Thermoelastic properties of chromium oxide Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> (eskolaite) at high pressures and temperatures     

Anna M. Dymshits  Peter I. Dorogokupets  Igor S. Sharygin  Konstantin D. Litasov  Anton Shatskiy  Sergey V. Rashchenko  Eiji Ohtani  Akio Suzuki  Yuji Higo 《Physics and Chemistry of Minerals》2016,43(6):447-458

A new synchrotron X-ray diffraction study of chromium oxide Cr₂O₃ (eskolaite) with the corundum-type structure has been carried out in a Kawai-type multi-anvil apparatus to pressure of 15 GPa and temperatures of 1873 K. Fitting the Birch–Murnaghan equation of state (EoS) with the present data up to 15 GPa yielded: bulk modulus (K _0,T0), 206 ± 4 GPa; its pressure derivative K′_0,T , 4.4 ± 0.8; (?K _0,T /?T) = ?0.037 ± 0.006 GPa K^?1; a = 2.98 ± 0.14 × 10^?5 K^?1 and b = 0.47 ± 0.28 × 10^?8 K^?2, where α _0,T  = a + bT is the volumetric thermal expansion coefficient. The thermal expansion of Cr₂O₃ was additionally measured at the high-temperature powder diffraction experiment at ambient pressure and α _0,T0 was determined to be 2.95 × 10^?5 K^?1. The results indicate that coefficient of the thermal expansion calculated from the EoS appeared to be high-precision because it is consistent with the data obtained at 1 atm. However, our results contradict α ₀ value suggested by Rigby et al. (Brit Ceram Trans J 45:137–148, 1946) widely used in many physical and geological databases. Fitting the Mie–Grüneisen–Debye EoS with the present ambient and high-pressure data yielded the following parameters: K _0,T0 = 205 ± 3 GPa, K′_0,T  = 4.0, Grüneisen parameter (γ ₀) = 1.42 ± 0.80, q = 1.82 ± 0.56. The thermoelastic parameters indicate that Cr₂O₃ undergoes near isotropic compression at room and high temperatures up to 15 GPa. Cr₂O₃ is shown to be stable in this pressure range and adopts the corundum-type structure. Using obtained thermoelastic parameters, we calculated the reaction boundary of knorringite formation from enstatite and eskolaite. The Clapeyron slope (with \({\text{d}}P/{\text{d}}T = - 0.014\) GPa/K) was found to be consistent with experimental data.  相似文献   

Hydrogen bonding system in euchroite,Cu2(AsO4)(OH)(H2O)3: low-temperature crystal-structure refinement and solid-state density functional theory modeling     

Sergey V. Krivovichev  Andrey A. Zolotarev  Igor V. Pekov 《Mineralogy and Petrology》2016,110(6):877-883

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Jusa and Barsuchi Log Volcanogenic Massive Sulfide Deposits from the Southern Urals of Russia: Devonian Analogs of the Kuroko Deposits of NE Honshu, Japan     

Geoffrey P. Glasby    Valery V. Maslennikov    Irina A. Prozherova  Sergey I. Petukhov 《Resource Geology》2008,58(3):313-324

Chemical analysis of 60 samples from the Jusa and Barsuchi Log volcanogenic massive sulfide (VMS) deposits by inductively coupled plasma–mass spectrometry shows that, on average, the Jusa deposit is more enriched in the chalcophilic elements than the Barsuchi Log deposit, whereas the Barsuchi Log deposit is more enriched in the lithogenous elements and Te. In addition, the yellow ores in these deposits are more enriched on average in Cu, As and Mo and the black ores more enriched in Zn, Ga, Cd, Sb, Ba , Hg and Pb relative to each other. Both these deposits are similar in composition to the Kuroko deposits of NE Honshu and may be considered to be analogs of these deposits. The Kuroko deposits, however, contain much higher concentrations of As, Ag, Sb, Ba, Hg and lower contents of Te on average than the Jusa and Barsuchi Log deposits. Based on the higher contents of Te in the Barsuchi Log deposit compared to the Jusa deposit, as well as on textural considerations, it is concluded that the Barsuchi Log deposit is intermediate between the Urals- and Kuroko-type deposits, whereas the Jusa deposit is more analogous to the Kuroko-type deposits. Based on the compositional data presented here, the Jusa and Barsuchi Log deposits may be described as Zn-Pb-Cu-Ba deposits rather than as Zn-Cu-Ba deposits, as the Baimak-type deposits of the west Magnitogrosk zone have previously been described.  相似文献   

