Paleomagnetism, microplates and Siberian plate consolidation     

A.N Khramov  E.L Gurevich  R.A Komissarova  E.P Osipova  S.A Pisarevsky  V.P Rodionov  I.P Slautsitais 《Journal of Geodynamics》1985,2(2-3)

Paleomagnetic research in the Siberian area provides new data to derive models of relative horizontal movements and the process of amalgamation or consolidation of the Siberian plate. Comparison of the Apparent Polar Wander (APW) curves for different regions of Siberia show that there were several stages of plate consolidation, the most important of which belonged to Baikalian time (c. 520–800 Ma). The consolidation was complicated by rifting processes. There were six megaterrains in pre-Vendian times, which underwent differential horizontal displacements. The joining of the Altai-Sayan fold area and the North-East microplates and fold belts to the Siberian plate, and the separation of the Taimyr peninsula, were the main post-Baikalian events. The most complete geologic sections were studied in conjunction with radiometric age dating and related to the geochronological Precambrian time scale of the USSR. This has led to the discovery of a stratigraphic polarity bias in the early Riphean-Vendian interval. There were five polarity stages in this interval 200–240 Ma each.  相似文献   

Geological structure, composition, and age of the Pyalochnoozero ultramafic-mafic massif, northeastern Baltic Shield     

V. K. Kuz&#;min  M. V. Naumov  N. G. Berezhnaya  N. V. Rodionov 《Doklady Earth Sciences》2007,413(2):173-177

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On the 90th anniversary of the birth of Igor Ippolitovich Bersenev     

A. I. Khanchuk  S. M. Rodionov  G. L. Kirillova 《Russian Journal of Pacific Geology》2007,1(2):200-201

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Zirconology of ultramafic rocks from the Vostochnotagilskii massif (Middle Urals)     

A. A. Krasnobaev  A. I. Rusin  S. V. Busharina  N. V. Rodionov 《Doklady Earth Sciences》2014,455(2):441-445

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Zircon trace element characteristics and ages in granulite xenoliths: a key to understanding the age and origin of the lower crust,Arkhangelsk kimberlite province,Russia     

M.?Yu.?KoreshkovaEmail author  H.?Downes  V.?A.?Glebovitsky  N.?V.?Rodionov  A.?V.?Antonov  S.?A.?Sergeev 《Contributions to Mineralogy and Petrology》2014,167(2):973

Garnet granulite and pyroxenite xenoliths from the Grib kimberlite pipe (Arkhangelsk, NW Russia) represent the lower crust beneath Russian platform in close vicinity to the cratonic region of the north-eastern Baltic (Fennoscandian) Shield. Many of the xenoliths have experienced strong interaction with the kimberlite host, but in others some primary granulite-facies minerals are preserved. Calculated bulk compositions for the granulites suggest that their protoliths were basic to intermediate igneous rocks; pyroxenites were ultrabasic to basic cumulates. A few samples are probably metasedimentary in origin. Zircons are abundant in the xenoliths; they exhibit complex zoning in cathodoluminescence with relic cores and various metamorphic rims. Cores include oscillatory zircon crystallized in magmatic protoliths, and metamorphic and magmatic sector-zoned zircons. Recrystallization of older zircons led to the formation of bright homogeneous rims. In some samples, homogeneous shells are surrounded by darker convoluted overgrowths that were formed by subsolidus growth when a change in mineral association occurred. The source of Zr was a phase consumed during a reaction, which produced garnet. Late-generation zircons in all xenoliths show concordant U–Pb ages of 1.81–1.84 Ga (1,826 ± 11 Ma), interpreted as the age of last granulite-facies metamorphism. This event completely resets most zircon cores. An earlier metamorphic event at 1.96–1.94 Ga is recorded by some rare cores, and a few magmatic oscillatory zircons have retained a Neoarchaean age of 2,719 ± 14 Ma. The assemblage of metaigneous and metasedimentary rocks was probably formed before the event at 1.96 Ga. Inherited magmatic zircons indicate the existence of continental crust by the time of intrusion of magmatic protoliths in the Late Archaean. The U–Pb zircon ages correspond to major events recorded in upper crustal rocks of the region: collisional metamorphism and magmatism 2.7 Ga ago and reworking of Archaean rocks at around 1.95–1.75 Ga. However, formation of the granulitic paragenesis in lower crustal rocks occurred significantly later than the last granulite-facies event seen in the upper crust and correlates instead with retrograde metamorphism and small-volume magmatism in the upper crust.  相似文献   

Estimating the dark halo mass from the relative thickness of stellar disks     

N. Ya. Sotnikova  S. A. Rodionov 《Astronomy Letters》2006,32(10):649-660

We analyze the relationship between the mass of a spherical component and the minimum possible thickness of stable stellar disks. This relationship for real galaxies allows the lower limit on the dark halo mass to be estimated (the thinner the stable stellar disk is, the more massive the dark halo must be). In our analysis, we use both theoretical relations and numerical N-body simulations of the dynamical evolution of thin disks in the presence of spherical components with different density profiles and different masses. We conclude that the theoretical relationship between the thickness of disk galaxies and the mass of their spherical components is a lower envelope for the model data points. We recommend using this theoretical relationship to estimate the lower limit for the dark halo mass in galaxies. The estimate obtained turns out to be weak. Even for the thinnest galaxies, the dark halo mass within four exponential disk scale lengths must be more than one stellar disk mass.  相似文献   

X-ray pre-ionization powered by accretion on the first black holes – II. Cosmological simulations and observational signatures     

Massimo Ricotti  Jeremiah P. Ostriker  Nickolay Y. Gnedin 《Monthly notices of the Royal Astronomical Society》2005,357(1):207-219

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Present situation and development of mathematical geology in Russia     

D. A. Rodionov 《Mathematical Geology》1995,27(6):807-810

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Fluctuations of hydrophysical fields induced by oceanic acoustic noises     

V. I. Babii  A. A. Rodionov 《Doklady Earth Sciences》2014,456(1):567-571

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The neural network approximation method for solving multidimensional nonlinear inverse problems of geophysics     

M. I. Shimelevich  E. A. Obornev  I. E. Obornev  E. A. Rodionov 《Izvestiya Physics of the Solid Earth》2017,53(4):588-597

The iterative approximation neural network method for solving conditionally well-posed nonlinear inverse problems of geophysics is presented. The method is based on the neural network approximation of the inverse operator. The inverse problem is solved in the class of grid (block) models of the medium on a regularized parameterization grid. The construction principle of this grid relies on using the calculated values of the continuity modulus of the inverse operator and its modifications determining the degree of ambiguity of the solutions. The method provides approximate solutions of inverse problems with the maximal degree of detail given the specified degree of ambiguity with the total number of the sought parameters ~n × 10³ of the medium. The a priori and a posteriori estimates of the degree of ambiguity of the approximated solutions are calculated. The work of the method is illustrated by the example of the three-dimensional (3D) inversion of the synthesized 2D areal geoelectrical (audio magnetotelluric sounding, AMTS) data corresponding to the schematic model of a kimberlite pipe.  相似文献