Cryptic crustal contamination of MORB primitive melts recorded in olivine-hosted glass and mineral inclusions     

Vadim S. Kamenetsky  Andrey A. Gurenko 《Contributions to Mineralogy and Petrology》2007,153(4):465-481

The origin of compositional heterogeneities among the magmas parental to mid-ocean ridge basalts (MORB) was investigated using a single rock piece of the olivine-phyric basalt from 43°N, Mid-Atlantic Ridge (AII D11-177). The exceptional feature of this sample is presence of very primitive olivine crystals (90–91 mol% Fo) that are significantly variable in terms of CaO (0.15–0.35 wt%). A population of low-Ca olivine (0.15–0.25 wt% CaO) is also notably distinct from high-Ca olivine population in AII D11-177, and primitive MORB olivine in general, in having unusual assemblage of trapped mineral and glass inclusions. Mineral inclusions are represented by high-magnesian (Mg# 90.7–91.1 mol%) orthopyroxene and Cr-spinel, distinctly enriched in TiO₂ (up to 5 wt%, c.f. <1 wt% in common MORB spinel). Glass inclusions associated with orthopyroxene and high-Ti Cr-spinel have andesitic compositions (53–58 wt% SiO₂). Compared to the pillow-rim glass and “normal” MORB inclusions, the Si-rich glass inclusions in low-Ca olivine have strongly reduced Ca and elevated concentrations of Ti, Na, K, P, Cl, and highly incompatible trace elements. Strong variability is recorded among glass inclusions within a single olivine phenocrysts. We argue that the observed compositional anomalies are mineralogically controlled, and thus may arise from the interaction between hot MORB magmas and crystal cumulates in the oceanic crust or magma chamber.  相似文献   

Interpretation of experimental data on HF propagation on the St. Petersburg-Spitsbergen path     

M. Yu. Andreev  D. V. Blagoveshchensky  V. M. Vystavnoi  V. S. Mingalev  G. I. Mingaleva 《Geomagnetism and Aeronomy》2007,47(4):502-509

The experimental ionograms of the oblique-incidence sounding of the ionosphere, obtained on the St. Petersburg-Spitsbergen high-latitude HF radio path during the magnetically quiet period December 14–15, 2001, are compared with the model calculations of radiowave trajectories. For this purpose, the corresponding oblique-incidence ionograms are numerically synthesized using the technique based on the shooting method and the computer program for constructing HF radiowave trajectories. The three-dimensional electron density distribution, calculated using the mathematical model of the high-latitude ionosphere previously developed at the Polar Geophysical Institute (PGI), is used to model radio propagation. The numerical calculations make it possible mainly to explain the specific features of the experimental data on the oblique-incidence sounding of the ionosphere.  相似文献   

The fauna of the Aral Sea in 1989. 2. The zooplankton     

N. I. Andreev  I. S. Plotnikov  N. V. Aladin 《International Journal of Salt Lake Research》1992,1(1):111-116

Data are presented on the composition and biomass of the Aral Sea zooplankton in August and October, 1989. As salinity gradually increased, a decrease in zooplankton species composition occurred at a salinity of 25–30 g L⁻¹. Because the Aral has now divided into two water-bodies, the zooplankton communities in these lakes have begun to conform with their individual hydrological and biological regimes.  相似文献   

Mitigating the Rate and Extent of Global Warming   总被引：1，自引：0，他引：1  

Stefan Rahmstorf  Andrey Ganopolski 《Climatic change》2002,52(3):255-262

Editorial Introduction

Mitigating the Rate and Extent of Global Warming  相似文献   

The outer scale of solar-wind turbulence from GALILEO coronal-sounding data     

A. I. Efimov  I. V. Chashei  L. N. Samoznaev  V. E. Andreev  M. K. Bird  P. Edenhofer  D. Plettemeier  R. Wohlmuth 《Astronomy Reports》2002,46(7):579-590

Radio sounding experiments on of the solar plasma were carried out by the GALILEO spacecraft using S-band (2295 MHz) signals in 1995–1996 a period of minimum solar activity. Equatorial regions at heliocentric distances of 7–80 solar radii were studied. The frequency of the received signal was detected by three ground stations. By carrying out continuous observations of unprecedented duration and processing the data using spectral and correlation methods, we have obtained reliable information on large-scale inhomogeneities of the solar-wind density for the first time. The outer turbulence scale increases with heliocentric distance, the dependence being close to linear. We estimate the outer turbulence scale and analyze its dependence on distance from the Sun and local plasma parameters for a model in which the outer scale is formed due to competition between the linear amplification of Alfven waves in the irregular, moving solar-wind plasma and the nonlinear transfer of turbulent energy to higher frequencies. A comparison of predictions for various specific cases of this model with the observational data suggests that the main nonlinear processes responsible for the formation of the inertial range of the spectrum on the investigated scales are three-wave decay processes involving Alfven and magnetoacoustic waves.  相似文献   

