Overview of Studies and the Modern Knowledge of Tonsteins (on the Occasion of the 150th Anniversary since the Beginning of Their Investigation)     

P. P. Timofeev  L. A. Admakin 《Lithology and Mineral Resources》2002,37(3):228-238

This work reviews the history of tonstein investigation and development of relevant lithogenetic ideas. Actual problems of further studies are formulated.  相似文献   

Hot Subdwarfs in Precataclysmic Binaries     

Vladislav Pustynski  Izold Pustylnik 《Astrophysics and Space Science》2006,304(1-4):267-270

We present a brief review of the recent results in modeling physical processes in strongly irradiated atmospheres of unevolved companions in precataclysmic binary systems (PCB) and their light curves. Constraints on physical parameters of the hot sdws primaries, thermal instability in upper irradiated atmosphere, monochromatic albedos, the deficit of the total emergent flux compared to the incoming flux from hot sdw primary are briefly discussed.  相似文献   

Thermal behavior of ferric selenite hydrates (Fe₂(SeO₃)₃·3H₂O,Fe₂(SeO₃)₃·5H₂O) and the water content in the natural ferric selenite mandarinoite     

Astrid Holzheid  Marina V. Charykova  Vladimir G. Krivovichev  Brendan Ledwig  Elena L. Fokina  Ksenia L. Poroshina  Natalia V. Platonova  Vladislav V. Gurzhiy 《Chemie der Erde / Geochemistry》2018,78(2):228-240

Any progress in our understanding of low-temperature mineral assemblages and of quantitative physico-chemical modeling of stability conditions of mineral phases, especially those containing toxic elements like selenium, strongly depends on the knowledge of structural and thermodynamic properties of coexisting mineral phases. Interrelation of crystal chemistry/structure and thermodynamic properties of selenium-containing minerals is not systematically studied so far and thus any essential generalization might be difficult, inaccurate or even impossible and erroneous. Disagreement even exists regarding the crystal chemistry of some natural and synthetic selenium-containing phases. Hence, a systematic study was performed by synthesizing ferric selenite hydrates and subsequent thermal analysis to examine the thermal stability of synthetic analogues of the natural hydrous ferric selenite mandarinoite and its dehydration and dissociation to unravel controversial issues regarding the crystal chemistry. Dehydration of synthesized analogues of mandarinoite starts at 56–87?°C and ends at 226–237?°C. The dehydration happens in two stages and two possible schemes of dehydration exist: (a) mandarinoite loses three molecules of water in the first stage of the dehydration (up to 180?°C) and the remaining two molecules of water will be lost in the second stage (>180?°C) or (b) four molecules of water will be lost in the first stage up to 180?°C and the last molecule of water will be lost at a temperature above 180?°C. Based on XRD measurements and thermal analyses we were able to deduce Fe₂(SeO₃)₃·(6-x)H₂O (x?=?0.0–1.0) as formula of the hydrous ferric selenite mandarinoite. The total amount of water apparently affects the crystallinity, and possibly the stability of crystals: the less the x value, the higher crystallinity could be expected.  相似文献   

Gradient-based Pareto optimal history matching for noisy data of multiple types     

Oleg Volkov  Vladislav Bukshtynov  Louis J. Durlofsky  Khalid Aziz 《Computational Geosciences》2018,22(6):1465-1485

The advantages of the simultaneous integration of production and time-lapse seismic data for history matching have been demonstrated in a number of previous studies. Production data provide accurate observations at particular spatial locations (wells), while seismic data enable global, though filtered/noisy, estimates of state variables. In this work, we present an efficient computational tool for bi-objective history matching, in which data misfits for both production and seismic measurements are minimized using an adjoint-gradient approach. This enables us to obtain a set of Pareto optimal solutions defining the optimal trade-off between production and seismic data misfits (which are, to some extent, conflicting). The impact of noise structure and noise level on Pareto optimal solutions is investigated in detail. We discuss the existence of the “best” trade-off solution, or least-conflicting posterior model, which corresponds to the history-matched model that is expected to provide the least-conflicting forecast of future reservoir performance. The overall framework is successfully applied in 2D and 3D compositional simulation problems to provide a single least-conflicting posterior model and, for the 2D case, multiple samples from the posterior distribution using the randomized maximum likelihood method.  相似文献   

A New Method for Low‐Temperature Decomposition of Chromites and Dichromium Trioxide using Bromic Acid Evaluated by Chromium Isotope Measurements     

Vladislav Chrastný  Jan Rohovec  Eva Čadková  Jan Pašava  Juraj Farkaš  Martin Novák 《Geostandards and Geoanalytical Research》2014,38(1):103-110

