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Rakov L.T.,RAS Institute of Geology and Mineralogy | Dubinchuk V.T.,Fedorovskii All Russia Institute of Mineral Resources
Geochemistry International | Year: 2012

The influence of structural defects on the polymorphic transformations in quartz was studied by electron paramagnetic resonance and electron microscopy. It was established that the kinetics of the accumulation of the clusters of the β-phase depends on isomorphic impurities in quartz. It was confirmed that germanium ions and vacancies in quartz participate in the formation of the clusters. Obtained results allow the assumption that the amount of germanium required to preserve clusters increases with increasing temperature and vice versa. An explanation is presented for experimentally observed decomposition of clusters during artificial heating of some quartz samples. It was found that the clusters of the β-phase are autonomous units, i. e. may exist independently of host crystalline structure of quartz. The possible mechanism of influence of Ge impurity on the temperature of α-β-transition in quarts is discussed. © 2012 Pleiades Publishing, Ltd. Source


Bergman I.A.,Fedorovskii All Russia Institute of Mineral Resources | Kolesov G.M.,RAS Vernadsky Institute of Geochemistry and Analytical Chemistry
Geochemistry International | Year: 2012

As part of our ongoing research on the application of elemental geochemistry methods to Early Precambrian ferrous quartzite formations and in order to elucidate the nature of their ore material, we investigated the distribution of As, Sb, and Bi in exogenic oxide-hydroxide iron ores, sedimentary carbonate rocks and iron ores, and ferro-siliceous formations of the Krivoi Rog (Ukrainian shield), Kursk-Belgorod (Voronezh crystalline massif), Kostomuksha, and Imandra iron ore provinces (Baltic shield) of the Late Archean and Early Proterozoic. The results of the elemental geochemical investigations were used to evaluate the plausibility of some geological and geochemical models of Early Precambrian ferro-siliceous ore formation. © 2012 Pleiades Publishing, Ltd. Source


Baturin G.N.,RAS Shirshov Institute of Oceanology | Dubinchuk V.T.,Fedorovskii All Russia Institute of Mineral Resources
Geochemistry International | Year: 2011

The mineral and chemical compositions of a set of crust samples collected from the North, Central and South Atlantic were examined by means of analytical electron microscopy and ICP-MS, chemical, and microchemical elemental analysis. The dominant mineral phases of the crusts are vernadite, asbolane, and goethite, with minor ferrihydrite, and rare hematite and feroxyhyte. The samples show wide variability in major and trace elements; however, their characteristic geochemical signatures indicate hydrogenetic origin. A comparison between the compositions of oceanic hydrogenetic and hydrothermal crusts and metalliferous hydrothermal sediments from different ocean areas suggests that the geochemical approach may be insufficient in some cases and fail to identify a hydrothermal input in ferromanganese crusts of a mixed composition. © 2011 Pleiades Publishing, Ltd. Source


Lugovskaya I.G.,Fedorovskii All Russia Institute of Mineral Resources | Anufrieva S.I.,Fedorovskii All Russia Institute of Mineral Resources | Krylov I.O.,Fedorovskii All Russia Institute of Mineral Resources | Krylova A.V.,Mendeleev University of Chemical Technology
Petroleum Chemistry | Year: 2010

Using model catalytic reactions of n-hexane conversion and the conversions of both narrow and wide fractions of actual hydrocarbon mixtures, straight-run gasoline and gas condensate, as an example, it has been shown that modified type-III shungite rock (carbon content of 20-35%) from the Zazhogino deposit of Karelia at certain temperatures exhibited catalytic activity in the isomerization reaction of hydrocarbons with or without the insignificant formation of environmentally hazardous aromatic compounds. In the case of n-hexane and, especially, straight-run gasoline, the octane rating of the product increases. © 2010 Pleiades Publishing, Ltd. Source

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