Unique thallium mineralization in the fumaroles of the Tolbachik volcano, Kamchatka Peninsula, Russia. II. Karpovite, Tl₂VO(SO₄)₂(H₂O)

Abstract

Karpovite, ideally Tl2VO(SO4)2(H2O), was found in a fumarole of the 1st cinder cone of the North Breach of the Great Fissure Tolbachik volcano eruption (1975–1976), Kamchatka Peninsula, Russia. Karpovite occurs as bundles of white, needle-like crystals associated with shcherbinaite, pauflerite, bobjonesite, markhininite, evdokimovite and microcrystalline Mg, Al, Fe and Na sulfates. Karpovite is monoclinic, P21, a = 4.6524(4), b = 11.0757(9), c = 9.3876(7) Å , β = 98.353(2)º, V = 478.60(7) Å3, Z = 2 (from single-crystal diffraction data). The eight strongest lines of the X-ray powder diffraction pattern are (I/d/hkl): 64/4.289/012, 81/4.253/110, 38/3.683/111, 47/3.557/022, 100/3.438/1̄21, 52/2.982/013, 59/2.945/112, 54/2.354/132. The chemical composition determined by the electron microprobe analysis is (wt.%) Tl2O 61.43, VO2 11.53, SO3 23.55, H2O 2.61, total 99.12. The empirical formula (calculated on the basis of 10 O a.p.f.u.) is Tl2.00V0.96S2.03O9(H2O). The simplified formula of karpovite is Tl2VO(SO4)2(H2O), which requires Tl2O 61.93, VO2 12.09, SO3 23.34, H2O 2.62 total 100.00 wt.%. The crystal structure was solved by direct methods and refined to R1 = 0.026 for 4196 independent observed reflections. The structure contains two symmetrically independent Tl+ sites, one V4+ site and two S6+ sites. VO5H2O octahedra and SO4 tetrahedra link together by sharing corners to form kröhnkite-type stripes parallel to the a axis with their planes oriented parallel to (021) and (021̄ ). Tl+ cations are located between the chains, linked into a three-dimensional structure. The new mineral is named in honour of Professor Gennadii Alexandrovich Karpov (b. 1938), volcanologist at the Institute of Volcanology, Russian Academy of Sciences, Petropavlovsk-Kamchatskii, Kamchatka Peninsula, Russia.

Saranchinaite, Na2Cu(SO4)2, a new exhalative mineral from Tolbachik volcano, Kamchatka, Russia, and a product of the reversible dehydration of kröhnkite, Na2Cu(SO4)2(H2O)2

“…However, it should be noted that transformation and decomposition of kröhnkite revealed in the course of our HTXRD study is different as reported below. Kröhnkite-type compounds with various octahedrally coordinated cations and T 6+ O 4 ( T 6+ = S, Cr and Se) groups are abundant in both minerals and synthetic compounds (Driscoll et al ., 2016; Marinova et al ., 2015; Siidra et al ., 2014; Barpanda et al ., 2014; Saha et al ., 2011; Yang et al ., 2011; Stoilova et al ., 2009 a , b ; Wierzbicka-Wieczorek et al ., 2008; Behera and Rao, 2006; Kolitsch and Fleck, 2005, 2006; Fleck and Kolitsch, 2003; Wildner and Stoilova, 2003; Pasha et al ., 2003; Fleck et al ., 2002 a , b ).…”

Unique thallium mineralization in the fumaroles of Tolbachik volcano, Kamchatka Peninsula, Russia. III. Evdokimovite, Tl4(VO)3(SO4)5(H2O)5

“…In each octahedron, there is one short VO vanadyl bond (1.60, 1.61 and 1.56 Å for V1, V2, and V3, respectively) opposite to one long VÀH 2 O bond (2.31, 2.19 and 2.21 Å for V1, V2 and V3, respectively). The coordination of V 4+ in evdokimovite is similar to that in the structure of karpovite (Siidra et al, 2014b) and is typical for vanadium oxysalts with V 4+ in [1+4+1] coordination (Schindler et al, 2000).…”

“…The crystal structure of evdokimovite is unique among known oxysalt minerals and synthetic compounds (Krivovichev, 2009) Figure 7 provides graph representations and indicates close structural relationships of the heteropolyhedral units observed in markhininite (Siidra et al, 2014a), karpovite (Siidra et al, 2014b) and evdokimovite. The structure of evdokimovite is strongly controlled by the stereochemical activity of the so-called 'lone electron pairs' on the Tl + cations.…”

“…The modulated character of the [(VO) 2 (H 2 O) 3 SO 4 ) 3 ] 2À chains and the wave-like arrangement of the [(VO)(H 2 O) 2 (SO 4 ) 2 ] 2À chains is obviously influenced by the large Tl + cations with strongly asymmetric coordination environments. Table 8 provides information on ECC v (volume eccentricity) parameters (Makovicky and Balić-Ž unić, 1998) calculated with the computer program IVTON v.2 (Balić-Ž unić and Vickovic, 1996) for markhininite (Siidra et al, 2014a), karpovite (Siidra et al, 2014b) Table 8 shows that stereochemical activity of the so-called 'lone electron pairs' on the Tl + cations occurs in the structures with the presence of even moderate Lewis bases such as O atoms of terminal vanadyl ions and terminal O atoms of SO 4 groups, i.e. in karpovite and markhininite.…”

“…EVDOKIMOVITE is one of three new minerals described from the unusual Tl(I)-rich sulfate mineral assemblage of the Tolbachik volcano, Kamchatka Peninsula, Russia (Fedotov and Markhinin, 1983). During the investigation of markhininite (Siidra et al, 2014a) samples, on the basis of semi-quantitative scanning electron microscopy (SEM) energy dispersive spectroscopy analysis, two new species were found: evdokimovite and karpovite (Siidra et al, 2014b). Evdokimovite was named in honour of Professor Mikhail Dmitrievich Evdokimov (1940À2010).…”