Reconstruction of the metamorphic <Emphasis Type="Italic">P–T</Emphasis> path from the garnet zoning in aluminous schists from the Tsogt Block,Mongolian Altai     

V. P. Sukhorukov  O. P. Polyansky  A. A. Krylov  S. V. Zinoviev 《Petrology》2016,24(4):409-432

The paper presents original authors’ data on aluminous schists in the Tsogt tectonic plate in the Southern Altai Metamorphic Belt. The nappe includes a medium-temperature/medium-pressure zonal metamorphic complex, whose metamorphic grade varies from the greenschist to epidote-amphibolite facies. The garnet and garnet–staurolite schists contain three garnet generations of different composition and morphology. The P–T metamorphic parameters estimated by mineralogical geothermometers and geobarometers and by numerical modeling with the PERPLEX 668 software provide evidence of two successive metamorphic episodes: high-gradient (of the andalusite–sillimanite type, geothermal gradient approximately 40–50°/km) and low-gradient (kyanite–sillimanite type, geothermal gradient approximately 27°/km). The P-T parameters of the older episode are T = 545–575°C and P = 3.1–3.7 kbar. Metamorphism during the younger episode was zonal, and its peak parameters were T = 560–565°C, P = 6.4–7.2 kbar for the garnet zone and T = 585–615°C, P = 7.1–7.8 kbar for the staurolite zone. The metamorphism evolved according to a clockwise P–T path: the pressure increased during the first episode at a practically constant temperature, and then during the second episode, the temperature increased at a nearly constant pressure. Such trends are typical of metamorphism related to collisional tectonic settings and may be explained by crustal thickening due to overthrusting. The regional crustal thickening reached at least 15–18 km.  相似文献   

Optimum trajectories for spacecraft mission to asteroid Apophis with a return to the Earth     

V. V. Ivashkin  I. V. Krylov  A. Lan 《Solar System Research》2013,47(4):334-345

A topical task for astronautics is to prepare a mission to the asteroid Apophis that is approaching the Earth. Determination of energetically favorable trajectories for a spacecraft involved in this mission with a return to the Earth has been considered. Two possible variants of engines for this mission are analyzed. The first variant employs electric engines with low jet thrust, while the second variant employs a spacecraft accelerated and controlled by only high-thrust engines. It is shown that both variants can be used in the mission to Apophis, but the use of electric engines with low thrust allows the project characteristics to be significantly improved.  相似文献   

Paleomagnetism of Cretaceous units of the Mametchinskiy Peninsula, Kuyul Region, Northeastern Russia: implications for development and evolution of the Northwest Pacific Basin     

William Harbert  Maxim Alexutin  Sergei Sokolov  Kirill Krylov  Vladimir Grigoriev  Alexander Heiphetz  Robert Graham 《Tectonophysics》2001,340(3-4):215-231

The northernmost part of the Kamchatka Peninsula of northeastern Russia, located along the northwestern margin of the Bering Sea, consists of zones of complexly deformed accreted terranes. Progressing from the northwestern Bering Sea inland are the Olyutorskiy, Ukelayat, and Koryak superterranes, which were accreted to the Okhotsk–Chukotsk volcanic–plutonic belt (OChVB) during the Campanian–Maastrichtian (Koryak) to Middle Eocene (Olyutorskiy), respectively. To constrain the accretion paleolatitude of the Koryak superterrane, we paleomagnetically sampled a sedimentary series on the Mametchinskiy Peninsula. At the Mametchinskiy Peninsula, in the northeastern Penzhinskaya Guba (61.45° N, 163.75° E), a gently deformed, well-bedded section of fine-grained Lower to lower Upper Cretaceous turbidites, the Mametchinskaya and Tylakrylskaya Formations are exposed. These strata, which represent the lower part of the sedimentary cover of the terranes in this region and the forearc of OChVB, were sampled at 39 sites (three to seven samples per site). Within the Ainyn terrane, more than 1000 m of section of Cenomanian–Turonian age was sampled at a basal locality (sample groups I and II, sites 1–18, 19–29) and at an upper locality of Valanginian–Barremian age (sample group III, sites 30–39) along the western shore of the Peninsula. Thermal demagnetization and principal component analysis of the demagnetization data show lower-temperature (A) and higher-temperature (B) magnetic components. Although group III samples did not display a coherent A component, the A component of group I and II samples was observed as a single-polarity lower-unblocking temperature component generally removed by 100–400 °C. This component failed the fold test at the 95% confidence level. With respect to direction, the A component is similar to both the present-day field and axial–geocentric dipole directions expected at this site. The B component was observed during thermal demagnetization steps up to 580 °C and was always of downward-directed inclination. Coherence of bedding corrections within each section do not allow statistically meaningful fold tests within groups I, II or III. Assuming the B component represents a Cretaceous magnetization, two overall models are proposed. In the first model (preferred), with the highest clustering of directions (k-value=36.7, N (sites)=36), indicates significant poleward motion of the Ainyn terrane (observed paleolatitude λ_M1=61.0±6.5°; expected North America plate reference site paleolatitude λ_E=74.0±3.5°). In the second model, no significant poleward displacement is implied (λ_M2=72.0±9.6).  相似文献   

Sources of granitoids in the Tuva-Mongolian microcontinent and surrounding structures: Evidence from Pb, Nd, and O isotopic systematics     

