Vasiliy O. Yapaskurt

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. I. Yurmarinite, Na7(Fe3+,Mg,Cu)4(AsO4)6

Abstract A new mineral, yurmarinite, Na7(Fe3+,Mg,Cu)4(AsO4)6, occurs in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with hatertite, bradaczekite, johillerite, hematite, tenorite, tilasite and aphthitalite. Yurmarinite occurs as well-shaped, equant crystals up to 0.3 mm in size, their clusters up to 0.5 mm and thin, interrupted crystal crusts up to 3 mm × 3 mm on volcanic scoria. Crystal forms are {101}, {011}, {100}, {110} and {001}. Yurmarinite is transparent, pale green or pale yellowish green to colourless. The lustre is vitreous and the mineral is brittle. The Mohs hardness is ~4½. One direction of imperfect cleavage was observed, the fracture is uneven. D(calc.) is 4.00 g cm-3. Yurmarinite is optically uniaxial (-), ω = 1.748(5), ε = 1.720(3). The Raman spectrum is given. The chemical composition (wt.%, electron microprobe data) is Na2O 16.85, K2O 0.97, CaO 1.28, MgO 2.33, MnO 0.05, CuO 3.17, ZnO 0.97, Al2 O3 0.99, Fe2O3 16.44, TiO2 0.06, P2O5 0.12, V2O5 0.08, As2O5 56.68, total 99.89. The empirical formula, calculated on the basis of 24 O atoms per formula unit, is (Na6.55Ca0.28K0.22)∑7.05(Fe3+2.48Mg0.70Cu0.48Al0.23Zn0.14 Ti0.01Mn0.01)∑4.05(As5.94P0.02V0.01)∑5.97O24. Yurmarinite is rhombohedral, R3̅ c, a = 13.7444(2), c = 18.3077(3) Å, V = 2995.13(8) Å3, Z = 6. The strongest reflections in the X-ray powder pattern [d,Å (I)(hkl)] are: 7.28(45)(012); 4.375(33)(211); 3.440(35)(220); 3.217(36)(131,214); 2.999(30)(223); 2.841(100)(125); 2.598(43)(410). The crystal structure was solved from single-crystal X-ray diffraction data to R = 0.0230. The structure is based on a 3D heteropolyhedral framework formed by M4O18 clusters (M = Fe3+ > Mg,Cu) linked with AsO4 tetrahedra. Sodium atoms occupy two octahedrally coordinated sites in the voids of the framework. In terms of structure, yurmarinite is unique among minerals but isotypic with several synthetic compounds with the general formula (Na7-x⃞x)(M3+3+xM2+1-x)(T5+O4)2 in which T = As or P, M3+ = Fe or Al, M2+ = Fe and 0 ≤ x ≤ 1. The mineral is named in honour of the Russian mineralogist, petrologist and specialist in studies of ore deposits, Professor Yuriy B. Marin (b. 1939). The paper also contains a description of the Arsenathaya fumarole and an overview of arsenate minerals formed in volcanic exhalations.

Cretaceous volcanic belts and the evolution of the Black Sea Basin

Deposits in southwestern Crimea that contain Late Albian, Middle Senomanian, and Middle Campanian volcanic material are described and dated. Supposedly volcanic edifices are identified in the Black Sea (the Shatsky Swell) based on seismic data. The Albian, Senomanian, and Campanian volcanic belts are reconstructed for the entire Black Sea Region. The suggestion is made that the Black Sea Basin formed as a back-arc basin that started from rifting in the Albian and finished with spreading of the oceanic crust in the Senomanian-Early Santonian.

Metamorphic evolution of the archean eclogite-like rocks of the Shirokaya and Uzkaya Salma area (Kola Peninsula): Geochemical features of zircon, composition of inclusions, and age

