skip to main content


Title: Hydrothermal transport, deposition, and fractionation of the REE: Experimental data and thermodynamic calculations

For many years, our understanding of the behavior of the REE in hydrothermal systems was based on semi-empirical estimates involving extrapolation of thermodynamic data obtained at 25 °C. Since then, a substantial body of experimental data has accumulated on the stability of aqueous complexes of the REE. These data have shown that some of the predictions of Haas et al. (1995) are accurate, but others may be in error by several orders of magnitude. However, application of the data in modeling hydrothermal transport and deposition of the REE has been severely hampered by the lack of data on the thermodynamic properties of even the most common REE minerals. The discrepancies between the predictions and experimental determinations of the thermodynamic properties of aqueous REE species, together with the paucity of data on the stability of REE minerals, raise serious questions about the reliability of some models that have been proposed for the hydrothermal mobility of these critical metals. In this contribution, we review a body of high-temperature experimental data collected over the past 15 years on the stability of REE aqueous species and minerals. Using this new thermodynamic dataset, we re-evaluate the mechanisms responsible for hydrothermal transport and deposition of themore » REE. We also discuss the mechanisms that can result in REE fractionation during their hydrothermal transport and deposition. Here, our calculations suggest that in hydrothermal solutions, the main REE transporting ligands are chloride and sulfate, whereas fluoride, carbonate, and phosphate likely play an important role as depositional ligands. In addition to crystallographic fractionation, which is based on the differing affinity of mineral structures for the REE, our models suggest that the REE can be fractionated hydrothermally due to the differences in the stability of the LREE and HREE as aqueous chloride complexes.« less
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. McGill Univ., Montreal, QC (Canada)
  3. Monash Univ., Melbourne, VIC (Australia)
Publication Date:
Report Number(s):
Journal ID: ISSN 0009-2541
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 439; Journal Issue: C; Journal ID: ISSN 0009-2541
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
Natural Sciences and Engineering Research Council of Canada (NSERC); USDOE
Country of Publication:
United States
58 GEOSCIENCES; earth sciences; hydrothermal; REE; transport; deposition; fractionation; rare earth elements
OSTI Identifier: