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31.
The behavior of rare earth elements (REE) and Th is studied along the west–east transect at 22°N across the Atlantic Ocean. It is shown that both REE and Th contents, relative to Al (the most lithogenic element), increase toward the pelagic region. The increasing trend becomes more complicated due to variations in the content of biogenic carbonate that serves as a diluting component in sediments. The REE composition varies symmetrically relative to the Mid-Atlantic Ridge (MAR) emphasizing a weak hydrothermal influence on sediments of the ridge axis, although the well-known criteria for hydrothermal contribution, such as Al/(Al + Mn + Fe) and (Fe + Mn)/Ti, do not reach critical values. Variations in the REE content and composition allowed us to distinguish the following five sediment zones in the transect: (I) terrigenous sediments of the Nares abyssal plain; (II) pelagic sediments of the North American Basin; (III) carbonate ooze of the MAR axis; (IV) pelagic sediments of the Canary Basin; and (V) terrigenous clay and calcareous mud of the African continental slope and slope base. Ferromanganese nodules of the hydrogenetic type with extremely high Ce (up to 1801 ppm) and Th (up to 138 ppm) contents occur in pelagic sediments. It is ascertained that P, REE, and Th concentrations depend on Fe content in Atlantic sediments. Therefore, one can suggest that only a minor amount of phosphorus is bound in bone debris. The low concentration of bone debris phosphorus is a result of relatively high sedimentation rates in the Atlantic, as compared with those in pelagic regions of the Pacific. 相似文献
32.
Normal annual data are used to evaluate the within-year variations in the concentrations of biogenic substances (organic and mineral components of N and P, dissolved organic carbon, inorganic Si) in the major tributaries of the Caspian Sea. Variations in the concentrations of biogenic substances are analyzed, the relationships between their mass concentrations in individual months are evaluated, and correlation between the organic and mineral components of N and P and their aggregated fractions are established. The obtained high-significance correlation between the concentrations of N and P components suggests that the rates of biochemical processes of biogenic substance transformation taking place in the water of tributaries are commensurable. 相似文献
33.
I. Sandahl S. Barabash H. Borg E. Yu. Budnik E. M. Dubinin U. Eklund H. Johansson H. Koskinen K. Lundin R. Lundin A. Mostrom R. Pellinen N. F. Pissarenko T. Pulkkinen P. Toivanen A. V. Zakharov 《Annales Geophysicae》1997,15(5):542-552
PROMICS-3 is a plasma experiment flown in the Russian project Interball. It performs three-dimensional (3D) measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 12 eV–35 keV. The Interball project consists of two main satellites, the Tail Probe and the Auroral Probe, each with one subsatellite. The Interball Tail Probe was launched on 3 August 1995, into a 65° inclination orbit with apogee at about 30 RE. Both main satellites carry identical PROMICS-3 instruments and thus direct comparisons of the particle distributions will be possible once the Auroral Probe is launched. Furthermore, PROMICS-3-Tail is the first instrument measuring the 3D ion distribution function in the magnetospheric boundary layers at high latitudes. In this paper we describe the PROMICS-3 instrument and show initial results from the Tail probe, measurements of the mag-netosheath, plasma sheet, and ring current plasmas. 相似文献
34.
Fluctuations of the electric and magnetic field are studied in collisionless shock formed during plasma flow over a terrella. Spectra of magnetic fluctuations in the laboratory experiment and in space appear to coincide in dimensionless units. Electric field fluctuations appear at the shock wave formation, with frequencies in the hybrid Larmor frequency range. The appearance of noise is preceeded by the formation of positive potential maxima. The reflection of ions from the potential maxima must lead to two stream motion in a plasma with magnetized electrons. Such motion is unstable and excites longitudinal waves. Dissipation of energy of the directional motion after damping of electrical noises apparently occurs only through microfluctuations of the magnetic field. 相似文献
35.
I. M. Podgorny E. M. Dubinin Yu. N. Potanin S. I. Shkolnikova 《Astrophysics and Space Science》1979,61(2):369-374
In order to simulate a cometary tail in a laboratory the flow of hydrogen collisionless supersonic plasma with the magnetic field frozen in was used. The wax ball served as a model of the cometary nucleus. The experimental conditions met the principle of limiting simulation. Field lines enveloped the nucleus at the day side and stretched along the flow at the night side. Tension of field lines in the magnetic tail provided the acceleration of ionized products of wax evaporation up to about 106 cm s–1. The control experiments showed that the magnetic tail is caused by currents due to the Lorentz electric field. 相似文献
36.
