Thomas Armbruster

Publications (5)5.45 Total impact

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  Available from: Krystian Prusik

  Article: Elbrusite-(Zr)--A new uranian garnet from the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia

  Irina O Galuskina, Evgeny V Galuskin, Thomas Armbruster, Biljana Lazic, Joachim Kusz, Piotr Dzierżanowski, Viktor M Gazeev, Nikolai N Pertsev, Krystian Prusik, E Zadov, Antoni Winiarski, Roman Wrzalik, Anatoly G Gurbanov
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  ABSTRACT: absTracT Elbrusite-(Zr) Ca 3 (U 6+ Zr)(Fe 3+ 2 Fe 2+)O 12 , a new uranian garnet (Ia3d, a ≈ 12.55 Å, V ≈ 1977 Å 3 , Z = 8), within the complex solid solution elbrusite-kimzeyite-toturite Ca 3 (U,Zr,Sn,Ti,Sb,Sc,Nb...) 2 (Fe,Al,Si,Ti) 3 O 12 was discovered in spurrite zones in skarn xenoliths of the Upper Chegem caldera. The empirical formula of holotype elbrusite-(Zr) with 25.14 wt% UO 3 is (Ca 3.040 Th 0.018 Y 0.001) Σ3.059 (U 6+ 0.658 Zr 1.040 Sn 0.230 Hf 0.009 Mg 0.004) Σ1.941 (Fe 3+ 1.575 Fe 2+ 0.559 Al 0.539 Ti 4+ 0.199 Si 0.099 Sn 0.025 V 5+ 0.004) Σ3 O 12 . Associated minerals are spurrite, rondorfite, wadalite, kimzeyite, perovskite, lakargiite, ellestadite-(OH), hillebrandite, afwillite, hydrocalumite, ettringite group minerals, and hydrogrossular. Elbrusite-(Zr) forms grains up to 10–15 µm in size with dominant {110} and minor {211} forms. It often occurs as zones and spots within Fe 3+ -dominant kimzeyite crystals up to 20–30 µm in size. The mineral is dark-brown to black with a brown streak. The density calculated on the basis of the empirical formula is 4.801 g/cm 3 The fol-lowing broad bands are observed in the Raman spectra of elbrusite-(Zr): 730, 478, 273, 222, and 135 cm –1 . Elbrusite-(Zr) is radioactive and nearly completely metamict. The calculated cumulative dose (α-decay events/mg) of the studied garnets varies from 2.50 × 10 14 [is equivalent to 0.04 displacement per atom (dpa)] for uranian kimzeyite (3.36 wt% UO 3), up to 2.05 × 10 15 (0.40 dpa) for elbrusite-(Zr) with 27.09 wt% UO 3 .
  American Mineralogist 01/2010; 95:1172-1181. · 2.17 Impact Factor
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  Available from: Irina O Galuskina

  Article: Lakargiite CaZrO3: A new mineral of the perovskite group from the North Caucasus, Kabardino-Balkaria, Russia

  Evgeny V Galuskin, Viktor M Gazeev, Thomas Armbruster, Aleksander E Zadov, Irina O Galuskina, Nikolai N Pertsev, Piotr Dzierżanowski, Milen Kadiyski, Anatoly G Gurbanov, Roman Wrzalik, Antoni Winiarski
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  ABSTRACT: Lakargiite CaZrO 3 —the zirconium analog of perovskite [Pbnm, a = 5.556(1), b = 5.715(1), c = 7.960(1) Å, V 252.7(1) Å 3 , Z = 4]—was discovered as an accessory mineral in high-temperature skarns in carbonate-silicate rocks occurring as xenoliths in ignimbrites of the Upper-Chegem (Verkh-niy Chegem) volcanic structure, the North Caucasus, Kabardino-Balkaria, Russia. Lakargiite forms pseudo-cubic crystals up to 30–35 μm in size and aggregates up to 200 μm. Lakargiite is associated with spurrite, larnite, calcio-olivine, calcite, cuspidine, rondorfite, reinhardbraunsite, wadalite, perovskite, and minerals of the ellestadite group. The new perovskite mineral belongs to the ternary solid solution CaZrO 3 -CaTiO 3 -CaSnO 3 with a maximum CaZrO 3 content of ca. 93%, maximum CaTiO 3 content of 22%, and maximum CaSnO 3 content of 20%. Significant impurities are Sc, Cr, Fe, Ce, La, Hf, Nb, U, and Th. Raman spectra of lakargiite are similar to those of the synthetic phase Ca(Zr,Ti)O 3 with strong bands at 352, 437, 446, 554, and 748 cm –1 . Lakargiite crystallized under sanidinite-facies conditions of contact metamorphism characterized by very high temperatures and low pressures.
  American Mineralogist 01/2008; 93:1903-1910. · 2.17 Impact Factor
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  Available from: Irina O Galuskina