In recent years, routine application of the stable isotope determination of chromium (Cr) in environmental and health protection research has led to the search for simpler chromite decomposition techniques. As the range of Cr isotope abundance ratios in nature is very narrow, conventional chromite decomposition techniques are no longer suitable, due to the relatively high risk of contamination during laboratory procedures. We have developed a protocol for the decomposition of chromites based on oxidation by bromic acid at room temperature. The procedure takes 15 d and requires two doses of bromic acid during the reaction period (day 1 and 8), due to the limited stability of the reagent. Chromium extracted by alkaline oxidative fusion and by bromic acid decomposition yielded statistically indistinguishable δ⁵³Cr values, measured by multi‐collector inductively coupled plasma‐mass spectrometry following addition of a ⁵⁰Cr‐⁵⁴Cr double‐spike.  相似文献   

Kuranakh complex diabases in the western part of the Aldan-Stanovoi Shield: Age and tectonic setting     

N. V. Popov  A. B. Kotov  E. B. Salnikova  A. A. Postnikov  V. F. Timofeev  V. I. Berezkin  A. M. Larin  A. M. Fedoseenko  S. Z. Yakovleva 《Doklady Earth Sciences》2012,442(1):45-48

The age of Kuranakh Complex diabases in the western part of the Aldan-Stanovoi Shield determined by the zircon U-Pb method is virtually identical to that of basic rocks in the Chinei stratified pluton and granites in the Kodar Complex. Thus, it is possible to suggest that they form a unified bimodal magmatic association and belong to the South Siberian postcollision magmatic belt, which extends along the southwestern framing of the Siberian Craton for more than 2500 km from the Yenisei mountain range to the Aldan-Stanovoi Shield. The occurrence of the diabase dike swarms in magmatic associations of this belt testifies to formation under lithospheric extension conditions.  相似文献   

Strain and displacement rates during a large earthquake in the South Baikal region     

V.Yu. Timofeev  D.G. Ardyukov  E.V. Boyko  E.I. Gribanova  V.M. Semibalamut  A.V. Timofeev  A.V. Yaroshevich 《Russian Geology and Geophysics》2012,53(8):798-816

  相似文献   

Boundaries of mantle–lithosphere domains in the Bohemian Massif as extinct exhumation channels for high-pressure rocks     

Vladislav Babuška  Jaroslava Plomerová 《Gondwana Research》2013,23(3):973-987

Five domains (microplates) have been recognized by seismic anisotropy in the mantle lithosphere of the Bohemian Massif. The mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their Variscan assembly. The present-day mantle fabric indicates that this process consisted of at least three oceanic subductions, each followed by an underthrusting of the continental lithosphere. The seismic anisotropy does not detect remnants of the oceanic subductions, but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions. The most robust continent–continent collision was followed by westward underthrusting of the Brunovistulian mantle lithosphere, still detectable by seismic anisotropy more than 100 km beneath the Moldanubian mantle lithosphere. Major occurrences of the high-pressure/ultra high-pressure (HP–UHP) rocks follow the ENE and NNE oriented sutures and boundaries of the mantle–lithosphere domains mapped from three-dimensional modeling of body-wave anisotropy. The HP–UHP rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries. The close relation of the mantle sutures and occurrences of the HP–UHP rocks near the paleosubductions testifies for models interpreting the granulite–garnet peridotite association by oceanic/continental subduction/underthrusting followed by the exhumation of deep-seated rocks. Our findings support the bivergent subduction model of tectonic development of the central part of the Bohemian Massif. The inferences from seismic anisotropy image the Bohemian Massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric. The collisional mantle boundaries, blurred by tectonometamorphic processes in easily deformed overlying crust, served as major exhumation channels of the HP–UHP rocks.  相似文献   

Determining the accuracy of estimation of the two-dimensional stratospheric temperature field based on satellite measurements of limb radiation in the CO2 15-μm absorption band with high spectral resolution     

A. V. Rakitin  V. S. Kostsov  Yu. M. Timofeev 《Izvestiya Atmospheric and Oceanic Physics》2012,48(9):909-917

The problem of reconstructing the temperature distribution along optical paths from satellite measurements of the Earth’s limb radiation in the CO₂ 15-μm absorption band with a high spectral resolution is formulated and analyzed on the basis of numerical experiments performed in accordance with the MIPAS experiment. It is shown that the two-dimensional temperature field can be obtained through the processing of radiation measurements on paths with different target heights provided that spectral channels with essentially different optical thicknesses are used. The error in the stratospheric temperature determination varies from 1.8 to 5.6 K and depends on the target height of the optical path and the distance from the target point. The best horizontal resolution is 73–100 km, and it is achieved for optical paths with a target height of about 18–20 km.  相似文献   

Ground-based spectroscopic measurements of the total nitric acid content in the atmosphere     

S. G. Semakin  A. V. Poberovskii  Yu. M. Timofeev 《Izvestiya Atmospheric and Oceanic Physics》2013,49(3):294-297

The results of the first ground-based spectroscopic measurements in Russia of the total content (TC) of nitric acid in the atmosphere near St. Petersburg over the period April 2009–October 2011 are presented. These measurements show a substantial seasonal trend of the HNO₃ TC with maximal values in the winter period and early in the spring and minimal values in the summer time. The seasonal trends and variations in the daily mean values of HNO₃ TC near St. Petersburg in the winter and spring periods agree well with observations at the Kiruna station of the international NDACC network.  相似文献