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Yu. A. Bogdanov A. Yu. Lein A. M. Sagalevich A. A. Ul’yanov S. A. Dorofeev N. V. Ul’yanova 《Geochemistry International》2006,44(4):403-418
Several hydrothermal sulfide structures were sampled using Mir manned submersibles in the relatively shallow Lucky Strike vent field, Mid-Atlantic Ridge; the bathymetric position of these structures varies by approximately 100 m. The investigation of the chemical and mineral compositions of hydrothermal ore occurrences led to the conclusion that the initial high-temperature ore-bearing solution ascending toward the surface became unstable and experienced phase separation beneath the ocean floor. The phase separation was responsible for the bathymetric control of hydrothermal ore formation in the ocean. 相似文献
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S. V. Shestov S. V. Kuzin A. M. Urnov A. S. Ul’yanov S. A. Bogachev 《Astronomy Letters》2010,36(1):44-58
Plasma temperature diagnostics in solar flares and active regions has been carried out using data from the SPIRIT spectroheliograph onboard the CORONAS-F satellite. The temperature distribution of the differential emission measure (DEM) has been determined from the relative intensities of spectral lines recorded in the spectral range 280–330 Å in the period from 2001 to 2005. Analysis of these distributions has led to the conclusion about the existence of active regions with various “characteristic” temperature compositions. The presence of a hot plasma with temperatures logT = 6.8?7.2 in active regions has been established for the first time from XUV spectroscopic data and monochromatic X-ray line images. The DEM distribution for intense long-decay flares has also been obtained for the first time and a similarity of the temperature compositions for flares of different classes at the decay phase has been found. The spectra have been modeled on the basis of the calculated DEMs. The systematic discrepancies between the calculated and measured line intensities are discussed. 相似文献
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The Chaman left‐lateral strike‐slip fault bounds the rigid Indian plate boundary at the western end of the Himalayan‐Tibetan orogen and is marked by contrasting topographic relief. Deformed landforms along the fault provide an excellent record for understanding this actively evolving intra‐continental strike‐slip fault. The geomorphic response of an active transpessional stretch of the Chaman fault was studied using digital elevation model (DEM) data integrated with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Visible and Near Infrared/Short Wave Infrared (VNIR/SWIR) and images from GeoEye‐1. Geologic and geomorphic mapping helped in reconstructing the Late Quaternary landscape history of this transpessional strand of the Chaman strike‐slip fault and the associated Spinatizha thrust fault in western Pakistan. Topographic analysis of a part of the transpression (the thrust bounded Roghani ridge) revealed northward growth of the Spinatizha fault with the presence of three water gaps and two corresponding wind gaps. Geomorphic indices including stream length‐gradient index, mountain front sinuosity, valley floor width to valley height ratios, and entrenchment of recent alluvial fan deposits were used to define the lateral growth and direction of propagation of the Spinatizha fault. Left‐lateral displacement along Chaman fault and uplift along the Spinatizha fault was defined using topographic analysis of the Roghani ridge and geomorphic mapping of an impressive alluvial fan, the Bostankaul fan. The landforms and structures record slip partitioning along the Indian plate boundary, and account for the convergence resulting from the difference in the Chaman fault azimuth and orientation of the velocity vector of the Indian plate. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Uniaxial compression of poorly lithified rocks leads to the formation of thin incompact layers (or bands, in the two-dimensional
case) parallel to the compression axis, which are characterized by increased porosity. The standard model of the formation
of such bands, as well as deformation bands of other types, associates them with the narrow zones of localization of plastic
deformations. In the case of decompaction, it is assumed that transverse tensile deformations are localized within the band,
which cause the band to dilate. Here, the formation of a band of localized deformations is treated as a loss-of-stability
phenomenon. Based on observations, we propose a fundamentally different model of incompact bands formation, according to which
the microdefects in sediment packing (pores) rather than the deformations are localized in the narrow zones. The localization
of pores, which are initially randomly distributed in the medium, occurs as a result of their migration through the geomaterial.
The migration and subsequent localization of pores are driven by a common mechanism, namely, a trend of a system to lower
its total energy (small variations in total energy are equal to the increment of free energy minus the work of external forces).
Migration of a single pore in a granular sedimentary rock is caused by the force f driving the defect. This force was introduced by J. Eshelby (1951; 1970). An important feature of our model is that the formation
of an incompact band here does not have a sense of a loss of stability. Quite the contrary, the formation of incompact bands
is treated as a gradual process spread over time. In this context, the origination of incompact band systems directly follows
from our model itself, without any a priori assumptions postulating the existence of such systems and without any special
tuning of the model parameters. Moreover, based on the proposed model, we can predict the incompact bands to always occur
in the form of systems rather than as individual structures. A single incompact band may only be formed when the force resisting
the pore motion, f
c
, is absent. 相似文献
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Authigenic carbonates in methane seeps from the Norwegian sea: Mineralogy, geochemistry, and genesis
A. Yu. Lein A. I. Gorshkov N. V. Pimenov Yu. A. Bogdanov P. Vogt O. Yu. Bogdanova V. M. Kuptsov N. V. Ul’yanova A. M. Sagalevich M. V. Ivanov 《Lithology and Mineral Resources》2000,35(4):295-310
Authigenic carbonates in the caldera of an Arctic (72°N) submarine mud volcano with active CH4bearing fluid discharge are formed at the bottom surface during anaerobic microbial methane oxidation. The microbial community
consists of specific methane-producing bacteria, which act as methanetrophic ones in conditions of excess methane, and sulfate
reducers developing on hydrogen, which is an intermediate product of microbial CH4 oxidation. Isotopically light carbon (δ13Cav =−28.9%0) of carbon dioxide produced during CH4 oxidation is the main carbonate carbon source. Heavy oxygen isotope ratio (δ18Oav = 5%0) in carbonates is inherited from seawater sulfate. A rapid sulfate reduction (up to 12 mg S dm−3 day−1) results in total exhausting of sulfate ion in the upper sediment layer (10 cm). Because of this, carbonates can only be
formed in surface sediments near the water-bottom interface. Authigenic carbonates occurring within sediments occur do notin situ. Salinity, as well as CO
3
2−
/Ca and Mg/Ca ratios, correspond to the field of nonmagnesian calcium carbonate precipitation. Calcite is the dominant carbonate
mineral in the methane seep caldera, where it occurs in the paragenetic association with barite. The radiocarbon age of carbonates
is about 10000 yr. 相似文献
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M. V. Popov A. D. Kuz’min O. M. Ul’yanov A. A. Deshpande A. A. Ershov V. V. Zakharenko V. I. Kondrat’ev S. V. Kostyuk B. Ya. Losovskiĭ V. A. Soglasnov 《Astronomy Reports》2006,50(7):562-568
The results of simultaneous multifrequency observations of giant radio pulses from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses detected at 111 MHz, 21 were identified with counterparts observed simultaneously at 600 MHz. The spectral indices for the power-law frequency dependence of the giant-pulse energies are from ?3.1 to ?1.6. The mean spectral index is ?2.7 ± 0.1 and is the same for both frequency combinations (600–111 MHz and 600–23 MHz). The large scatter in the spectral indices of the individual pulses and the large number of unidentified giant pulses suggest that the spectra of the individual giant pulses do not actually follow a simple power law. The observed shapes of the giant pulses at all three frequencies are determined by scattering on interstellar plasma inhomogeneities. The scatter-broadening of the pulses and its frequency dependence were determined as τ sc = 20(ν/100)?3.5±0.1 ms, where frequency ν is in MHz. 相似文献