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Sergey N. Britvin - One of the best experts on this subject based on the ideXlab platform.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 1: Neso-, cyclo-, ino- and phyllosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This is the initial paper in a pair of articles devoted to silicate minerals from fumaroles of the Tolbachik volcano (Kamchatka, Russia). These papers contain the first systematic data on silicate mineralization of fumarolic genesis. In this article Nesosilicates (forsterite, andradite and titanite), cyclosilicate (a Cu,Zn-rich analogue of roedderite), inosilicates (enstatite, clinoenstatite, diopside, aegirine, aegirine-augite, esseneite, “Cu,Mg-pyroxene”, wollastonite, potassic-fluoro-magnesio-arfvedsonite, potassic-fluoro-richterite and litidionite) and phyllosilicates (fluorophlogopite, yanzhuminite, “fluoreastonite” and the Sn analogue of dalyite) are characterized with a focus on chemistry, crystal-chemical features and occurrence. Unusual As5+ -rich varieties of forsterite, andradite, titanite, pyroxenes, amphiboles and mica are described. General data on silicate-bearing active fumaroles and the diversity and distribution of silicates in fumarole deposits are reported. Evidence for the fumarolic origin of silicate mineralization is discussed.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 2: Tectosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This second of two companion articles devoted to silicate mineralization in fumaroles of the Tolbachik volcano (Kamchatka, Russia) reports data on chemistry, crystal chemistry and occurrence of tectosilicates: sanidine, anorthoclase, ferrisanidine, albite, anorthite, barium feldspar, leucite, nepheline, kalsilite, sodalite and hauyne. Chemical and genetic features of fumarolic silicates are also summarized and discussed. These minerals are typically enriched with “ore” elements (As, Cu, Zn, Sn, Mo, W). Significant admixture of As5+ (up to 36 wt % As2O5 in sanidine) substituting Si is the most characteristic. Hauyne contains up to 4.2 wt % MoO3 and up to 1.7 wt % WO3 . All studied silicates are hydrogen-free, including mica and amphiboles which are F-rich. Iron-bearing minerals contain only Fe3+ due to strongly oxidizing formation conditions. In Tolbachik fumaroles, silicates were formed in the temperature range 500–800 ∘ C as a result of direct deposition from the gas phase (as volcanic sublimates) or gas–rock interactions. The zonation in distribution of major silicate minerals observed in a vertical section of the Arsenatnaya fumarole, from deep (the hottest) to upper parts is diopside + forsterite + enstatite + andradite → diopside → fluorophlogopite + diopside → sanidine + fluorophlogopite → sanidine. This is in agreement with volatilities of major species-defining metals in volcanic gases. From a crystal-chemical viewpoint, this series corresponds to the following sequence of crystallization of minerals with temperature decrease: Nesosilicates → inosilicates → phyllosilicates → tectosilicates.
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synthesis and crystal structure of the first thallium hydrous Nesosilicate tl4sio4 0 5h2o
Zeitschrift für anorganische und allgemeine Chemie, 2009Co-Authors: Sergey N. Britvin, Oleg I. Siidra, Sergey V. Krivovichev, Wulf DepmeierAbstract:Orange prismatic crystals of the first thallium hydrous Nesosilicate Tl(4)SiO(4)center dot 0.5H(2)O have been obtained by evaporation from aqueous Solution. There are three symmetrically independent Tl(+) cations and five symmetrically independent oxygen atoms in the structure of Tl(4)SiO(4)center dot 0.5H(2)O. The O(4) and O(5) atoms belong to water molecules. Coordination polyhedra of the Tl(+) cations are strongly distorted because of the stereoactive behavior of lone electron pairs. The structure of Tl(4)SiO(4)center dot 0.5H(2)O contains sheets of SiO(4) tetrahedra and Tl coordination polyhedra. The sheets have the composition [Tl(3)SiO(4)](-) and are parallel to [100]. Within the sheets, SiO(4) tetrahedra link to thallium polyhedra though common corners. The sheets are linked by dimers of face-sharing Tl(3)O(5) polyhedra. thus providing interconnection of the sheets into a framework. The framework has large elliptical channels occupied by water molecules (OW2) and electron pairs of Tl(+) cations. The comparison with some other M(+) (M = K, Ag, Tl) silicates is given.
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Synthesis and Crystal Structure of the First Thallium Hydrous Nesosilicate Tl4SiO4·0.5H2O
Zeitschrift für anorganische und allgemeine Chemie, 2009Co-Authors: Sergey N. Britvin, Oleg I. Siidra, Sergey V. Krivovichev, Wulf DepmeierAbstract:Orange prismatic crystals of the first thallium hydrous Nesosilicate Tl(4)SiO(4)center dot 0.5H(2)O have been obtained by evaporation from aqueous Solution. There are three symmetrically independent Tl(+) cations and five symmetrically independent oxygen atoms in the structure of Tl(4)SiO(4)center dot 0.5H(2)O. The O(4) and O(5) atoms belong to water molecules. Coordination polyhedra of the Tl(+) cations are strongly distorted because of the stereoactive behavior of lone electron pairs. The structure of Tl(4)SiO(4)center dot 0.5H(2)O contains sheets of SiO(4) tetrahedra and Tl coordination polyhedra. The sheets have the composition [Tl(3)SiO(4)](-) and are parallel to [100]. Within the sheets, SiO(4) tetrahedra link to thallium polyhedra though common corners. The sheets are linked by dimers of face-sharing Tl(3)O(5) polyhedra. thus providing interconnection of the sheets into a framework. The framework has large elliptical channels occupied by water molecules (OW2) and electron pairs of Tl(+) cations. The comparison with some other M(+) (M = K, Ag, Tl) silicates is given.
