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@article{1317533,
author = {Škoda, Radek and Plášil, Jakub and Jonsson, Erik and Čopjaková, Renata and Jörgen, Langhof and Vašinová Galiová, Michaela},
article_number = {4},
doi = {http://dx.doi.org/10.1180/minmag.2015.079.4.07},
keywords = {thalénite-(Y); fluorthalénite-(Y); fluorine; Y+REE; electron microprobe analysis; single crystal X-ray diffraction; LA-ICP-MS; tetrad effect; Österby; Bergslagen; Sweden},
language = {eng},
issn = {0026-461X},
journal = {Mineralogical Magazine},
title = {Redefinition of thalénite-(Y) and discreditation of fluorthalénite-(Y): A re-investigation of type material from the Österby pegmatite, Dalarna, Sweden, and from additional localities},
volume = {79},
year = {2015}
}
TY - JOUR
ID - 1317533
AU - Škoda, Radek - Plášil, Jakub - Jonsson, Erik - Čopjaková, Renata - Jörgen, Langhof - Vašinová Galiová, Michaela
PY - 2015
TI - Redefinition of thalénite-(Y) and discreditation of fluorthalénite-(Y): A re-investigation of type material from the Österby pegmatite, Dalarna, Sweden, and from additional localities
JF - Mineralogical Magazine
VL - 79
IS - 4
SP - 965-983
EP - 965-983
PB - Mineralogical Society
SN - 0026461X
KW - thalénite-(Y)
KW - fluorthalénite-(Y)
KW - fluorine
KW - Y+REE
KW - electron microprobe analysis
KW - single crystal X-ray diffraction
KW - LA-ICP-MS
KW - tetrad effect
KW - Österby
KW - Bergslagen
KW - Sweden
N2 - Using type material from the Österby pegmatite in Dalarna, Sweden, the chemical composition and structural parameters of thalénite-(Y) [ideally Y3Si3O10(OH)] were examined by wavelength dispersive spectroscopy electron microprobe (WDS EMP) analysis and single-crystal X-ray diffraction. High contrast back-scatter electron images of the Österby material show at least two generations of thalénite-(Y). The formula of the primary thalénite-(Y) normalized to 11 anions is (Y2.58Dy0.11Yb0.09Gd0.06Er0.06Ho0.02Sm0.02Tb0.02Lu0.02Nd0.01Tm0.01sum3.00Si3.01O10F0.97OH0.03. The secondary thalénite-(Y), replacing the primary material, is weakly enhanced in Y and depleted in the lightest and the heaviest rare-earth elements, yielding the formula (Y2.63Dy0.12Yb0.06Gd0.06Er0.05Ho0.02Sm0.02Tb0.02Tm0.01Nd0.01Lu0.01)sum3.00Si3.01O10F0.98OH0.02. Structural data for thalénite-(Y) from Österby clearly indicate the monoclinic space group P21/n, with a = 7.3464(4), b = 11.1726(5), c = 10.4180(5) Angstoms, beta = 97.318(4)°, V = 848.13(7) cubic Angstoms, Z = 4, which is consistent with previous investigations. The structure was refined from single-crystal X-ray diffraction data to R1 = 0.0371 for 1503 unique observed reflections, and the final chemical composition obtained from the refinement, (Y2.64Dy0.36)sum3.00F0.987[Si3O10], Z = 4, is in good agreement with the empirical formula resulting from electron microprobe (EMP) analysis. Both techniques reveal a strong dominance of F over OH, which means that the type material actually corresponds to the fluorine analogue. Moreover, new EMP analyses of samples of thalénite-(Y) from an additional seven localities (Askagen and Reunavare in Sweden; White Cloud and Snow Flake in Colorado, USA; the Guy Hazel claim in Arizona, USA; Suishoyama and Souri in Japan) clearly show the prevalence of F over OH as well. Based on these observations, the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association has recommended a redefinition of the chemical composition of thalénite-(Y) to represent the F-dominant species with the ideal formula Y3Si3O10F, as it has historical priority. Consequently, the later described fluorthalénite-(Y) has to be discredited.
ER -
ŠKODA, Radek, Jakub PLÁŠIL, Erik JONSSON, Renata ČOPJAKOVÁ, Langhof JÖRGEN and Michaela VAŠINOVÁ GALIOVÁ. Redefinition of thalénite-(Y) and discreditation of fluorthalénite-(Y): A re-investigation of type material from the Österby pegmatite, Dalarna, Sweden, and from additional localities. \textit{Mineralogical Magazine}. Mineralogical Society, 2015, vol.~79, No~4, p.~965-983. ISSN~0026-461X. Available from: https://dx.doi.org/10.1180/minmag.2015.079.4.07.
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