Structural state of rare earth elements in eudialyte-group minerals
| Autor: | Joerg Goettlicher, P. Gamaletsos, Kalotina Geraki, Ralph Steininger, A. Borst, Adrian A. Finch, Henrik Friis, Nicola J. Horsburgh |
|---|---|
| Přispěvatelé: | NERC, University of St Andrews. School of Earth & Environmental Sciences, University of St Andrews. Scottish Oceans Institute, University of St Andrews. St Andrews Isotope Geochemistry |
| Rok vydání: | 2019 |
| Předmět: |
Lanthanide
Technology Rare Earth Elements Coordination sphere 010504 meteorology & atmospheric sciences XAS high-field-strength elements NDAS Analytical chemistry chemistry.chemical_element Eudialyte ILIMAUSSAQ COMPLEX engineering.material MONT SAINT-HILAIRE 010502 geochemistry & geophysics 01 natural sciences ALKALINE COMPLEX High field strength elements Geochemistry and Petrology Partitioning models Eudialyte Group Materials CRYSTAL-STRUCTURE MINERALIZATION 0105 earth and related environmental sciences SOUTH GREENLAND IMPLICATIONS X-ray absorption spectroscopy Science & Technology SPECTROSCOPY GE Extended X-ray absorption fine structure Rare-earth element Yttrium eudialyte-group minerals Mineralogy REE EVOLUTION XANES Critical metals EXAFS chemistry Physical Sciences Lattice strain theory engineering ddc:600 Peralkaline igneous rocks GE Environmental Sciences |
| Zdroj: | Mineralogical magazine, 84 (1), 19–34 Borst, A M, Finch, A A, Friis, H, Horsburgh, N J, Gamaletsos, P N, Goettlicher, J, Steininger, R & Geraki, K 2020, ' Structural state of rare earth elements in eudialyte-group minerals ', Mineralogical Magazine, vol. 84, no. 1, pp. 19-34 . https://doi.org/10.1180/mgm.2019.50 |
| ISSN: | 1471-8022 0026-461X |
| Popis: | Eudialyte-group minerals (EGM) attract global interest as potential resources for high-field-strength elements (e.g. Zr, Nb, Ta, and rare-earth elements), i.e. critical materials for modern technologies. They are particularly valued for their relative enrichment in the most critical lanthanides, i.e. Nd and heavy rare earth elements (Gd–Lu). However, rare earth element (REE) substitution mechanisms into the EGM structure are still poorly understood. Light and heavyREEmay occupy different sites and there may be ordering and/or defect clustering in the structure. This study uses X-ray absorption spectroscopy to determine the structural state ofREEin EGM from prospective eudialyte-bearing complexes. YttriumK-edge and NdL3-edge spectra were collected as proxies for heavy and lightREE, respectively, and compared to natural and syntheticREE-bearing standards. Extended X-ray absorption fine structure data yield best fits for Y in six-fold coordination with Y–O distances of 2.24–2.32 Å, and a second coordination sphere comprising Fe, Na, Ca, Si and O at radial distances of 3.6–3.8 Å. These findings are consistent with dominant Y3+substitution for Ca2+on the octahedralM1 site in all the samples studied, and exclude preferential substitution of Y3+onto the smaller octahedralZsite or the large low-symmetryN4 site.Using lattice strain theory, we constructed relative partitioning models to predict site preferences of lanthanides we have not measured directly. The models predict that allREEare favoured on the Ca-dominantM1 site and that preferential partitioning of heavy over lightREEincreases in EGM containing significant Mn in theM1-octahedral rings (oneillite subgroup). Thus, the flatREEprofiles that make EGM such attractive exploration targets are not due to preferential partitioning of light and heavyREEonto different sites. Instead, local ordering of Mn- and Ca-occupiedM1 sites may influence the capacity of EGM to accommodate heavyREE. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|