Eugeny G. Sidorov - One of the best experts on this subject based on the ideXlab platform.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 1: Neso-, cyclo-, ino- and phyllosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This is the initial paper in a pair of articles devoted to silicate minerals from fumaroles of the Tolbachik volcano (Kamchatka, Russia). These papers contain the first systematic data on silicate mineralization of fumarolic genesis. In this article Nesosilicates (forsterite, andradite and titanite), cyclosilicate (a Cu,Zn-rich analogue of roedderite), inosilicates (enstatite, clinoenstatite, diopside, aegirine, aegirine-augite, esseneite, “Cu,Mg-pyroxene”, wollastonite, potassic-fluoro-magnesio-arfvedsonite, potassic-fluoro-richterite and litidionite) and phyllosilicates (fluorophlogopite, yanzhuminite, “fluoreastonite” and the Sn analogue of dalyite) are characterized with a focus on chemistry, crystal-chemical features and occurrence. Unusual As5+ -rich varieties of forsterite, andradite, titanite, pyroxenes, amphiboles and mica are described. General data on silicate-bearing active fumaroles and the diversity and distribution of silicates in fumarole deposits are reported. Evidence for the fumarolic origin of silicate mineralization is discussed.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 2: Tectosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This second of two companion articles devoted to silicate mineralization in fumaroles of the Tolbachik volcano (Kamchatka, Russia) reports data on chemistry, crystal chemistry and occurrence of tectosilicates: sanidine, anorthoclase, ferrisanidine, albite, anorthite, barium feldspar, leucite, nepheline, kalsilite, sodalite and hauyne. Chemical and genetic features of fumarolic silicates are also summarized and discussed. These minerals are typically enriched with “ore” elements (As, Cu, Zn, Sn, Mo, W). Significant admixture of As5+ (up to 36 wt % As2O5 in sanidine) substituting Si is the most characteristic. Hauyne contains up to 4.2 wt % MoO3 and up to 1.7 wt % WO3 . All studied silicates are hydrogen-free, including mica and amphiboles which are F-rich. Iron-bearing minerals contain only Fe3+ due to strongly oxidizing formation conditions. In Tolbachik fumaroles, silicates were formed in the temperature range 500–800 ∘ C as a result of direct deposition from the gas phase (as volcanic sublimates) or gas–rock interactions. The zonation in distribution of major silicate minerals observed in a vertical section of the Arsenatnaya fumarole, from deep (the hottest) to upper parts is diopside + forsterite + enstatite + andradite → diopside → fluorophlogopite + diopside → sanidine + fluorophlogopite → sanidine. This is in agreement with volatilities of major species-defining metals in volcanic gases. From a crystal-chemical viewpoint, this series corresponds to the following sequence of crystallization of minerals with temperature decrease: Nesosilicates → inosilicates → phyllosilicates → tectosilicates.
Yuchun Zhai - One of the best experts on this subject based on the ideXlab platform.
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Reaction pathway led by silicate structure transformation on decomposition of CaSiO3 in alkali fusion process using NaOH
Transactions of Nonferrous Metals Society of China, 2015Co-Authors: Chang-ming Zhao, Guo-cheng Wang, Ai Xingang, Zi-rui Wang, Li Shengli, Yuchun ZhaiAbstract:Abstract The mechanism of decomposition of calcium inosilicate (CaSiO3) synthesized through chemical deposition method using analytical reagent NaSiO3?9H2O and CaCl2 during the alkali fusion process using NaOH was investigated by Raman spectroscopy in situ, X-ray diffraction and Fourier transform infrared spectrometer (FTIR). The results show that the tetrahedral silica chains within CaSiO3 are gradually disrupted and transformed into Nesosilicate with the isolated SiO4 tetrahedra at the beginning of the alkali fusion process. The three intermediates including Ca2SiO4, Na2CaSiO4 and Na2SiO3 appear simultaneously in the decomposition of CaSiO3, while the final products are Ca(OH)2 and Na4SiO4. It can be concluded that there exist two reaction pathways in the alkali fusion process of CaSiO3: one is ion exchange, the other is in the main form of the framework structure change of silicate. The reaction pathway is led by silicate structure transformation in the alkali fusion process.
