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@article{1849059,
author = {Steciuk, Gwladys and Škoda, Radek and Dillingerová, Veronika and Plášil, Jakub},
article_number = {1},
doi = {http://dx.doi.org/10.2138/am-2021-7875},
keywords = {Vyacheslavite; crystal structure; chemical composition; electron-diffraction tomography; miscibility; rhabdophane; uranium deposits},
language = {eng},
issn = {0003-004X},
journal = {American Mineralogist},
title = {Chemical variability in vyacheslavite, U(PO4)(OH): Crystal-chemical implications for hydrous and hydroxylated U4+, Ca, and REE phosphates},
url = {https://pubs.geoscienceworld.org/msa/ammin/article-abstract/107/1/131/610326/Chemical-variability-in-vyacheslavite-U-PO4-OH?redirectedFrom=fulltext},
volume = {107},
year = {2022}
}
TY - JOUR
ID - 1849059
AU - Steciuk, Gwladys - Škoda, Radek - Dillingerová, Veronika - Plášil, Jakub
PY - 2022
TI - Chemical variability in vyacheslavite, U(PO4)(OH): Crystal-chemical implications for hydrous and hydroxylated U4+, Ca, and REE phosphates
JF - American Mineralogist
VL - 107
IS - 1
SP - 131-137
EP - 131-137
PB - Mineralogical Society of America
SN - 0003004X
KW - Vyacheslavite
KW - crystal structure
KW - chemical composition
KW - electron-diffraction tomography
KW - miscibility
KW - rhabdophane
KW - uranium deposits
UR - https://pubs.geoscienceworld.org/msa/ammin/article-abstract/107/1/131/610326/Chemical-variability-in-vyacheslavite-U-PO4-OH?redirectedFrom=fulltext
N2 - Particularly interesting chemical variability in the U4+ phosphate mineral vyacheslavite from Menzenschwand (Germany) has been discovered and investigated by means of electron-diffraction and micro-chemical methods. Suggested variability comprises the elevated contents of calcium and rare-earth elements (REEs or Ln). Based on the crystal structure refinement from 3D electron diffraction data, the structural formula of Ca-rich vyacheslavite studied is U0.895Ca0.105 PO4(OH)0.790(H2O)0.210. In general, such compositional variability involving Ca2+ can be expressed as U1–x CaxPO4(OH)1–2x(H2O)2x. Based on detailed electron-probe microanalysis, regions extremely enriched in Y and Ln have been discovered, characterized by the contents up to 11 wt% of Y2O3 and ~4.5 wt% of Ln2O3. In addition to the above-mentioned substitution mechanism, substitution involving Y and Ln can be expressed as U4+ + OH– → REE3+ + H2O. Although the structure refinement has not provided direct evidence of H2O in the studied nano-fragments of vyacheslavite, the presence of H2O and its substitution at OH– sites is a reasonable and necessary charge-balancing mechanism. One H atom site was located during structure refinements; however, an additional H-site is only partially occupied and thus was not revealed from the refinement despite the high-quality data. Substitutional trends observed here suggest possible miscibility or structural relationship between vyacheslavite, rhabdophane, and ningyoite that may depend strongly on OH/H2O content, considering that all crystallize under similar paragenetic conditions.
ER -
STECIUK, Gwladys, Radek ŠKODA, Veronika DILLINGEROVÁ a Jakub PLÁŠIL. Chemical variability in vyacheslavite, U(PO4)(OH): Crystal-chemical implications for hydrous and hydroxylated U4+, Ca, and REE phosphates. \textit{American Mineralogist}. Mineralogical Society of America, 2022, roč.~107, č.~1, s.~131-137. ISSN~0003-004X. Dostupné z: https://dx.doi.org/10.2138/am-2021-7875.
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