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M. V. Goroshko B. F. Shevchenko V. A. Guryanov G. Z. Gil’manova 《Russian Journal of Pacific Geology》2016,10(1):13-27
The tectonics and metallogeny of the junction zone between the North Asian craton and Pacific tectonic belt are considered. This zone is characterized by a wide variety of structures superposed on the metamorphic basement, which was formed in the course of a multistage geologic development of the craton from the Precambrian to the Cenozoic. They are related to the craton evolution and its response to the collision and subduction processes in the adjacent orogenic belt, processes in the passive and active continental margins, and plume magmatism. The geological structure of the region includes blocks of metamorphic rocks of the Aldan–Stanovoi shield, Paleoproterozoic volcanogenic troughs, Mesoproterozoic–Neoproterozoic and Early Paleozoic structures of the platform cover, Late Paleozoic volcanic and terrigenous troughs, structures of the Late Mesozoic Okhotsk–Chukotka volcanic belt of the active continental margin, and Late Cretaceous riftogenic structures formed in response to plume magmatism. In total, six metallogenic epochs are recognized in the development of ore mineralization: Archean–Early Paleoproterozoic, Late Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Late Paleozoic, and Late Mesozoic. The minerageny of the junction zone between the craton and Pacific belt is highly diversified, being characterized by distinct evolution in time and space. Each development stage features its own set of mineral resources. 相似文献
3.
Calcareous nannoplankton from sediment trap samples collected at six sites in the Atlantic Ocean from 23° S to 73° N (cruise 20 of R/V Vityaz’ and cruise 33 and 34 of R/V Akademik Mstislav Keldysh). Those samples were studied with a scanning electron microscope. In the coastal and open-sea regions of the North and South Atlantic and in the subarctic region of the Norwegian Sea, the conditions are significantly different. In the shelf area of the Benguela upwelling, 11 species were recognized; some of them were agglutinated by diatoms and tintinnides or covered the surface of pellets. The Broken Spur and TAG pelagic areas of the North Atlantic contained up to 43 coccolith species. They included holococcoliths, large pelagic, and delicate easily soluble species distributed over the entire water column. The presence of coccoliths in the high-latitude area of the Norwegian Sea is related to their supply with the warmer North Atlantic waters. These assemblages are distinguished by a low species diversity and an enhancement of the coccolith solubility with the depth increase. 相似文献
4.
We consider the problem of calculating the Lyapunov time (the characteristic time of predictable dynamics) of chaotic motion in the vicinity of separatrices of orbital resonances in satellite systems. The primary objects of study are the chaotic regimes that have occurred in the history of the orbital dynamics of the second and fifth Uranian satellites (Umbriel and Miranda) and the first and third Saturnian satellites (Mimas and Tethys). We study the dynamics in the vicinity of separatrices of the resonance multiplets corresponding to the 3 : 1 commensurability of mean motions of Miranda and Umbriel and the multiplets corresponding to the 2 : 1 commensurability of mean motions of Mimas and Tethys. These chaotic regimes have most probably contributed much to the long-term orbital evolution of the two satellite systems. The equations of motion have been numerically integrated to estimate the Lyapunov time in models corresponding to various epochs of the system evolution. Analytical estimates of the Lyapunov time have been obtained by a method (Shevchenko, 2002) based on the separatrix map theory. The analytical estimates have been compared to estimates obtained by direct numerical integration.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 4, 2005, pp. 364–374.Original Russian Text Copyright © 2005 by Mel’nikov, Shevchenko. 相似文献
5.
I.N. Belskaya Yu.G. Shkuratov N.M. Shakhovskoy A. Cellino A.A. Ovcharenko V.G. Shevchenko C. Barbieri 《Icarus》2005,178(1):213-221
UBVRI polarimetric observations carried out in 1997-2004 for the F-type Asteroids 302 Clarissa, 419 Aurelia, 704 Interamnia, and 762 Pulcova (V band only) are presented. Asteroid 419 Aurelia is characterized by a negative polarization branch which is unusual for low-albedo asteroids. Its depth is about 1%, while the inversion angle, close to 14°, reaches the smallest value ever observed for asteroids. This is the first definite example of a minor body exhibiting a considerable decrease of both the depth and width of the negative polarization branch in comparison with polarization properties of other low-albedo bodies, mimicking a behavior previously found in laboratory measurements of extremely dark surfaces. The F-type Asteroids 302 Clarissa and 704 Interamnia are also characterized by unusually small inversion angles compared to other asteroid types, while Asteroid 762 Pulcova seems to have an ordinary negative polarization branch. Laboratory measurements of low-albedo samples and computer simulations of light scattering by particles of irregular shapes were made to interpret observational data. We find that an optical homogeneity of regolith microstructure at scales of the order of visible light wavelengths may be responsible for relatively small values of the depth of the negative polarization branch and of the inversion angle. Peculiar features of the F-type asteroids compared to other taxonomic classes are discussed. 相似文献
6.