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An in situ spectroscopic study on decomposition of MgSiO3 during the alkali fusion process using sodium hydroxide
New Journal of Chemistry, 2014Co-Authors: Min Xu, Zi-rui Wang, Jinglin You, Qian Xu, Qiushi Song, Yuchun ZhaiAbstract:The mechanism of decomposition of magnesium inosilicate (MgSiO3) during the alkali fusion process using NaOH was investigated by Raman spectroscopy in situ and X-ray diffraction analyses. The results show that the tetrahedral silica chains within MgSiO3 are gradually disrupted, and Nesosilicate with the isolated SiO4 tetrahedra becomes reorganized at the beginning of the alkali fusion process. In the decomposition of MgSiO3, the two intermediates are Mg2SiO4 and Na2MgSiO4, while the final products are Mg(OH)2 and Na4SiO4. It can be concluded that this decomposition did not initiate from the cation exchange reaction in the process.
Nadezhda V. Shchipalkina - One of the best experts on this subject based on the ideXlab platform.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 1: Neso-, cyclo-, ino- and phyllosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This is the initial paper in a pair of articles devoted to silicate minerals from fumaroles of the Tolbachik volcano (Kamchatka, Russia). These papers contain the first systematic data on silicate mineralization of fumarolic genesis. In this article Nesosilicates (forsterite, andradite and titanite), cyclosilicate (a Cu,Zn-rich analogue of roedderite), inosilicates (enstatite, clinoenstatite, diopside, aegirine, aegirine-augite, esseneite, “Cu,Mg-pyroxene”, wollastonite, potassic-fluoro-magnesio-arfvedsonite, potassic-fluoro-richterite and litidionite) and phyllosilicates (fluorophlogopite, yanzhuminite, “fluoreastonite” and the Sn analogue of dalyite) are characterized with a focus on chemistry, crystal-chemical features and occurrence. Unusual As5+ -rich varieties of forsterite, andradite, titanite, pyroxenes, amphiboles and mica are described. General data on silicate-bearing active fumaroles and the diversity and distribution of silicates in fumarole deposits are reported. Evidence for the fumarolic origin of silicate mineralization is discussed.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 2: Tectosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This second of two companion articles devoted to silicate mineralization in fumaroles of the Tolbachik volcano (Kamchatka, Russia) reports data on chemistry, crystal chemistry and occurrence of tectosilicates: sanidine, anorthoclase, ferrisanidine, albite, anorthite, barium feldspar, leucite, nepheline, kalsilite, sodalite and hauyne. Chemical and genetic features of fumarolic silicates are also summarized and discussed. These minerals are typically enriched with “ore” elements (As, Cu, Zn, Sn, Mo, W). Significant admixture of As5+ (up to 36 wt % As2O5 in sanidine) substituting Si is the most characteristic. Hauyne contains up to 4.2 wt % MoO3 and up to 1.7 wt % WO3 . All studied silicates are hydrogen-free, including mica and amphiboles which are F-rich. Iron-bearing minerals contain only Fe3+ due to strongly oxidizing formation conditions. In Tolbachik fumaroles, silicates were formed in the temperature range 500–800 ∘ C as a result of direct deposition from the gas phase (as volcanic sublimates) or gas–rock interactions. The zonation in distribution of major silicate minerals observed in a vertical section of the Arsenatnaya fumarole, from deep (the hottest) to upper parts is diopside + forsterite + enstatite + andradite → diopside → fluorophlogopite + diopside → sanidine + fluorophlogopite → sanidine. This is in agreement with volatilities of major species-defining metals in volcanic gases. From a crystal-chemical viewpoint, this series corresponds to the following sequence of crystallization of minerals with temperature decrease: Nesosilicates → inosilicates → phyllosilicates → tectosilicates.
Lorenzo Fernández - One of the best experts on this subject based on the ideXlab platform.
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dehydration and rehydration processes of cement paste exposed to high temperature environments
Journal of Materials Science, 2004Co-Authors: Corinne Alonso, Lorenzo FernándezAbstract:Microstructural changes of an OPC cement paste after being exposed at various elevated temperatures and further rehydration have been evaluated using 29Si MAS-NMR. Thermogravimetry and XRD are also employed to complement the information. NMR studies of cement paste exposed to high temperatures demonstrate a progressive transformation of C-S-H gel that leads at 450°C, to a modified C-S-H gel. For temperatures above 200°C to a progressive formation of a new Nesosilicate. At 750°C, the transformation of C-S-H is complete into the Nesosilicate form with a C2S stoichiometry close to larnite, but less crystalline. Also is observed an increase of portlandite that takes place up to temperatures of 200°C. A progressive increase of calcite formation up to 450°C is noticed. The ettringite disappearance below 100°C is confirmed and the portlandite and calcite are converted to lime at 750°C. The initial anhydrous phases as larnite and brownmillerite remain unaltered during heating. Rehydration of the heated samples (450 and 750°C) shows recrystallization of calcite, portlandite and ettringite, and the C-S-H reformation from the new Nesosilicate. The larnite and brownmillerite remain unaltered during rehydration. The developing of damaged due to the formation of microcracking is detected and improved because of rehydration phenomena.