The experimental determination of REE partition coefficients in the water-calcite system

Martin Voigt, Vasileios Mavromatis, Eric H. Oelkers

Research output: Contribution to journalArticleResearchpeer-review

Abstract

To better quantify the behaviour of rare earth elements (REE) in low temperature natural systems, calcite was precipitated from NaCl-bearing aqueous solutions in the presence of La and Yb using a constant addition technique at pH ~ 6 and 25 °C under steady-state conditions. The presence of REE in the fluid significantly slows calcite growth rates. Partition coefficients (DREE), determined from analysis of the aqueous solution compositions, range from 102.8 at the lowest aqueous La concentration to 101.4 at the highest aqueous concentration of Yb. DREE was found to correlate with aqueous REE concentrations, as well as with the calcite saturation state. Experimental results, together with previous spectroscopic evidence, suggest the incorporation of REE3+ into the Ca2+ site of calcite while maintaining charge balance by the concurrent incorporation of Na+. The value of the equilibrium constants for the corresponding exchange reaction was determined for La, Eu and Yb by combining our results with previously published experimental data. Subsequently, these constants were used together with a lattice strain model to estimate corresponding values for the other REE. Application of this exchange model suggests that DREE vary significantly with the composition of natural waters including seawater. Such variations are likely the origin for the large differences of DREE values reported in the literature based on experimental and field evidence.

Original languageEnglish
Pages (from-to)30-43
Number of pages14
JournalChemical Geology
Volume462
DOIs
Publication statusPublished - 25 Jun 2017

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Calcium Carbonate
Rare earth elements
partition coefficient
rare earth element
calcite
Water
Bearings (structural)
aqueous solution
water
Equilibrium constants
Chemical analysis
Seawater
saturation
seawater
Fluids
fluid
Temperature
incorporation

Keywords

  • Calcite
  • Co-precipitation
  • Rare earth elements
  • Trace element partitioning

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

Cite this

The experimental determination of REE partition coefficients in the water-calcite system. / Voigt, Martin; Mavromatis, Vasileios; Oelkers, Eric H.

In: Chemical Geology, Vol. 462, 25.06.2017, p. 30-43.

Research output: Contribution to journalArticleResearchpeer-review

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