Affiliation:
1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
2. CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Guangzhou 510640, China
3. University of Chinese Academy of Sciences, Beijing 100101, China
Abstract
Rare earth elements (REEs) have recently been classified as critical and strategic metals due to their importance in modern society. Research on the geochemical behaviors and mineralization of REEs not only provides essential guidance for mineral exploration but also holds great significance in enhancing our understanding of Earth’s origin and evolution. This paper reviews recent research on the occurrence characteristics, deposit types, and hydrothermal behaviors of REEs, with a particular focus on comparing the complexation and transport of REEs by F, Cl, S, C, P, OH, and organic ligands in fluids. Due to the very weak hydrolysis of REE ions, they predominantly exist as either hydrated ions or free ions in low-temperature and acidic to weakly basic fluids. As the ligand activity increases, the general order of transporting REEs is Cl− ≈ SO42− > F− ≈ PO43− > CO32− > OH− under acidic conditions or OH− > SO42− ≈ Cl− > F− under alkaline conditions. In acidic to neutral hydrothermal systems, the transport of REEs is primarily dominated by SO42− and Cl− ions while the deposition of REEs could be influenced by F−, CO32−, and PO43− ions. In neutral to alkaline hydrothermal systems, REEs mainly exist in fluids as hydroxyl complexes or other ligand-bearing hydroxyl complexes. Additionally suggested are further comprehensive investigations that will fill significant gaps in our understanding of mechanisms governing the transport and enrichment of REEs in hydrothermal fluids.
Funder
the Guangdong Major Project of Basic and Applied Basic Research
the Strategic Priority Research Program of the Chinese Academy of Sciences
GIGCAS
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