02-22
  • 通信作者: 付伟
  • 作者简介:易泽邦(1990—),男,博士,主要从事纳米地球化学研究。E-mail: yizb@glut.edu.cn
  • 基金资助:
    国家自然科学基金重大研究计划培育项目(91962107);国家自然科学基金项目(42003066);国家自然科学基金项目(42173067);广西自然科学基金项目(2020GXNSFGA297003);广西自然科学基金项目(2019AC20007);广西自然科学基金项目(2019JJA150083)

Extraction, characterization and occurrence state of REE-bearing nanoparticles from granite-derived regolith

YI Zebang1(), FU Wei1,*(), ZHAO Qin1, XU Cheng1, LU Jipu2   

  1. 1. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China
    2. Guangxi Bureau of Geology & Mineral Prospecting & Exploitation, Nanning 530023, China
  • Received:2021-04-21 Revised:2021-07-02 Online:2022-01-25 Published:2022-02-22
  • Contact: FU Wei

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摘要：

研究风化壳中纳米微粒的稀土元素特征,对于从微观层面揭示我国华南风化壳型稀土矿床成因具有重要意义。以广西平南富稀土花岗岩风化壳剖面(ΣREEmax含量1 201 ×10-6)为典型案例,采用物理方法(超纯水,MQW)和化学方法(Na4P2O7, TSPP)两种技术手段,提取了花岗岩风化产物中的纳米微粒(1~100 nm)。进而采用中空纤维流场流分离-电感耦合等离子质谱仪联用技术(HF5-ICP-MS),对纳米微粒进行了连续分离和表征,同步获得了不同粒径纳米微粒中REE的含量特征。结果指示,化学提取剂TSPP能有效打破花岗岩风化产物中的大颗粒团聚体,它对纳米微粒的提取效率比物理提取方法高102~103倍。在TSPP提取的纳米微粒悬浮液中,REE含量(ΣREETSPP含量)最高可占到风化产物全岩REE总量(ΣREE含量)的80.5 %。纳米微粒主要分布于2~5 nm和10~30 nm两个粒径区间,另有少量粒径为30~80 nm的纳米微粒出现。其中,在2~5 nm微粒中,REE峰位与有机质大分子峰位对应,指示二者在离子键合作用下形成了聚合体。而在10~30 nm微粒中,REE峰位与Al元素峰位相对应,指示REE被黏土矿物纳米微粒吸附或离子交换。此外,本研究还发现轻稀土(LREE)与重稀土(HREE)在纳米微粒中的分布并不一致。其中以La、Ce、Pr和Nd为代表的LREE元素集中出现在2~5 nm和10~30 nm的纳米微粒中,而以Tb和Lu为代表的HREE元素除了在上述两个粒径的纳米微粒中有含量显示外,还分布于30~80 nm的纳米微粒中,指示了花岗岩风化产物中可能存在着相对独立的、与有机质和黏土矿物无直接关联的重稀土纳米微粒矿物。上述发现为进一步认识风化壳型稀土矿床中稀土元素的赋存状态和富集分异过程提供了新的启示。

关键词: 花岗岩风化壳, 稀土元素, 纳米微粒, 中空纤维流场流分离-电感耦合等离子质谱仪联用技术

Abstract:

Characterization of REE in nanoparticles extracted from regolith is important for revealing the genesis of regolith-hosted REE deposits in South China. In this study, we used both physical (MilliQ water, MQW) and chemical (Na4P2O7, TSPP) techniques to extract nanoparticles (1-100 nm) from the profile of REE-enriched granite-derived regolith in Pingnan, Guangxi. Hollow fiber flow field-flow fractionation and inductively coupled plasma mass spectrometer (HF5-ICP-MS) were used to separate and characterize the nanoparticles continuously from regolith and simultaneously obtain the particle size distribution. We show that the chemical dispersant can efficiently break up large-size nanoparticle aggregates and achieve much higher (102-103 times) extraction efficiency compared to the physical extraction method, with ~80.5% REE extracted from regolith. The particle size mostly ranged between 2-5 nm and 10-30 nm, and some between 30-80 nm. In 2-5 nm nanoparticles, the REE peak position was closely related to organic matter macromolecules, indicating the association of the two, via ionic interactions; whereas in 10-30 nm nanoparticles, the REE peak position was almost identical to Al element, indicating REE association with clay minerals, via adsorption or ion exchange. Furthermore, the size distributions of light (LREE) and heavy (HREE) REEs in nanoparticles differed. LREEs, represented by La, Ce, Pr and Nd, were mostly in 2-5 nm and 10-30 nm nanoparticles; whereas HREEs, represented by Tb and Lu, were also in 30-80 nm particles, indicating there are other HREE source besides clay mineral and organic matter from regolith. The findings of this study provide new insights into the occurrence states as well as enrichment/differentiation process of REEs in regolith-hosted REE deposits.

Key words: granite weathering regolith, REE, nanoparticle, hollow fiber flow field-flow fractionation coupled with inductively coupled plasma mass spectrometer (HF5-ICP-MS)

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