  Article: The crystal structure of Si-deficient, oh-substituted, boron-bearing vesuvianite from the Wiluy River, Sakha-Yakutia, Russia

  Evgeny V Galuskin, Irina O Galuskina, Katarzyna Stadnicka, Thomas Armbruster, Marcin Kozanecki
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  ABSTRACT: The crystal structure of a Si-defi cient vesuvianite, space group P4/nnc, a 15.678(1), c 11.828(1) Å, from the Wiluy River, Sakha–Yakutia, Russia, has been refi ned from single-crystal X-ray data to R = 0.037. Electron-microprobe analyses indicate that this vesuvianite has only ca. 16 Si pfu in contrast to regular vesuvianite with 18 Si pfu. Site-occupancy refi nement yielded substantial vacancies at orthosilicate sites Z(1): 25% vacancies, Z(2): 16% vacancies. Vacancies at the tetrahedral site are associated with increased Z(1)–O and Z(2)–O distances, 1.687 and 1.660 Å, respectively. Vacancies and increased Z(1)–O and Z(2)–O bond lengths are consistent with hydrogarnet-type defects, where SiO 4 is replaced by H 4 O 4 tetrahedra. The single crystal investigated shows the highest hydrogarnet-type substitution analyzed by structure refi nement of vesuvianite. No vacancies were found involving the disilicate groups. Along the c axis, the increased size of Z(1) tetrahedra is balanced by a compression of the adjacent X(3) Ca-bearing dodecahedra. This structural fl exibility is the reason why the length of the c axis remains largely independent of the hydrogarnet-type substitution. A corresponding structural fl exibility does not exist along the a axis, leading to a systematic increase of a with increasing proportion of vacancies at the Si site. Polarized Raman spectra in the OH-stretching region are interpreted to indicate that hydrogarnet-type defects in vesuvianite lead to a more isotropic polarization of the absorp-tion bands at about 3650 cm –1 .
  The Canadian Mineralogist 01/2007; 45:239-248. · 1.12 Impact Factor
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  Available from: Irina O Galuskina

  Article: Chegemite Ca7 (SiO4) 3 (OH) 2-a new humite-group calcium mineral from the Northern Caucasus, Kabardino-Balkaria, Russia