Zircon from the eclogite-like rocks of the Shirokaya and Uzkaya Salma area (Kola Peninsula) was studied using a complex of mineralogical and geochemical methods (CL, BSE, microprobe, and REE distribution). Different zones distinguished within zircon crystals were dated on a SHRIMP-II mass spectrometer. Mineral and chemical compositions of inclusions in the zircons were analyzed. Based on these studies, the following stages of the formation and transformation of the rocks were determined: (1) formation of basic protolith of the eclogite-like rocks of the Shirokaya and Uzkaya Salma area 2.94–2.93 Ga ago; (2) the granulite-facies metamorphism of the eclogite-like rocks of the Shirokaya Salma 2.72 Ga ago; (3) the onset of decompressional cooling with formation of Cpx-Pl symplectites at 2.70 Ga ago; and (4) final metamorphic reworking together with surrounding TTG under the amphibolite-facies conditions at 1.89 Ga ago. The studied rocks and minerals revealed no isotope-geochemical or geochronological signs of eclogite metamorphism. Geochemistry of the primary magmatic zircons showed that the protolith of eclogite-like rocks was gabbro rather than MOR basalts. The formation of garnet in the rocks of the Uzkaya and Shirokaya Salma area is dated at 2.70 and 1.89 Ga ago, which is consistent with petrological observations of later formation of garnet relative to omphacite. Obtained data led us to prefer a magmatogenic model, which suggests that omphacite in the rocks of the Shirokaya and Uzkaya Salma was presumably formed during crystallization from basic melt, rather than during eclogite-facies metamorphism.

Starovaite, KCu5O(VO4)3, a new mineral from fumarole sublimates of the Tolbachik volcano, Kamchatka, Russia

The new mineral species starovaite, ideally KCu 5 O(VO 4 )3, has been found in the sublimates of the Yadovitaya fumarole at the Second scoria cone of the Northern Breach of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. The mineral is associated with lammerite, hematite, palmierite, tenorite, piypite, rutile, orthoclase, lyonsite, pseudolyonsite, lammerite-β, langbeinite, calciolangbeinite, and cupromolybdite. Starovaite occurs as prismatic crystals up to 3 × 6 × 20 μm or divergent long-prismatic crystals up to 1 × 3 × 70 μm. The crystals are combined in sprays, sheaf-like aggregates or crusts up to 0.3 × 0.5 mm overgrowing lammerite. Starovaite is golden brown to reddish brown with a semi-metallic luster. The mineral is brittle, VHN is 182 (range 165–195) kg mm −2 . Cleavage and parting were not observed, fracture is uneven. D (calc.) = 4.54 g cm −3 . In reflected light, starovaite is grey with a brownish hue. Bireflectance is weak, internal reflections are distinct red-brown, anisotropy is weak. The reflectance values [ R 1 −R 2 , % (λ, nm)] are: 14.2–12.45 (470), 13.2–11.6 (546), 13.0–11.4 (589), 12.6–11.35 (650). The chemical composition (wt%, electron microprobe data) is: K 2 O 4.90, CaO 0.04, PbO 1.29, CuO 48.20, ZnO 5.59, Al 2 O 3 0.08, Fe 2 O 3 0.10, P 2 O 5 0.05, As 2 O 5 4.49, V 2 O 5 31.89, SO 3 0.19, MoO 3 2.34, total 99.16. The empirical formula calculated on the basis of 13 O apfu is: (K 0.76 Pb 0.04 Ca 0.01 ) Σ0.81 (Cu 4.45 Zn 0.51 Al 0.01 Fe 0.01 ) Σ4.98 (V 2.58 As 0.29 Mo 0.12 S 0.02 P 0.01 ) Σ3.02 O 13 . Starovaite is triclinic, P –1, a = 6.08(4), b = 8.26(5), c = 10.71(6) A, α = 97.8(1), β = 92.4(1), γ = 90.4(1)°, V = 532(2) A 3 , and Z= 2. The strongest reflections of the X-ray powder diffraction pattern [ d , A ( I , %) (hkl)] are: 10.62 (32) (001); 8.18 (46) (010); 3.047 (41) (022, 200,12-2); 2.745 (47) (2-1-1, 03-1); 2.526 (100) (031, 2-12, 2-1-2, 023, 1-31,13-1); 2.322 (98) (03-3, 21-3, 221, 22-2); 1.867 (23) (302); 1.410 (23) (24-5, 053,41-3, 03-7). Starovaite is a natural analogue of synthetic KCu 5 O(VO 4 )3. The mineral is named in honour of the Russian crystallographer and crystal chemist Galina L. Starova (b. 1946) for her contributions to the crystal chemistry of minerals from the Tolbachik fumaroles.

