Alkali sulfates with aphthitalite-like structures from fumaroles of the Tolbachik volcano, Kamchatka, Russia. I. metath Énardite, a natural high-temperature modification of Na₂SO₄

Autor(en)

Igor V Pekov, Nadezhda V. Shchipalkina, Natalia V Zubkova, Vladislav V. Gurzhiy, Atali A. Agakhanov, Dmitry I. Belakovskiy, Nikita V. Chukanov, Inna S. Lykova, Marina F. Vigasina, Natalya Koshlyakova, Evgeny G. Sidorov, Gerald Giester

Abstrakt

A new mineral, metathénardite, ideally Na

₂SO

₄, the high-temperature hexagonal dimorph of thénardite, a natural analogue of the synthetic phase Na

₂SO

₄(I), was found in the sublimates of active fumaroles at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure eruption, Tolbachik volcano, Kamchatka, Russia. The holotype originates from the Glavnaya Tenoritovaya fumarole in which metathénardite is associated with hematite, tenorite, fluorophlogopite, sanidine, anhydrite, krasheninnikovite, vanthoffite, glauberite, johillerite, and lammerite. The cotypes 1 and 2 are from the Arsenarnaya (with hematite, tenorite, fluorophlogopite, sanidine, euchlorine, wulffite, anhydrite, fluoborite, johillerite, nickenichite, calciojohillerite, badalovite, tilasite, cassiterite, and pseudobrookite) and the Yadovitaya (with tenorite, euchlorine, fedotovite, dolerophanite, langbeinite, krasheninnikovite, anhydrite, and hematite) fumaroles, respectively. All specimens with metathénardite were collected from areas with temperatures of 350-400 °C. Metathénardite forms hexagonal tabular, lamellar, or dipyramidal crystals (forms: {001}, {100}, {102}, and {201}) up to 3 mm combined in crusts up to several hundred cm

²in area. The mineral is transparent to semitransparent, colorless, white, light-blue, greenish, yellowish, grayish or brownish, with vitreous luster. D

_meas.=2.72(1), D

_calc.=2.717 g/cm

³. Metathénardite is optically uniaxial (-), ω=1.489(2), ϵ=1.486(2). The empirical formulae are (Na

_1.92K

_0.05Ca

_0.02Zn

_0.01)[S

_0.99O

₄] (holotype), (Na

_1.54K

_0.22Ca

_0.09Cu

_0.01Mg

_0.01)[S

_1.00O

₄] (cotype 1), and Na

_1.65K

_0.11Ca

_0.05Cu

_0.04Mg

_0.01)[S

_1.01O

₄] (cotype 2). Admixed K and bivalent cations probably stabilize the hexagonal aphthitalite-like structure of metathénardite at room temperature. The crystal structure was solved using single crystals of all three samples, R

₁= 0.0852, 0.0452, and 0.0449 for holotype and cotypes 1 and 2, respectively. The space group is P6

₃/mmc, and the unit-cell parameters of the holotype are a = 5.3467(9), c = 7.0876(16) Å, V = 157.47(6) Å

³, and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d,Å (I)(hkl)] are: 4.667(27)(100), 3.904(89)(101), 3.565(33)(002), 2.824(94)(102), 2.686(100)(110), and 1.939(35)(202). Metathénardite and thénardite clearly differ from one another in X-ray diffraction data and infrared and Raman spectra.

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Saint Petersburg State University, Russian Academy of Sciences, Canadian Museum of Nature, Lomonosov Moscow State University (MSU)

Journal

The Canadian Mineralogist

Band

57

Seiten

885-901

Anzahl der Seiten

17

ISSN

0008-4476

DOI

https://doi.org/10.3749/canmin.1900050

Publikationsdatum

11-2019

Peer-reviewed

Ja

ÖFOS 2012

105116 Mineralogie, 105113 Kristallographie

Schlagwörter

ASJC Scopus Sachgebiete

Geochemistry and Petrology

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/e5edd3b4-44d9-453f-af7b-30e774244b94