Geochemistry of metamorphosed pillow basalts of the Chara Zone,NE Kazakhstan     

N. I. Volkova  V. V. Khlestov  V. P. Sukhorukov  M. V. Khlestov 《Doklady Earth Sciences》2016,467(2):350-354

Geochemical study of the metamorphosed pillow lavas of the Chara Zone revealed that their protoliths have N-MORB compositions. Elevated concentrations of K, Rb, Cs, and lower Ca may be related not to blueschist metamorphism, but rather they may be inherited from underwater alteration of parental basalts. Comparative analysis of the compositions of massive glaucophanites and vein rocks demonstrated the relative mobility of Sr, U, P, Ba, Rb, K, Cs, Ca, and LREEs, at least on the local scale. Their mobility has been provided by fluids circulating in the subduction zone, where the fluids have been generated through slab dehydratation processes. These studies of metamorphosed pillow lavas of the Chara Zone displayed only local alterations in the bulk composition of their protoliths, which evidences a low intensity of fluid flows: this allowed preservation of the geochemistry of oceanic basalts.  相似文献   

The Darriwilian acritarch assemblage from Ordovician deposits of the Arkhangelsk Oblast, the northern Russian Plate     

E. G. Raevskaya  N. A. Volkova  I. A. Sivertseva 《Stratigraphy and Geological Correlation》2006,14(4):386-398

Borehole 2506 drilled in the northern area of the Arkhangelsk Oblast penetrated through the Paleozoic sedimentary block isolated in the Vendian thick sequence. A diverse acritarch assemblage has been established within the depth interval of 119.9–217.5 m. The assemblage comprises more than 70 taxa, including species characteristic of the boundary interval between the Volkhov and Kunda horizons of the East European Platform (the graptolite Didymograptus hirundo Zone). Stratigraphic position of host deposits was established within the Darriwilian Stage of the Middle Ordovician. The described assemblage of microphytofossils is similar to coeval assemblages from NW Russia, Baltic region, and Scandinavia, being typical of the Baltic phytoplankton province of temperate latitudes. A great number of species in common suggests that the assemblage under consideration is correlative with coeval assemblages of southern China thus offering a possibility of remote correlation.  相似文献   

Geochemical signatures for eclogite protolith from the Maksyutov Complex, South Urals   总被引：2，自引：0，他引：2  

N. I. Volkova  A. E. Frenkel  V. I. Budanov  G. G. Lepezin 《Journal of Asian Earth Sciences》2004,23(5):745-759

We conducted a geochemical study of eclogites (40 samples) from a boudin of the Lower Unit of the Maksyutov Complex in the South Urals in order to determine their protolith nature. The eclogites have major element compositions corresponding to quartz-bearing hypersthene basalts. Trace-element characteristics of the eclogites further suggest that they resemble enriched-type of tholeiites such as E-MORB. The compositional variation of eclogites was likely caused by fractional crystallization of parental melt under hypabyssal conditions, during its intrusion in thinned continental crust shortly before subduction. The high-pressure metamorphism has not affected significantly the major- and trace-element signatures of the protoliths. The compositions of co-existing minerals from the distinguished rock groups do not show significant distinctions. The considerable scatter of P–T estimates of metamorphic conditions does not depend on whole-rock composition. Therefore, the eclogitization was preceded by a chemical differentiation of an initial magmatic source, which is responsible for co-existence of rocks of variable composition in the same boudin. Dikes or sills of tholeiite basalts having geochemical characteristics of E-MORB could be the protoliths for the Maksyutov eclogites.  相似文献   

Global sensitivity analysis for a numerical model of radionuclide migration from the RRC “Kurchatov Institute” radwaste disposal site   总被引：1，自引：1，他引：0  

E. Volkova  B. Iooss  F. Van Dorpe 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(1):17-31

Today, in different countries, there exist sites with contaminated groundwater formed as a result of inappropriate handling or disposal of hazardous materials or wastes. Numerical modeling of such sites is an important tool for a correct prediction of contamination plume spreading and an assessment of environmental risks associated with the site. Many uncertainties are associated with a part of the parameters and the initial conditions of such environmental numerical models. Statistical techniques are useful to deal with these uncertainties. This paper describes the methods of uncertainty propagation and global sensitivity analysis that are applied to a numerical model of radionuclide migration in a sandy aquifer in the area of the RRC “Kurchatov Institute” radwaste disposal site in Moscow, Russia. We consider 20 uncertain input parameters of the model and 20 output variables (contaminant concentration in the observation wells predicted by the model for the end of 2010). Monte Carlo simulations allow calculating uncertainty in the output values and analyzing the linearity and the monotony of the relations between input and output variables. For the non monotonic relations, sensitivity analyses are classically done with the Sobol sensitivity indices. The originality of this study is the use of modern surrogate models (called response surfaces), the boosting regression trees, constructed for each output variable, to calculate the Sobol indices by the Monte Carlo method. It is thus shown that the most influential parameters of the model are distribution coefficients and infiltration rate in the zone of strong pipe leaks on the site. Improvement of these parameters would considerably reduce the model prediction uncertainty.  相似文献   

Variation of Carboneceous Atmospheric Aerosol Near St. Petersburg     

Vlasenko  S. S.  Volkova  K. A.  Ionov  D. V.  Ryshkevich  T. I.  Ivanova  O. A.  Mikhailov  E. F. 《Izvestiya Atmospheric and Oceanic Physics》2019,55(6):619-627

