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Stanevich A.M.,Russian Academy of Sciences | Mazukabzov A.M.,Russian Academy of Sciences | Kornilova T.A.,Russian Academy of Sciences | Maksimova E.N.,Irkutsk State Pedagogical University
Lithology and Mineral Resources | Year: 2012

First finds of microfossils from the silicified microphytolitic carbonates of the Uluntui Formation in the southwestern Baikal region are described. They are represented by remains of the cyanobacterial community that formed microphytolites. These microfossils are accompanied by acritarchs probably belonging to green algae. The silicified microfossils are sufficiently well preserved despite complete and repeated recrystallization of host primary carbonate rocks. Main phases of secondary mineralization are related to hydrothermal-metasomatic processes, which were likely provoked by collisional events on the southern flank of the Siberian Craton in the Silurian. © 2012 Pleiades Publishing, Ltd.


Voronkov M.G.,Favorsky Irkutsk Institute of Chemistry | Korlyukov A.A.,RAS Nesmeyanov Institute of Organoelement Compounds | Zel'bst E.A.,Irkutsk State Pedagogical University | Grebneva E.A.,Favorsky Irkutsk Institute of Chemistry | And 2 more authors.
Journal of Structural Chemistry | Year: 2010

X-ray diffraction is used to determine the crystal and molecular structure of spirocyclic (C=O→Si←O′=C′) bis(2-methyl-4-pyrone-3-oxy)difluoro(λ6)siliconium containing a hypervalent silicon atom and the previously unknown F2SiO4 coordination center. The coordination polyhedron of the silicon atom is a slightly distorted octahedron. © 2009 Springer Science+Business Media, Inc.


Korlyukov A.A.,RAS Nesmeyanov Institute of Organoelement Compounds | Antipin M.Y.,RAS Nesmeyanov Institute of Organoelement Compounds | Buzin M.I.,RAS Nesmeyanov Institute of Organoelement Compounds | Zel'bst E.A.,Irkutsk State Pedagogical University | And 3 more authors.
Journal of Structural Chemistry | Year: 2010

Using X-ray diffraction the presence of two phases of 1-fluorosilatrane (FSa) is stated and the specific features of their spatial structure are studied. Phase transition occurs at 156-158 K and is characterized by low energy. In the low-temperature phase, four crystallographically independent molecules are ordered, while in the high-temperature phase one of two independent molecules has disordered carbon β-atoms. A quantum chemical analysis of crystal packing in the low-temperature FSa phase is performed. The estimated value of the coordination N→Si bond strength in the crystal is 29. 2 kcal/mol. The charge distribution indicates the localization of valence electron density around the O3SiF fragment. © 2009 Springer Science+Business Media, Inc.


Voronkov M.G.,RAS Institute of Chemistry | Korlyukov A.A.,RAS Nesmeyanov Institute of Organoelement Compounds | Zelbst E.A.,Irkutsk State Pedagogical University | Knyazev S.P.,RAS Nesmeyanov Institute of Organoelement Compounds | And 3 more authors.
Journal of Structural Chemistry | Year: 2010

The crystal structures of anhydrous 1-germatranol and its complex with HCCl 3 are centrosymmetrical dimers because of their intermolecular hydrogen bonds. In the germatranol crystal, the axial and equatorial oxygen atoms of its two molecules are hydrogen bonded into an eight-membered coordination cycle. In the complex with HCCl 3, the two molecules of germatranol are likewise linked in dimers, and both axial oxygen atoms are H bonded with HCCl 3. In the investigated structures, the axial Ge-O bond is shorter than the equatorial ones. Depending on the number and strength of the hydrogen bonds, the interatomic Ge-O and Ge ← N distances change markedly. The quantitative estimates of the H bond energy are obtained from quantum chemical calculations of the model systems containing 1-germatranol and HCCl 3 molecules. © 2010 Pleiades Publishing, Ltd.


Kulikova N.N.,Russian Academy of Sciences | Suturin A.N.,Russian Academy of Sciences | Saibatalova E.V.,Russian Academy of Sciences | Boiko S.M.,Russian Academy of Sciences | And 3 more authors.
Geochemistry International | Year: 2011

Based on materials collected in 2003-2007, data on aquatic lichens of the genus Verrucaria from the rocky littoral zone of Lake Baikal are discussed. The maximum density of their occurrence was observed at a depth of 1.5 m; 95-100% of rock fragments recovered from depths of 1. 5-2.2 m are encrusted by 24-43% with the thalli of Verrucaria spp. It was found that the lichens contribute actively to the physical and physicochemical weathering of their rock substrate and prefer to reside on the rocks of granitic composition. The chemical composition of aquatic verrucaria is dominated by the same elements that are most abundant in the rocks (Ca > K > Fe > Al > Mg > P > S > Na > Mn > Sr > Ba), and, in most cases, the characteristic element ratios of the rock compositions are preserved in the composition of the thalli of Verrucaria spp. Compared with the elemental composition of the near-bottom water layer, the lichens most extensively concentrate the elements that slowly migrate in water: Gd > Sm > Pr > Nd > Al > La > Dy > Tb > Y > Lu > Ce > Yb > Be > Tm > Co > Nb > Mn > Zn. Compared with the composition of rocks, the mineral composition of the thalli of Verrucaria spp. is enriched by a factor of 100-10 in Hg > As > P > Zn > Li > S > U > Mo > Se > Cd > Ca > Tl > Sr > Pb > Be. © 2011 Pleiades Publishing, Ltd.

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