G. V. Ovchinnikova  D. P. Krylov  I. K. Kozakov  V. P. Kovach  N. A. Sergeeva 《Petrology》2009,17(6):570-578

Newly obtained data on Pb isotopic ratios in feldspars from Early Proterozoic granitoids of the Sangilen block of the Tuva-Mongolian microcontinent and Caledonian structures surrounding it, considered together with earlier data on the O and Nd isotopic systems, indicate that ancient (approximately 2 Ga) crustal material mixed in the sources of granites of the Tuva-Mongolian microcontinent with younger juvenile material. Positive ɛ_Nd values of granitoids from the Bashkimugor and Chgargalant massifs are accounted for by processes of crustal contamination during the interaction of the melt with crustal material. Similar Nd isotopic characteristics of granitoids in the Khoromnug pluton were caused by the melting of the Late Riphean crust. In granitoids of the massifs in the Kaakhem and Eastern Tannuola zones of the surrounding Caledonian structures, the involvement of juvenile material from oceanic crust increases away from the Sangilen block. Granites in the junction zone between the Tuva-Mongolian microcontinent and surrounding structures display evidence of the presence (up to 10–20%) of an ancient crustal component, and the melting history of granitoids in the Eastern Tannuola zone is dominated by an Early Paleozoic juvenile component in combination with material similar to the Vendian ophiolites of the Agardag-Erzin zone. An increase in the δ¹⁸O value, the ²⁰⁶Pb/²⁰⁴Pb ratio, and the T_Nd(DM) values within a single complex (from older to younger granitoid phases) is explained by the systematic involvement of crustal material in the melting processes.  相似文献   

Discovery of an optical flare from GRB 060926 by the MASTER robotic telescope: Possible formation of a marginally rotating black hole     

V. M. Lipunov  V. G. Kornilov  E. S. Gorbovskoy  A. V. Krylov  N. V. Tyurina  D. A. Kuvshinov  A. A. Belinski  P. A. Gritsyk  A. V. Sankovich  V. V. Vladimirov 《Astronomy Letters》2008,34(3):145-151

The MASTER robotic telescope has obtained the first optical images of GRB 060926. We have discovered an optical flare from GRB 060926, a recurrent brightening that closely follows its behavior in the X-ray range. We have determined the spectral slope for GRB 060926 from the X-ray to optical range in the first minutes. Based on the spinar model, we show that the parameters of the optical and X-ray flares suggest that the gamma-ray burst resulted from the core collapse of a 7M _⊙ star with an initial effective Kerr parameter of 7.6 and an initial magnetic-to-gravitational energy ratio of 10^?4.  相似文献   

High resolution method of direct measurement of the magnetic field lines'' eigen frequencies     

L.N. Baransky  J.E. Borovkov  M.B. Gokhberg  S.M. Krylov  V.A. Troitskaya 《Planetary and Space Science》1985,33(12):1369-1374

The simultaneous observations of Pc4 geomagnetic pulsations at the two temporary stations, located along the geomagnetic meridian 50 km to the North and South from the observatory Borok (L = 2.8), have been used for the investigation of amplitude gradients of both H- and D-components of these pulsations. It has been discovered that the direction of a meridional component of the gradient H (grad_MH) depends on the frequency ƒ of a spectral component of pulsations. The grad_MD is directed more or less permanently northward independently from the frequency ƒ These results are the consequence of a local amplification of geomagnetic pulsations due to Alfvén waves resonance along the magnetic field lines. It has been demonstrated that the frequencies ƒ_R for which the northward direction of grad_MH is replaced by the southward one (with increasing ƒ) can be interpreted as the eigen frequencies of the field line which intersects the meridian in the middle between two temporary stations, i.e. in Borok.

The possible applications of a gradient method of measurement of the magnetic field lines' eigen frequencies are discussed.  相似文献   

Causes of variations of Nd-O isotope ratios of granitoids in the Tuva-Mongolia microcontinent and its early Caledonian framing     

D. P. Krylov  I. K. Kozakov  V. A. Glebovitsky  A. M. Fedoseenko 《Doklady Earth Sciences》2006,409(5):762-764

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Anomalous 18O/16O ratios in the corundum-bearing rocks of Khitostrov, northern Karelia     

D. P. Krylov 《Doklady Earth Sciences》2008,419(2):453-456

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Modeling radionuclide migration in complex nonuniform water bodies using the POMRad model system     

A. L. Krylov  A. V. Nosov  V. P. Kiselev 《Russian Meteorology and Hydrology》2014,39(1):29-37

The POMRad system of computer models is developed using the Princeton Ocean Model (POM) program code. The system enables modeling the radionuclide migration in large nonuniform water bodies (seas, bays, large rivers, and lakes) taking account of the migration of radioactive substances in the water mass-bottom system associated with the migration of radionuclides sorbed on suspended sediments and in solutes. In order to take account of radionucide transport with sediments the POM program code is supplemented with the models describing transport, settling, and resuspension of suspended sediments. The verification was carried out through comparing analytical solutions of simplified problems concerning the content of radionuclides in water, and modeling results. A potential of the POMRad application is demonstrated by an example of simulating the radioactivity transport in marine environment in the case of hypothetical accidents in the Saida and Kola bays.  相似文献   

Hindcasting of Radioactive Contamination of the Kiev Reservoir Using Models of Various Detalisation     

Krylov  A. L.  Nosov  A. V.  Aron  D. V.  Merkushov  V. P. 《Russian Meteorology and Hydrology》2020,45(1):45-53

Russian Meteorology and Hydrology - Data of 137Cs measurements in the Kiev Reservoir after the Chernobyl accident were used for comparison of simulation results of two multi-chamber models of...  相似文献