Izvestiya, Atmospheric and Oceanic Physics - The results of 5-year (2013–2017) measurements of organic (OC) and elemental (EC) carbon aerosol fractions observed at the atmospheric monitoring...  相似文献   

Intercalibration of Bruevich’s method to determine the total alkalinity in seawater     

G. Yu. Pavlova  P. Ya. Tishchenko  T. I. Volkova  A. Dickson  K. Wallmann 《Oceanology》2008,48(3):438-443

In 2000, the Carbon Dioxide in the Ocean working group of the North Pacific Marine Science Organization (PICES) performed an international experiment on the intercalibration of the measurements of the total alkalinity in seawater using certified reference materials (CRM). Taking part in this experiment, Russian specialists presented the method by Bruevich. The results of the intercalibration showed that the alkalinity values obtained by Bruevich’s method using modern burettes, an Na₂CO₃ reactant of high purity as a standard to ascertain the acid titre, and corrections for the acid density and for the weights of the acid and seawater samples in vacuum are in agreement with the standard within ±1 μ M/kg.  相似文献   

Quantitative biome reconstruction using modern and late Quaternary pollen data from the southern part of the Russian Far East     

Lyudmila Mokhova  Pavel Tarasov  Valentina Bazarova  Mikhail Klimin 《Quaternary Science Reviews》2009,28(25-26):2913-2926

In this study we present a recent compilation of 286 modern surface pollen spectra from the southern part of the Russian Far East (42–54°N, 131–141°E) and use it to test the biome reconstruction method. Seventy terrestrial pollen taxa were assigned to plant functional types and then classified to eight regional biomes. When applied to 286 surface pollen spectra, the method assigns about 70% (201 sites) of the samples to the cool mixed forest biome, 17% – to the taiga, 2% – to the cool conifer forest, 3% – to the temperate deciduous forest, and 7% – to the steppe. The steppe reconstruction is characteristic of the pollen spectra from the agricultural areas around Lake Khanka. A visual comparison shows good agreement between pollen-derived biomes and actual vegetation distribution in the region. However, pollen and botanical data, compared with the potential vegetation distribution simulated from the modern climate dataset using the BIOME1 model, demonstrate that spatial distribution of cool mixed forest is underrepresented in the model simulation. The model sets the mean temperature of the coldest month of −15 °C as the factor limiting distribution of the temperate deciduous broadleaf taxa, while vegetation and pollen data from the region demonstrate that this limit should be lowered to −26 °C. Application of the method to the Gur 3–99 pollen record (50°00^′N, 137°03^′E) demonstrates that tundra vegetation predominated around the site prior to 14 ka BP (1 ka = 1000 cal. years). However, the local presence of boreal trees and mixed forest-tundra vegetation is suggested by relatively high taiga scores. Soon after 14 ka BP the scores of taiga become slightly higher than tundra scores. During 11.4–10.5 ka BP a cool conifer forest is reconstructed. Establishment of the full interglacial conditions is marked by the onset of cool mixed forest by 10.5 ka BP. Between 10.3 and 2.5 ka BP the scores of temperate deciduous forest are close to those of cool mixed forest and become distinctly lower during the late Holocene.  相似文献   

X-ray study of the graphite-bearing rocks from the Pestpaksha ore occurrence and structural features of graphite     

S. A. Volkova  O. M. Il’icheva  O. B. Kuznetsov 《Lithology and Mineral Resources》2011,46(4):363-368

Graphite-bearing rocks and graphites from the Precambrian metamorphic sequence of the Pestpaksha ore occurrence, Murmansk district, have been studied by the X-ray method. It was determined that the rocks have a complex polycomponent composition. Graphite is associated with garnet-quartz, pyroxene-amphibole, and biotite-quartz with an admixture of pyrrhotite, kyanite, chlorite, and other minerals. In terms of mineral composition, the studied samples are subdivided into five groups. The structural characteristics of graphite—parameters a ₀ and c ₀, the degree of structural perfection (U), the content of rhombohedral phase (R), and others—were found to be different for each group. The U value varies from 1.04 to 1.56 (with predominant values from 1.4 to 1.5), while the content of rhombohedral phase in samples is no more than 18%. This fact indicates a relatively high 3D order, which is typical of graphites from metamorphic rocks. Graphites from metasomatites have the lowest U value, while those from weathering zones are characterized by a small value of the coherent scattering domain (CSD). It was established that interplanar spacing d ₀₀₂ of graphite correlates with depth, while the degree of ductility and flexibility of the graphite is defined by conditions of its retrograde metamorphism.  相似文献   

On the Connection between the 2008–2009 Activation of the Koryakskii Volcano and Deep Magmatic Processes     

Mikhailov  V. O.  Volkova  M. S.  Timoshkina  E. P.  Shapiro  N. M.  Smirnov  V. B. 《Izvestiya Physics of the Solid Earth》2021,57(6):819-824

Izvestiya, Physics of the Solid Earth - Abstract—The last activation of the Koryakskii volcano in 2008–2009 was accompanied by intense fumarolic and seismic activity. Volcanic activity...  相似文献   

Eclogites in the Chara zone,NE Kazakhstan: New geochemical and geochronological data     

N. I. Volkova  V. A. Simonov  A. V. Travin  S. I. Stupakov  D. S. Yudin 《Geochemistry International》2016,54(2):208-214

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