A. A. Chibilev D. V. Veselkin N. B. Kuyantseva O. E. Chashchina A. E. Dubinin 《Doklady Earth Sciences》2016,468(2):619-622
This paper considers the impact of climatic factors on the forest fire rate in Ilmen State Reserve based on 66 years of direct observation data for 1948–2013. This period was marked by a gradual annual increase in the number of recorded fires in the reserve. The higher fire rate is generally related to lengthening of the fire season and more frequent fires in the spring and summer–early autumn periods. We did not obtain sufficient evidence to verify a relation of the higher fire rate to climate changes. The average monthly and seasonal weather conditions can be involved to explain only some causes of the interannual fire rate variability. The observed changes in some climatic characteristics could have contributed to an increase in the fire rate, while others could have reduced it. 相似文献
37.
I. Sandahl S. Barabash H. Borg E. Y. Budnik E. M. Dubinin U. Eklund H. Koskinen K. Lundin R. Lundin A. Mälkki R. Pellinen N. F. Pissarenko T. Pulkkinen A. V. Zakharov 《Annales Geophysicae》1999,17(5):659-673
The PROMICS-3 instrument on Interball-2 is nominally identical to the PROMICS-3 instrument on Interball-1. It performs three-dimensional measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 300 eV–35 keV. Interball-2 was launched on August 29, 1996, into an orbit with the same inclination as that of Interball-1, 63°, but with apogee at 20 000 km. In this study the PROMICS-3 instrument on Interball-2 is briefly described and examples of the first results are presented. Firstly, we report observations of upward moving molecular ions with energies of up to 700 eV at the poleward edge of the auroral oval. Previous observations of outflowing molecular ions have been at lower altitudes and lower energies. Secondly, we show observations of dawnside magnetosheath plasma injections. Using conjugate data from both PROMICS-3 instruments we have found dispersion structures above the morningside auroral oval, which occurred simultaneously with isolated “pockets” of magnetosheath plasma at a distance of XGSM = −14 to −12 RE, which had been injected into the inner part of the low-latitude boundary layer. These isolated plasma structures were sites of strong field-aligned currents and are proposed to be the magnetospheric counterparts of the dispersion structures. 相似文献
38.
Geochemistry of rare earth elements in micro-and macronodules from the pacific bioproductive zone 总被引:1,自引:0,他引:1
Concentrations and compositions of rare earth elements (REE) in three micronodule fractions (50–250, 250–500, and >500 μm),
coexisting macronodules, and host sediments are examined. The samples were collected from three sites (Guatemala Basin, Peru
Basin, and northern equatorial Pacific) located in elevated bioproductivity zones of the surficial water. The influence of
micronodule size is dominant for REE compositions and subordinate for REE concentrations. For example, the Ce concentration
inversely correlates with the micronodule fraction dimension and drops to the lowest value in macronodules and host sediments.
The Ce decrease is generally accompanied by the Mn/Fe increase in micro- and macronodules. Hence, the role of diagenetic source
of material directly correlates with the micronodule dimension. The contribution of diagenetic source is maximal for macronodules.
The REE signature distinctions of micronodules and macronodules can be attributed to variations of hydrogenic iron oxyhydroxides
and diagenetic (hydrothermal) iron hydroxophosphates that are the major REE carriers in ferromanganese ore deposits. The relationship
and general trend in the chemistry of coexisting macronodules suggest that they can represent products of the initial stage
of nodule formation. 相似文献
39.
Geotectonics - This study focuses on physical modeling of interaction between the Indian and Pacific spreading axes, which resulted in separation of the Tasmania and Adélie blocks during the... 相似文献
40.
A. L. Grokholskii Ye. P. Dubinin I. V. Shapovalova 《Moscow University Geology Bulletin》2010,65(3):185-193
The results of experimental modeling and features of structure formation in the zones of nontrans-form offsets (NTOs) of spreading
axes are presented. The experiments were performed on materials that are colloidal systems based on liquid and solid hydrocarbons,
taking into account the similarity of conditions. The following parameters were changed during the experiments: (1) the thickness
of the model lithosphere of the rift zone, (2) the thickness of the lithosphere in the zone of nontransform offsets between
the rift segments; (3) the spreading velocity. The critical values of offsets for the spreading axes at which a character
of structure formation in the zones of NTOs is changed were established. 相似文献