  Evgeny V Galuskin, Viktor M Gazeev, Biljana Lazic, Thomas Armbruster, Irina O Galuskina, Aleksander E Zadov, Nikolai N Pertsev, Roman Wrzalik, Piotr Dzier, Zanowski, Anatoly G Gurbanov, Zyna Bzowska
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  ABSTRACT: The new mineral chegemite Ca 7 (SiO 4) 3 (OH) 2 (Pbnm, Z ¼ 4)1, a ¼ 5.0696(1), b ¼ 11.3955(1), c ¼ 23.5571(3) Å ; V ¼ 1360.91(4) Å 3 – the calcium and hydroxyl analogue of humite – was discovered as a rock-forming mineral in high-temperature skarns in calcareous xenoliths in ignimbrites of the Upper Chegem volcanic structure, Northern Caucasus, Kabardino-Balkaria, Russia. The chegemite forms granular aggregates with grain sizes up to 5 mm and is associated with various high-temperature minerals: larnite, spurrite, rondorfite, reinhardbraunsite, wadalite, lakargiite, and srebrodolskite, corresponding to the sanidinite metamorphic facies. The empirical formula of the holotype chegemite (mean of 68 analyses) is Ca 7 (Si 0.997 Ti 0.003 O 4) 3 (OH) 1.48 F 0.52 . Chegemite is characterized by the following optical properties: 2V Z ¼ À80(8) , a ¼ 1.621(2), b ¼ 1.626(3), g ¼ 1.630(2); Á ¼ 0.009; density D calc ¼ 2.892 g/cm 3 . The crystal structure, including hydrogen positions, has been refined from single-crystal MoKa X-ray diffraction data to R ¼ 2.2 %. Octahedral Ca–O distances are similar to those of g-Ca 2 SiO 4 (calcio-olivine). As is characteristic of OH-dominant humite-group minerals, two disordered H positions could be resolved. The main bands in the FTIR-spectra of chegemite are at 3550, and 437 cm À1 . Those in non-polarized Raman spectra are at 389, 403, 526, 818, 923.5, 3478, 3551 and 3563 cm À1 . The X-ray diffraction powder-pattern (FeKa-radiation) shows the strongest lines {d [Å ](I obs)} at: 1.907(10), 2.993(8), 2.700(8), 3.015(7), 2.720(7), 2.834(6), 3.639(5), and 3.040(5).
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  Available from: Irina O Galuskina

  Article: Dovyrenite Ca 6 Zr [Si 2 O 7] 2 (OH) 4-A New Mineral from Skarned Carbonate Xenoliths in Basic-Ultrabasic Rocks of the Ioko-Dovyren Massif, Northern Baikal …

  Evgeny V Galuskin, Nikolai N Pertsev, Thomas Armbruster, Milen Kadiyski, Aleksander E Zadov, Irina O Galuskina, Piotr Dzier¯anowski, Roman Wrzalik, Evgeny V Kislov
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  ABSTRACT: A b s t r a c t . Dovyrenite, simplified formula Ca 6 Zr[Si 2 O 7 ] 2 (OH) 4 , occurs as an accessory mineral in vein skarns developed in carbonate xenoliths in subvolcanic layered plagiodunite-troctolite series in the Ioko--Dovyren Massif of Proterozoic age, Northern Baikal Region, Buryatia, Russia. Dovyrenite is a late mineral of altered pyroxene and melilite-monticellite skarns. Associated minerals are Zr-bearing phases: fassaitic pyroxene, perovskite and hydrogarnets; and also monticellite, vesuvianite, diopside, foshagite, brucite, calzirtite, tazheranite, baghdadite, apatite, calcite, native bismuth, sphalerite, selenian galena, clausthalite, safflorite, rammelsbergite, pyrrhotite, pentlandite, valleriite, laitakarite, nickeline, nickel-skutterudite. The average structure of dovyrenite is orthorhombic, space group Pnnm, with subcell parameters A = 5.666(16) C, B = 18.844(5) C, C = 3.728(11) C, V = 398.0(2) C 3 and Z = 1. Dovyrenite shows a new type of modular structure with stacking of the tobermorite-like and the rosenbuschite-like layers parallel to (010). Single-crystal structural data point to an incompletely occupied Ca(2) site from the rosenbuschite module which is confirmed by microprobe analyses: ZrO 2 16.47, SiO 2 32.83, TiO 2 0.14, HfO 2 0.16, Cr 2 O 3 0.01, CaO 43.87, FeO 0.25, MgO 0.13, MnO 0.02, Nb 2 O 3 0.03; total 99.38 wt% with calculated H 2 O. The empirical formula is (Ca 5.73 Fe 0.03 Mg 0.02) S5.78 (Zr 0.98 Hf 0.01 Ti 0.01) S1 Si 4 (O 13.56 OH 0.44) S14 (OH) 4 . The presence of two types of OH group in the dovyrenite structure is corroborated by FTIR and Raman spectroscopy. Dovyrenite is an optically positive biaxial mineral: a 1.659(2), b 1.660(2); g 1.676(2); 2Vz 30(5)° (measured), 28° (calculated). The coexistence of monticellite, foshagite and dovyrenite points to a narrow interval of crystallization 560–630°C under subvolcanic conditions (P < 10 8 Pa).