<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">Dovyrenite, simplified formula Ca6Zr[Si2O7]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 <italic>Pnnm</italic>, with subcell parameters <italic>A</italic> = 5.666(16) Å, <italic>B</italic> = 18.844(5) Å, <italic>C</italic> = 3.728(11) Å, <italic>V</italic> = 398.0(2) Å3 and <italic>Z</italic> = 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: ZrO2 16.47, SiO2 32.83, TiO2 0.14, HfO2 0.16, Cr2O3 0.01, CaO 43.87, FeO 0.25, MgO 0.13, MnO 0.02, Nb2O3 0.03; total 99.38 wt% with calculated H2O. The empirical formula is (Ca5.73Fe0.03Mg0.02)σ5.78(Zr0.98Hf0.01Ti0.01)σ1Si4(O13.56OH0.44)σ14(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: α 1.659(2), β 1.660(2); γ 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 &lt; 108 Pa).</abstract>

Dovyrenite, simplified formula Ca6Zr[Si2O7]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) Å, B = 18.844(5) Å, C = 3.728(11) Å, V = 398.0(2) Å3 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: ZrO2 16.47, SiO2 32.83, TiO2 0.14, HfO2 0.16, Cr2O3 0.01, CaO 43.87, FeO 0.25, MgO 0.13, MnO 0.02, Nb2O3 0.03; total 99.38 wt% with calculated H2O. The empirical formula is (Ca5.73Fe0.03Mg0.02)σ5.78(Zr0.98Hf0.01Ti0.01)σ1Si4(O13.56OH0.44)σ14(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: α 1.659(2), β 1.660(2); γ 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 < 108 Pa).

Dovyrenite Ca6Zr[Si2O7]2(OH)4 - A New Mineral from Skarned Carbonate Xenoliths in Basic-Ultrabasic Rocks of the Ioko-Dovyren Massif, Northern Baikal Region, Russia

Faculty of Earth Sciences, Department of Geochemistry, Mineralogy and Petrography, University of Silesia, Będzińska 60, 41-200 Sosnowiec, Poland

Institute of Geology of Ore Deposits, Geochemistry, Mineralogy and Petrography (IGEM) RAS, Staromonetny 35, Moscow, Russia

Mineralogical Crystallography, Institute of Geological Sciences, University of Bern, Freiestr. 3, CH-3012 Bern, Switzerland

Sci.-Research Center "NEOCHEM", Altuf'evskoye Highway 43, Moscow, Russia

Institute of Geochemistry, Mineralogy and Petrology, Warsaw University, al. Żwirki i Wigury 93, 02-089 Warszawa, Poland

Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland

Institute of Geology, Siberian Branch, RAS, Sakhyanova Str. 6, 670042 Ulan-Ude, Russia

Mineralogia

Dovyrenite CaZr[SiO](OH) - A New Mineral from Skarned Carbonate Xenoliths in Basic-Ultrabasic Rocks of the Ioko-Dovyren Massif, Northern Baikal Region, Russia

Dovyrenite, simplified formula Ca6Zr[Si2O7]2(OH)4, occurs as an accessory mineral in vein skarns developed in carbonate xenoliths in subvolcanic layered...

Dovyrenite Ca₆Zr[Si₂O₇]₂(OH)₄ - A New Mineral from Skarned Carbonate Xenoliths in Basic-Ultrabasic Rocks of the Ioko-Dovyren Massif, Northern Baikal Region, Russia

Pubblicato online: 03 lug 2007

Pagine: 15 - 28

DOI: https://doi.org/10.2478/v10002-007-0012-y

Parole chiave
dovyrenite, new mineral, structure, FTIR, Raman, skarn, xenoliths, Ioko-Dovyren Massif, Buryatia, Russia

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