Yaroshevskite, Cu9O2(VO4)4Cl2, a new mineral from the Tolbachik volcano, Kamchatka, Russia

Abstract A new mineral, yaroshevskite, ideally Cu9O2(VO4)4Cl2, occurs in sublimates collected from the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with euchlorine, fedotovite, hematite, tenorite, lyonsite, melanothallite, atlasovite, kamchatkite and secondary avdoninite, belloite and chalcanthite. Yaroshevskite forms isolated prismatic crystals, up to 0.1 × 0.15 × 0.3 mm in size, on the surface of euchlorine crusts. The mineral is opaque and black, with a reddish black streak and lustre between metallic and adamantine. Yaroshevskite is brittle, no cleavage was observed and the fracture is uneven. The Mohs hardness is ~3½ (corresponding to a mean VHN micro-indentation hardness of 172 kg mm-2) and the calculated density is 4.26 g cm-3. In reflected light, yaroshevskite is grey with a weak bluish hue. Pleochroism, internal reflections and bireflectance were not observed. Anisotropy is very weak. The composition (wt.%) determined by electron microprobe is: CuO 61.82, ZnO 0.53, Fe2O3 0.04, V2O5 31.07, As2O5 0.32, MoO3 1.56, Cl 6.23, O=Cl2 -1.41; total 100.16. The empirical formula, calculated on the basis of 20 (O + Cl) anions is (Cu8.80Zn0.07Fe0.01)Σ8.88 (V3.87Mo0.12As0.03)Σ4.02O18.01Cl1.99. Yaroshevskite is triclinic, space group P1̅, a = 6.4344(11), b = 8.3232(13), c = 9.1726(16) Å , α = 105.338(14), β = 96.113(14), γ = 107.642(1)º, V = 442.05(13) Å3 and Z = 1. The nine strongest reflections in the X-ray powder pattern [dobs in Å (I)(hkl)] are as follows: 8.65(100)(001); 6.84(83)(01̅1); 6.01(75)(100); 5.52(60)(1̅01); 4.965(55)(011); 4.198(67)(11̅1̅); 4.055(65)(110); 3.120(55)(021); 2.896(60)(211̅,003,2̅20). The crystal structure was solved by direct methods from single-crystal X-ray diffraction data and refined to R = 0.0737. The yaroshevskite structure is unique. It is based on corrugated layers made up of chains of edge-sharing flat squares with central Cu2+ cations [Cu(1), Cu(4) and Cu(5)]; neighbouring chains are connected via groups consisting of three Cu2+-centred squares [two Cu(3) and Cu(6)]. Neighbouring layers are connected via pairs of Cu(2)O4Cl five-coordinate polyhedra and isolated VO4 tetrahedra. The structure of yaroshevskite can also be considered in terms of oxygen-centred tetrahedra: O(7)Cu4 tetrahedra are connected via common Cu(4) and Cu(5) vertices to form pyroxene-like chains [O2Cu6]∞. In this context, the structural formula can be written Cu3[O2Cu6][VO4]4Cl2. The mineral name honours the Russian geochemist Alexei A. Yaroshevsky (b. 1934) of Moscow State University.

Koksharovite, CaMg2Fe3+ 4(VO4)6, and grigorievite, Cu3Fe3+ 2Al2(VO4)6, two new howardevansite-group minerals from volcanic exhalations

Two new howardevansite-group minerals were discovered in the exhalations of fumaroles related to two volcanoes in Kamchatka, Russia. Koksharovite, CaMg2Fe 3þ 4(VO4)6, is found at the Bezymyannyi volcano in association with bannermanite. Grigorievite, Cu3Fe 3þ 2Al2(VO4)6, associated with bannermanite, ziesite, hematite, etc., was found at the Second scoria cone of the NorthernBreakthroughoftheGreatTolbachikFissureEruption,Tolbachikvolcano.Koksharoviteoccursasequanttoprismaticcrystals upto30 � 70mm.Itistranslucent,yellowish-browntoreddish-brownwithanadamantinelustre.Grigorieviteformsprismatic totabular crystals up to 40 � 100 mm. It is opaque, black with a semi-metallic lustre. Both minerals are brittle. The VHN hardness is 368 and 489 kg mm � 2 , the calculated density (Dcalc) 3.39 and 3.67 g cm � 3 for koksharovite and grigorievite, respectively. In reflected light, koksharovite is light grey, grigorievite is grey; both minerals are weakly anisotropic. Reflectance values (koksharovite//grigorievite: Rmax-Rmin ,%( l, nm)) are: 15.3-14.4//16.8-16.4 (470), 14.1-13.2//15.9-15.5 (546), 13.8-13.0//15.3-14.9 (589), 13.4-12.7//14.8-14.1 (650). Chemical data (wt%, electron-microprobe analysis; first value is for koksharovite, second for grigorievite) are: Na2O 0.76, 0.00; K2O 0.05, 0.00; MgO 9.43,2.78; CaO 3.57, 0.95; MnO 0.46,0.04;CuO 0.00,17.70; NiO 0.11, 0.00;ZnO 0.00,0.14; Al2O3 3.04,11.76; Fe2O3 23.88, 10.10; TiO2 2.42, 1.47; SiO2 0.20, 0.00; P2O5 0.98, 0.13; V2O5 53.86, 54.97; total 98.76, 100.04. The empirical formulae, based on 24 O atoms per formula unit, are: Na0.24K0.01Ca0.63Mg2.30Mn0.06Ni0.01Al0.59Fe 3þ 2.94Ti0.30Si0.03P0.14V5.83O24 (koksharovite); Ca0.17Mg0.69Mn0.01Cu2.23Zn0.02Al2.31Fe 3þ 1.27Ti0.18P0.02V6.05O24(grigorievite).Bothmineralsaretriclinic,spacegroupP-1,Z ¼1.Unit-