Irina N Belskaya Vasilij G Shevchenko Yurij N Krugly Yurij S Efimov Alberto Cellino 《Icarus》2003,166(2):276-284
The first results of the observational program devoted to simultaneous investigation of asteroid polarimetric and photometric opposition phenomena are presented. UBVRI polarimetric and V-band photometric observations of the S-type Asteroid 20 Massalia and the E-type Asteroids 214 Aschera and 620 Drakonia were carried out in 1996-1999 down to phase angles of 0.08°, 0.7°, and 1.2°, correspondingly. The S-type Asteroid 20 Massalia is characterized by the pronounced brightness opposition surge with an amplitude larger than that observed for the E-type asteroids. A sharp peak of negative polarization at small phase angles was not observed for this asteroid. The value of polarization degree at phase angle α<1° is less than 0.5% for both S and E types. The negative polarization branches of S and especially E-asteroids have an asymmetrical shape. The phase angle at which the polarization minimum occurs is close to the angle at which non-linear increase begins in the asteroid magnitude phase curves. A relation of the observed effects to the mechanism of coherent backscattering is discussed. 相似文献
7.
Possible rotation states of two satellites of Saturn, Prometheus (S16) and Pandora (S17), are studied by means of numerical experiments. The attitude stability of all possible modes of synchronous rotation and the motion close to these modes is analyzed by means of computation of the Lyapunov spectra of the motion. The stability analysis confirms that the rotation of Prometheus and Pandora might be chaotic, though the possibility of regular behaviour is not excluded. For the both satellites, the attitude instability zones form series of concentric belts enclosing the main synchronous resonance center in the phase space sections. A hypothesis is put forward that these belts might form “barriers” for capturing the satellites in synchronous rotation. The satellites in chaotic rotation can mimic ordinary regular synchronous behaviour: they preserve preferred orientation for long periods of time, the largest axis of satellite’s figure being directed approximately towards Saturn. 相似文献
8.
Ye. I. Polyakova Ye. A. Novichkova A. P. Lisitzin V. P. Shevchenko M. D. Kravchishina 《Oceanology》2016,56(2):289-300
Diatom algae, aquatic palynomorphs, and the grain-size of surface sediments from bays of the White Sea were investigated in a program dedicated to the study of marginal filters (MF) in the Severnaya Dvina, Onega, and Kem rivers. Three microalgal assemblages are established in surface sediments, which replace each other successively with distance from river mouths and are characterized by a gradual decrease in a share of freshwater species of diatoms and Chlorophyceae algae, significantly varying concentrations of marine diatoms and dinocysts due to changes in water salinity, grain-size composition of sediments, quantitative distribution of suspended particulate matter (SPM), and water productivity at different marginal filter stages. 相似文献
9.
S. F. Vinokurov A. G. Gurbanov O. A. Bogatikov V. A. Sychkova A. V. Shevchenko A. B. Lexin Z. I. Dudarov 《Doklady Earth Sciences》2016,470(2):1034-1036
The decontamination of buried wastes of the Tyrnyauz Tungsten–Molybdenum Plant is complicated by the geochemical features of the waste composition: low sulfide and high carbonate content, polyelemental composition, and considerable amounts of technogenic admixtures (kerosene, oils, soda, and soluble glasses). These circumstances result in sufficient complication of the suggested technology of waste treatment, including the sulfuric-acid leaching and separate sorption recovery of hazardous and useful elements from the working solution. 相似文献
10.
Novigatsky A. N. Lisitzin A. P. Shevchenko V. P. Klyuvitkin A. A. Kravchishina M. D. Politova N. V. 《Oceanology》2020,60(3):372-383
Oceanology - A new approach has been applied to studying marine sedimentation using dispersed sedimentary material in sediment traps compared to the surface layer of bottom sediments. Based on... 相似文献