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921.
The chemical compositions of the atmospheres of six metal-poor stars are analyzed. Spectra with signal-to-noise ratios of no less than 100 and a resolution of R≈17 000 were obtained using the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The abundances of Li, O, α-process elements (Mg, Si, Ca, Ti), Na, K, Sc, iron-peak elements (Cr, Mn, Fe, Ni, Cu, Zn), and s-process elements (Y, Ba) are derived. The star G251-54 ([Fe/H]=?1.55, T eff=5541 K, logg=3.58) is deficient in some elements compared to both stars with similar metallicities and the Sun. The atmosphere of G251-54 has the following elemental abundances relative to iron: [O/Fe]=+0.47, [α/Fe]≈?0.3, [Na/Fe]=?0.60, [Sc/Fe]=?0.57, [Cr, Ni, Fe]≈0, [Zn/Fe]=+0.16, [Cu/Fe]=?0.66, [Y/Fe]=?0.70, and [Ba/Fe]=?1.35. The remaining five stars have metallicities in the range ?1.6<[Fe/H]1.3 and normal abundances for this metallicity interval and are used as reference stars for comparison with the chemical composition of G251-54. Possible explanations for deviations of the abundances of some elements from the mean relations established for halo objects are discussed. 相似文献
922.
A. V. Maslov 《Lithology and Mineral Resources》2002,37(5):462-474
Large-scale facies associations typical of intra- and pericratonic Riphean sections of the Volga–Ural region, western slope of the Urals, Timan–Pechora region, Kola Peninsula, outer and inner parts of the Siberian, North American, and Indian platforms are considered. The reconstruction of their lateral and vertical relationships makes it possible to reconstruct principal trends in the evolution of late Precambrian sedimentary basins. Recommended special studies aimed at the restoration of spatial architecture of associations retained in fragments of Riphean sedimentary basins could yield a substantially new information on the basin filling. Such approach has important implications for estimation of the potential of late Precambrian sedimentary basins with respect to the exploration for mineral resources including hydrocarbons. 相似文献
923.
Krupskaya V. V. Andreeva I. A. Sergeeva E. I. Cherkashev G. A. 《Lithology and Mineral Resources》2002,37(2):130-137
The submarine Haakon Mosby mud volcano was studied in detail during several cruises, resulting in the collection of an abundant and diverse lithological material. Comprehensive field and laboratory studies made it possible to identify different types of sediments with specific granulometric and pelite fraction (<0.005 mm) compositions, as well as the regularity of their spatial distribution relative to various morphostructural zones of the mud volcano. 相似文献
924.
Seismic Hazard for Selected Sites in Greece: A Bayesian Estimate of Seismic Peak Ground Acceleration 总被引:1,自引:1,他引:1
A procedure for estimating maximum values of seismic peak ground accelerationat the examined site and quantiles of its probabilistic distribution in a future timeinterval of a given length is considered. The input information for the method areseismic catalog and regression relation between peak seismic acceleration at a givenpoint and magnitude and distance from the site to epicenter (seismic attenuation law).The method is based on Bayesian approach, which simply accounts for influenceof uncertainties of seismic acceleration values. The main assumptions for the method are Poissonian character of seismic events flow and distribution law of Gutenberg-Richter's type. The method is applied to seismic hazard estimation in six selected sitesin Greece. 相似文献
925.
Lithology and Mineral Resources - The chemical composition and Nd isotope systematics were obtained for mudrocks (mudstones) from sections of the Siberian hypostratotype of the Riphean and Vendian... 相似文献
926.
V. M. Tereshchenko 《Astronomy Reports》2002,46(3):224-232
We have obtained spectral energy distributions for 41 7m–8m stars near the celestial equator (δ=±3°). The λλ3100–7600 Å spectral range is studied with a spectral resolution of 50 Å. The relative rms error in the visible is 1–2%, increasing to 3–5% towards the edges of the wavelength interval studied. All stars are referenced to a single standard, the circumpolar star HD 221525. The synthetic colors of common stars are compared with those observed in four photometric systems: U BV, W BV R, uvby, and that of the TYCHO catalog. The program stars are recommended as secondary spectrophotometric standards. 相似文献
927.
A comprehensive lithological–geochemical study of Neopleistocene–Holocene sediments from Russian Arctic showed that these sediments formed in rather similar sedimentation conditions, which were common for polar lithogenesis. This is reflected in the lithology of bottom sediments and their relatively close compositions. 相似文献
928.
The Cone-in-Cone Structure and Its Origin 总被引:1,自引:0,他引:1
Morphostructural investigation of carbonate cone-in-cone formations allows to conclude that they belong to self-organizing (dissipative, according to I. Prigogine's terminology) systems of the geological past formed in a thermogradient field at the expense of energy of heat and mass transfer (Prigogine and Stengers, 1984). First, the fluid-convective metasomatic hypothesis unites and reconciles the most well-known hypotheses that previously seemed to be incompatible and transforms them to rather consistent particular cases of a more intricate multistage geological phenomenon. Second, it helps to identify the morphologically and genetically analogous noncarbonate structures that mimic biogenic ones. The probable indicative role of cone-in-cone structure in the mapping of fluid-conducting systems is a consequence of the proposed hypothesis. 相似文献
929.
V. I. Vinogradov M. I. Bujakaite V. I. Murav'ev M. B. Burzin A. F. Veis 《Lithology and Mineral Resources》2002,37(5):454-461
The Rb–Sr characteristics of whole-rock samples of Upper Vendian clayey rocks recovered by Gavrilov-Yam boreholes are studied. The Rb–Sr age versus sampling depth relationship has been revealed. Three sample assemblages are identified. The errorchron relationship of samples in the first interval (1760–2400 m) fits the age of 390 ± 40 Ma corresponding to the initial Hercynian history characterized by the transformation of platformal sediments. The other two assemblages (2410–2525 and 2528–2560 m) make up isochrons with slopes corresponding to 590 ± 50 and 690 ± 10 Ma, respectively. Their geochronological meaning is unclear. 相似文献
930.
The application of variations in the earth's gravity in groundwater exploration on a regional scale, especially in sedimentary
basins, metamorphic terrains, valley fills, and for buried alluvial channels, is well established. However, its use in hard
crystalline rocks is little known. In granite, for example, the upper weathered layer is a potential primary aquifer, and
the underlying fractured rock can form a secondary aquifer. Fracturing and weathering increases the porosity of a rock, thereby
reducing the bulk density. Changes in gravity anomalies of 0.1–0.7 mGal for granites, due to weathering or variations in lithology,
can be detected.
To test the use of gravity as a groundwater exploration tool for crystalline rocks, a gravity survey of the peninsular shield
granites underlying Osmania University Campus, Hyderabad, India, was undertaken. At the site, gravity anomalies reflect variations
in the lithology and in the thickness of weathered zones. These anomalies also define the position of intrusives and lineaments.
Areas of more deeply weathered granite that contain wells of higher groundwater yield are represented by negative gravity
values. In the weathered zone, well yield has an inverse relation to the magnitudes of residual gravity. The study confirms
the feasibility of gravity as a tool for groundwater exploration in crystalline rocks.
Electronic Publication 相似文献