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. IV. Shchurovskyite, K2CaCu6O2(AsO4)4 and dmisokolovite, K3Cu5AlO2(AsO4)4

Abstract Two new minerals shchurovskyite, ideally K2CaCu6O2(AsO4)4, and dmisokolovite, ideally K3Cu5AlO2(AsO4)4, are found in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. They are associated with one another and with johillerite, bradaczekite, tilasite, melanarsite, tenorite, hematite, aphthitalite, langbeinite, orthoclase, etc. Shchurovskyite occurs as coarse tabular or prismatic crystals up to 0.15 mm in size or anhedral grains forming parallel aggregates and crusts up to 1.5 cm × 2 cm across. Dmisokolovite forms tabular, prismatic or dipyramidal crystals up to 0.2 mm in size, commonly combined in clusters or crusts up to 0.7 cm × 1.5 cm across. Both minerals are transparent with a vitreous lustre. They are brittle, with Mohs’ hardness ≈ 3. Shchurovskyite is olive-green or olive drab. Dmisokolovite is bright emerald-green to light green. Dcalc = 4.28 (shchurovskyite) and 4.26 (dmisokolovite) g cm−3. Both are optically biaxial; shchurovskyite: (+), α = 1.795(5), β = 1.800(5), γ = 1.810(6), 2Vmeas = 70(15)°; dmisokolovite: (−), α = 1.758(7), β = 1.782(7), γ = 1.805(8), 2Vmeas = 85(5)°. The Raman spectra are given. Chemical data (wt.%, electron-microprobe; first value is for shchurovskyite, second for dmisokolovite):Na2O 0.00, 0.83;K2O 8.85, 10.71; Rb2O 0.11, 0.00;MgO 0.00, 0.35; CaO 4.94, 0.21; CuO 43.19, 38.67; ZnO 0.42, 0.20; Al2O3 0.04, 4.68; Fe2O3 0.00, 0.36; P2O5 0.59, 0.78; V2O5 0.01, 0.04; As2O5 40.72, 43.01; SO3 0.35, 0.00; total 99.22, 99.84. The empirical formulae, based on 18 O a.p.f.u., are shchurovskyite: K2.05Rb0.01Ca0.96Cu5.92Zn0.06Al0.01P0.09S0.05As3.86O18; dmisokolovite: Na0.28K2.36Mg0.09C a0.04Cu5.04Zn0.04 Al0.95Fe0.053+P0.11As3.88O18. The strongest reflections of X-ray powder patterns [d,Å(I)(hkl)] are shchurovskyite: 8.61(100)(200, 001), 5.400(32)(110), 2.974(32)(3̅12, 510), 2.842(47)(003, 020), 2.757(63) (6̅01, 511), 2.373(36)(512, 420) and 2.297(31)( 4̅21, 2̅22, 313); dmisokolovite: 8.34(95)(002), 5.433(84)(110), 2.921(66)(510, 3̅14), 2.853(58)(511, 020) and 2.733(100)(006, 512, 6̅02). Shchurovskyite is monoclinic, C2, a = 17.2856(9), b = 5.6705(4), c = 8.5734(6) Å, β = 92.953(6)°, V = 839.24(9) Å3 and Z = 2. Dmisokolovite is monoclinic, C2/c, a = 17.0848(12), b = 5.7188(4), c = 16.5332(12) Å, β = 91.716(6)°, V = 1614.7(2) Å3 and Z = 4. Their crystal structures [single-crystal X-ray diffraction data, R = 0.0746 (shchurovskyite) and 0.1345 (dmisokolovite: model)] are closely related in the topology of the main building units. They are based on a quasi-framework consisting of AsO4 tetrahedra and polyhedra centred by Cu in shchurovskyite or by Cu and Al in dmisokolovite. K and Ca are located in channels of the quasi-framework. The minerals are named in honour of outstanding Russian geologists and mineralogists Grigory Efimovich Shchurovsky (1803−1884) and Dmitry Ivanovich Sokolov (1788-1852).

