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A. I. Ryabinin V. F. Andryushchenko N. A. Konovalenko L. V. Savina S. A. Shibayeva 《Physical Oceanography》1996,7(3):209-216
In July–August 1993, 41 samples of the Dnieper liman bottom sediments were taken at nine stations occupied by the State Service
for Monitoring and Control of the Marine Environment. Chemical analysis of strontium-90, radium-226, thorium-232, calcium,
and stable strontium concentrations was performed. Strontium-90 was found to be non-monotonically distributed in the interiors
of bottom sediments down to a depth of 100–120 cm. Correlation analysis carried out, for individual pairs of the components
showed the level of relationship between them to be statistically significant. The content of Sr-90 has been determined.
Translated by Vladimir A. Puchkin. 相似文献
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A. A. Vorontsov G. S. Fedoseev S. V. Andryushchenko Yu. A. Pakhol’chenko 《Doklady Earth Sciences》2011,441(2):1649-1655
The results of geochemical and isotopic (Sr-Nd) studies of the rocks comprising the structure of igneous associations of Minusa
Trough are presented. They allowed us to identify the heterogeneity of igneous sources. Similar heterogeneity is determined
by mixing of at least two sources of source melts. The first one corresponds, by the geochemical parameters, to the OIB composition
with a high content of noncoherent lithophile elements and to the PREMA-type mantle in its isotopic parameters. Another source
is comparable to the lithospheric mantle that was metasomatized in above-subduction conditions. Participation of a second
source melt in magma formation led to the appearance of IAB geochemical features (typical depletion in high-charge hydrophobic
Ti, Nb, and Ta, and enrichment in Ba, common and radiogenic Sr) for basite melts. The performed studies give us ground to
attribute the magmatism of Minusa Trough to the Altai-Sayan plume evolution beneath the convergent boundary within the limits
of the southwestern margin of the Siberian continent. 相似文献
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A.A. Vorontsov G.S. Fedoseev S.V. Andryushchenko 《Russian Geology and Geophysics》2013,54(9):1001-1025
Based on geological data and the geochemical and isotopic (Sr, Nd) parameters of the Devonian volcanic associations of the Minusa basin, the main regularities of volcanism development are considered, the composition of magmatic sources is studied, and the geodynamic mechanisms of their involvement in rifting are reconstructed. The early stage of formation of the Minusa basin was characterized by intense volcanism, which resulted in differentiated and, more seldom, bimodal volcanic complexes composed of pyroclastic rocks and dolerite sills. At the late stage, only terrigenous deposits accumulated in the basin. It has been established that the basites are similar in composition and are intermediate in geochemical characteristics between intraplate rocks (OIB) and continent-marginal ones (IAB). The basites, like OIB, have high contents of all lithophile elements, which is typical of enriched mantle sources, and, like IAB, show negative anomalies of Nb, Ta, Ti, and, to a smaller extent, Rb, Th, Zr, and Hf, selective enrichment in Pb and Ba (and, sometimes, Sr), and a weak REE differentiation (7 < (La/Yb)N < 17). In contrast to the basins in other segments of the Devonian Altai–Sayan rift area, the igneous associations in the Minusa basin are characterized by a worse expressed geochemical inhomogeneity of rocks and lack of high-Ti (> 2 wt.% TiO2) basites. The Sr and Nd isotope compositions of the Minusa basites deviate from the mantle rock series toward the compositions with high radiogenic-strontium and low REE contents.This points to the melting of a mantle substratum (PREMA-type) and carbonate-rich sedimentary rocks, which were probably assimilated by basaltic magma. The correlations between the contents of trace incompatible elements in rocks with SiO2 = 53–77 wt.% testify to the assimilation of crustal substrata by parental basaltic melts and the subsequent differentiation of contaminated magmas (AFC model). We propose a model for the formation of primary melts with the simultaneous participation of magmatic sources of two types: plume and fluid-saturated suprasubductional, localized beneath the active continental margin. 相似文献
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S.V. Andryushchenko A.A. Vorontsov V.V. Yarmolyuk I.V. Sandimirov 《Russian Geology and Geophysics》2010,51(7):734-749
The Khambin volcanotectonic complex is a horst framing the Late Cretaceous Lake Gusinoe basin in the northwest. This complex is due to the intracontinental rift conditions which existed in western Transbaikalia in the Late Mesozoic. They gave rise to a system of subparallel grabens and horsts in present-day topography. The magmatic evolution of this complex spans from 159 to 117 Ma and is divided into three stages. The first stage (159–156 Ma) witnessed the formation of thick (up to 1500 m) volcanic masses of trachybasalts, basaltic trachyandesites, trachytes, trachydacites, trachyrhyolites, and pantellerites. The next two stages were the formation of isolated ancient volcanoes (127–124 Ma) composed of trachybasalts, basaltic trachyandesites, phonotephrites, tephriphonolites, and alkali trachytes and the formation of the Murtoi (Lake Gusinoe) essexite dike (122–117 Ma). The main trends for igneous associations from early to late stages are reduced magmatism and reduced rock diversity because of the decreasing portion of felsic volcanic rocks. Mafic rocks show an increase in total alkalinity, the content of incompatible elements (Th, U, K, Rb, Pb, Nb, Ta, Zr, Hf), total REE content, and the LREE/HREE ratio. The Sr–Nd isotopic composition of these rocks remained nearly constant and corresponds to that of OIB-EMII mantle sources. Compositional variations are attributed to a time-dependent decrease in the degree of partial melting of a similar magma source. 相似文献
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The occurrence of infections with Trichinella sp. in polar bears (Ursus maritimus) from northeastern Greenland has been studied by examination of muscle samples, mainly diaphragm, from 38 animals shot during the period 1983-1987. Trichinella larvae were demonstrated in 12 bears (32%) with an average of 9.2 larvae/g muscle tissue. No bears younger than three years old were infected. The prevalence of Trichinella among bears of the age group 3-4 years was 25% and 53% among older animals. 相似文献
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