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991.
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
992.
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
993.
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
994.
José F. Noguera Lluís Rivero Xavier Font Andrés Navarro Francisco Martínez 《Environmental Geology》2002,41(8):898-905
995.
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
996.
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
997.
998.
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
999.
V. M. Danilov 《Astronomy Reports》2002,46(6):443-450
Models of open clusters in a state of equilibrium in the space of the three parameters of the stellar motion and simultaneously far from virial equilibrium are analyzed. A formula for the phase-space stellar number density in such cluster models is derived, as well as formulas for the integrated and differential energy distributions of the phase-space volume occupied by cluster stars per unit stellar mass. These three quantities are computed for several times exceeding the time for violent relaxation of the cluster model. The phase-space density function obtained is used to compute the distribution of the absolute values of stellar velocities for the cluster model considered. 相似文献
1000.
D. V. Bisikalo A. A. Boyarchuk E. Yu. Kilpio O. A. Kuznetsov 《Astronomy Reports》2002,46(12):1022-1029
A new mechanism is proposed to account for transitions between the quiescent and active states of symbiotic stars. A numerical study of the gas dynamics of the flows in the symbiotic star Z And shows that even small variations in the velocity of the wind from the cool giant can abruptly change the flow structure near the hot component. Such changes alter the accretion regime as the wind velocity increases: disk accretion makes a transition to accretion from the flow. Our calculations indicate that the accretion rate increases by a factor of several tens over a short time interval (~0.1 of the orbital period) during the rearrangement of the flow, when the accretion disk is destroyed. 相似文献