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. II. Ericlaxmanite and kozyrevskite, two natural modifications of Cu4O(AsO4)2

Abstract Two new minerals, ericlaxmanite and kozyrevskite, dimorphs of Cu4O(AsO4)2, were found in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. They are associated with each other and with urusovite, lammerite, lammerite-b, popovite, alarsite, tenorite, hematite, aphthitalite, langbeinite, As-bearing orthoclase, etc. Ericlaxmanite occurs as tabular, lamellar, equant or short prismatic crystals up to 0.1 mm in size, their clusters and pseudomorphs after urusovite crystal crusts up to 1.5 cm × 2 cm in area. Kozyrevskite occurs as prismatic crystals up to 0.3 mm long in clusters and as individual crystals. Both minerals are transparent with a vitreous lustre. They are brittle, with Mohs’ hardness ~3½. Ericlaxmanite is green to dark green. Kozyrevskite is bright grass green to light yellowish green; Dcalc is 5.036 (ericlaxmanite) and 4.934 (kozyrevskite) g cm-3. Both minerals are optically biaxial (–); ericlaxmanite: α = 1.870(10), β = 1.900(10), γ = 1.915(10), 2Vmeas = 60(15)°; kozyrevskite: α = 1.885(8), β = 1.895(8), γ = 1.900(8), 2Vmeas. = 75(10)°. The Raman spectra are given. Chemical data (wt.%, electron microprobe; the first value is for ericlaxmanite, the second for kozyrevskite): CuO 57.55, 58.06; ZnO 0.90, 1.04; Fe2O3 0.26, 0.12; SiO2 n.d., 0.12; P2O5 0.23, 1.23; V2O5 0.14, 0.37; As2O5 40.57, 38.78; SO3 0.17, 0.43; total 99.82, 100.15. The empirical formulae, based on 9 O a.p.f.u., are: ericlaxmanite: (Cu3.97Zn0.06Fe0.02)∑4.05(As1.94P0.02V0.01S0.01)∑1.98O9 and kozyrevskite: (Cu3.95Zn0.07Fe0.01)∑4.03(As1.83P0.09S0.03V0.02Si0.01)∑1.98O9. Ericlaxmanite is triclinic, P1̄ , a = 6.4271(4), b = 7.6585(4), c = 8.2249(3) Å , α = 98.396(4), β = 112.420(5), γ = 98.397(5)°, V = 361.11(3) Å3 and Z = 2. Kozyrevskite is orthorhombic, Pnma, a = 8.2581(4), b = 6.4026(4), c = 13.8047(12) Å , V = 729.90(9) Å3 and Z = 4. The strongest reflections in the X-ray powder patterns [d Å (I)(hkl)] are: ericlaxmanite: 3.868(46)(101), 3.685(100)(020), 3.063(71)(012), 2.957(58)(02̄ 2), 2.777(98)(2̄ 12, 2̄1 1), 2.698(46)(2̄1̄2) and 2.201(51)(013, 031); kozyrevskite: 3.455(100)(004), 3.194(72)(020, 104), 2.910(69)(022), 2.732(82)(122), 2.712(87)(301) and 2.509(92)(123). Their crystal structures, solved from single-crystal X-ray diffraction data [R = 0.0358 (ericlaxmanite) and 0.1049 (kozyrevskite)], are quite different. The ericlaxmanite structure is based on an interrupted framework built by edge- and corner-sharing Cu-centred, distorted tetragonal pyramids, trigonal bipyramids and octahedra. The kozyrevskite structure is based on complicated ribbons of Cu-centred distorted tetragonal pyramids and trigonal bipyramids. Ericlaxmanite is named in honour of the Russian mineralogist, geologist, geographer, biologist and chemist Eric Laxman (1737-1796). Kozyrevskite is named in honour of the Russian geographer, traveller and military man Ivan Petrovich Kozyrevskiy (1680-1734), one of the first researchers of Kamchatka.