Seismogenic destruction of the Kamenka medieval fortress, northern Issyk-Kul region, Tien Shan (Kyrgyzstan)     

Andrey M. Korjenkov  J. Ramon Arrowsmith  Christopher Crosby  Ernes Mamyrov  Lyubov A. Orlova  Irina E. Povolotskaya  Kubatbek Tabaldiev 《Journal of Seismology》2006,10(4):431-442

A paleoseismological study of the medieval Kamenka fortress in the northern part of the Issyk-Kul Lake depression, northern Tien Shan in Kyrgyzstan, revealed an oblique slip thrust fault scarp offsetting the fortification walls. This 700 m long scarp is not related to the 1911 Kebin Earthquake (Ms 8.2) fault scarps which are widespread in the region. As analysis of stratigraphy in a paleoseismic trench and archaeological evidence reveal, it can be assigned to a major twelfth century a.d. earthquake which produced up to 4 m of oblique slip thrusting antithetic to that of the nearby dominant faults. The inferred surface rupturing earthquake apparently caused the fortress destruction and was likely the primary reason for its abandonment, not the Mongolian–Tatar invasions as previously thought.  相似文献   

Model study of the effect of the main ionospheric trough on oblique HF radiowave propagation     

M. Yu. Andreev  T. N. Lukicheva  V. S. Mingalev 《Geomagnetism and Aeronomy》2006,46(1):94-100

The purpose of this paper is to study the effect of the main ionospheric trough location on the form of oblique sounding ionograms on the Murmansk-St. Petersburg subauroral radio path. Using a mathematical model of the high-latitude ionosphere, we have calculated four different distributions of electron density along the radio path. One of the distributions has been obtained when the trough is absent, and the remaining three distributions contain troughs of approximately identical depth and width but located at different distances from the ends of the radio path. Using the program of two-dimensional ray tracing, we numerically synthesized oblique-incidence ionograms for each of the four obtained distributions of electron density. The calculations have shown that the location of the main ionospheric trough affects considerably the shape of oblique-incidence ionograms.  相似文献   

Plio-Pleistocene geological record and small mammal faunas, eastern shore of the Azov Sea, Southern European Russia   总被引：1，自引：0，他引：1  

Alexey S. Tesakov  Andrey E. Dodonov  Vadim V. Titov  Valery M. Trubikhin 《Quaternary International》2007,160(1):57

The shoreline of the Taganrog Gulf of the Azov Sea at the mouth of Don River provides a series of extended Upper Pliocene and Quaternary sections that have been actively studied in the last century. This extraglacial region had a complex sedimentary history combining subaerial aggradation with marine, fluvial, and deltaic sedimentation. The well-exposed stratigraphical sequence and abundant palaeontological record continuously attract geologists and highlight the region as one of international importance for the addressing of numerous problems of Late Pliocene and Quaternary stratigraphy and palaeogeography. Fossil mammalian faunas of the region include important Eurasian biostratigraphical markers such as Stenocranius ex gr. hintoni-gregaloides, Lagurini spp., and Mimomys savini. For many years, fossil remains of mammals provide decisive clues to the geological history of the region. Recent geological studies of reference sections have provided data on small mammals, palaeomagnetism and palaeogeographical reconstructions in the northeastern part of the Azovian Region. Mammalian assemblages indicate the presence of the Late Pliocene, late Early Pleistocene, Middle Pleistocene and Late Pleistocene levels and, in addition, provide a clear biostratigraphical context for the Early Middle Pleistocene transition.  相似文献   

Tilt Angles of Solar Filaments over the Period of 1919 – 2014     

Andrey G. Tlatov  Kirill M. Kuzanyan  Valeria V. Vasil’yeva 《Solar physics》2016,291(4):1115-1127

  相似文献   

Slow-Mode MHD Wave Penetration into a Coronal Null Point due to the Mode Transmission     

Andrey N. Afanasyev  Arkadiy M. Uralov 《Solar physics》2016,291(11):3185-3193

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