Calciolangbeinite, K2Ca2(SO4)3, a new mineral from the Tolbachik volcano, Kamchatka, Russia

Abstract The new mineral calciolangbeinite, ideally K2Ca2(SO4)3, is the Ca-dominant analogue of langbeinite. It occurs in sublimates at the Yadovitaya fumarole on the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure eruption, Tolbachik volcano, Kamchatka, Russia. The mineral is associated with langbeinite, piypite, hematite, rutile, pseudobrookite, orthoclase, lyonsite, lammerite, cyanochroite and chlorothionite. Calciolangbeinite occurs as tetrahedral to pseudooctahedral crystals, which are bounded by {111} and {111̅}, and as anhedral grains up to 1 mm in size, aggregated into clusters up to 2 mm across, and forming crusts covering areas of up to 1.5 6 1.5 cm on the surface of volcanic scoria. Late-stage calciolangbeinite occurs in complex epitaxial intergrowths with langbeinite. Calciolangbeinite is transparent and colourless with white streak and vitreous lustre. Its Mohs’ hardness is 3-3½. It is brittle, has a conchoidal fracture and no obvious cleavage. The measured and calculated densities are D meas = 2.68(2) and D calc = 2.74 g cm-3, respectively. Calciolangbeinite is optically isotropic with n = 1.527(2). The chemical composition of the holotype specimen is Na2O 0.38, K2O 21.85, MgO 6.52, CaO 16.00, MnO 0.27, FeO 0.08, Al2O3 0.09, SO3 55.14, total 100.63 wt.%. The empirical formula, calculated on the basis of twelve oxygen atoms per formula unit, is K2.01(Ca1.24Mg0.70Na0.05Mn0.02Fe0.01Al0.01)S 2.03S3.00O12. Calciolangbeinite is cubic, space group P213, a = 10.1887(4) Å, V = 1057.68(4) Å3 and Z = 4. The strongest reflections in the X-ray powder pattern [listed as (d,Å(I)(hkl)] are 5.84(8)(111); 4.54(9)(120); 4.15(27)(211); 3.218 (100) (310, 130); 2.838 (8) (230, 320), 2.736 (37) (231, 321), 2.006 (11) (431, 341) , 1.658(8)(611,532,352). The crystal structure was refined from single-crystal X-ray diffraction data to R = 0.0447. The structure is based on the langbeinite-type three-dimensional complex framework, which is made up of (Ca,Mg)O6 octahedra (Ca and Mg are disordered) and SO4 tetrahedra. Potassium atoms occupy two sites in voids in the framework; K(1) cations are located in ninefold polyhedra whereas K(2) cations are sited in significantly distorted octahedra. Calciolangbeinite and langbeinite are isostructural and form a solid-solution series.

Tourmaline in the Vetka Porphyry Copper-Molybdenum Deposit of the Chukchi Peninsula of Russia

Three generations of tourmaline have been identified in propylite in the Vetka porphyry copper-molybdenum deposit of the Chukchi Peninsula of Russia. Tourmaline-I is characterized by its Fetot/(Fetot + Mg) value, which ranges from 0.33 to 0.49. Tourmaline-II, which crystallizes at a lower temperature, overgrowing tourmaline-I or occurring as isolated crystals, is distinguished by a higher Fetot/(Fetot + Mg), which varies from 0.46 to 0.72. The Fetot/(Fetot + Mg) ratio in tourmaline-III, which overgrows tourmaline-II is lower (0.35–0.49), and is identical to that of the first tourmaline generation. This is probably caused by the beginning of sulfide deposition. Tourmalines in the deposit characterized by complex isomorphic substitutions can be attributed to the intermediate members of the dravite—“hydroxy-uvite”-“oxy-uvite” and schorl-“hydroxy-feruvite”-“oxy-feruvite” series. Tourmaline starts to crystallize at temperatures above 340°C. The fluid responsible for the tourmaline deposition was magmatic, with a significant admixture of meteoric water (δ18OH2O = −0.85 to −0.75‰). The high Fe3+/Fetot ratio (0.50) indicates high oxygen activity when the tourmaline precipitated. It has been established that the isomorphic substitution Fetot → Al is typomorphic of tourmalines from porphyry copper deposits worldwide.