Quantifying and Modelling the Effect of Cloud Shadows on the Surface Irradiance at Tropical and Midlatitude Forests     

Sergey N. Kivalov  David R. Fitzjarrald 《Boundary-Layer Meteorology》2018,166(2):165-198

Cloud shadows lead to alternating light and dark periods at the surface, with the most abrupt changes occurring in the presence of low-level forced cumulus clouds. We examine multiyear irradiance time series observed at a research tower in a midlatitude mixed deciduous forest (Harvard Forest, Massachusetts, USA: \(42.53{^{\circ }}\hbox {N}\), \(72.17{^{\circ }}\hbox {W}\)) and one made at a similar tower in a tropical rain forest (Tapajós National Forest, Pará, Brazil: \(2.86{^{\circ }}\hbox {S}\), \(54.96{^{\circ }}\hbox {W}\)). We link the durations of these periods statistically to conventional meteorological reports of sky type and cloud height at the two forests and present a method to synthesize the surface irradiance time series from sky-type information. Four classes of events describing distinct sequential irradiance changes at the transition from cloud shadow and direct sunlight are identified: sharp-to-sharp, slow-to-slow, sharp-to-slow, and slow-to-sharp. Lognormal and the Weibull statistical distributions distinguish among cloudy-sky types. Observers’ qualitative reports of ‘scattered’ and ‘broken’ clouds are quantitatively distinguished by a threshold value of the ratio of mean clear to cloudy period durations. Generated synthetic time series based on these statistics adequately simulate the temporal “radiative forcing” linked to sky type. Our results offer a quantitative way to connect the conventional meteorological sky type to the time series of irradiance experienced at the surface.  相似文献   

A GIS-based modeling of snow accumulation and melt processes in the Votkinsk reservoir basin     

Sergey V. Pyankov  Andrey N. Shikhov  Nikolay A. Kalinin  Eugene M. Sviyazov 《地理学报(英文版)》2018,28(2):221-237

Coupled hydrological and atmospheric modeling is an efficient method for snowmelt runoff forecast in large basins. We use short-range precipitation forecasts of mesoscale atmospheric Weather Research and Forecasting (WRF) model combining them with ground-based and satellite observations for modeling snow accumulation and snowmelt processes in the Votkinsk reservoir basin (184,319 km²). The method is tested during three winter seasons (2012–2015). The MODIS-based vegetation map and leaf area index data are used to calculate the snowmelt intensity and snow evaporation in the studied basin. The GIS-based snow accumulation and snowmelt modeling provides a reliable and highly detailed spatial distribution for snow water equivalent (SWE) and snow-covered areas (SCA). The modelling results are validated by comparing actual and estimated SWE and SCA data. The actual SCA results are derived from MODIS satellite data. The algorithm for assessing the SCA by MODIS data (ATBD-MOD 10) has been adapted to a forest zone. In general, the proposed method provides satisfactory results for maximum SWE calculations. The calculation accuracy is slightly degraded during snowmelt periods. The SCA data is simulated with a higher reliability than the SWE data. The differences between the simulated and actual SWE may be explained by the overestimation of the WRF-simulated total precipitation and the unrepresentativeness of the SWE measurements (snow survey).  相似文献   

Recent changes in the active layer thickness across the northern hemisphere   总被引：1，自引：0，他引：1  

Dongliang Luo  Qingbai Wu  Huijun Jin  Sergey S. Marchenko  Lanzhi Lü  Siru Gao 《Environmental Earth Sciences》2016,75(7):555

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Simulation of Hydraulic Heterogeneity and Upscaling Permeability and Dispersivity in Sandy-Clay Formations     

Veronika A. Bakshevskaia  Sergey P. Pozdniakov 《Mathematical Geosciences》2016,48(1):45-64

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Seasonal variability in Atlantic Water off Spitsbergen     

Vladimir V. Ivanov  Igor V. Polyakov  Igor A. Dmitrenko  Edmond Hansen  Irina A. Repina  Sergey A. Kirillov  Cecillie Mauritzen  Harper Simmons  Leonid A. Timokhov 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):1-14

A combination of 2-year-long mooring-based measurements and snapshot conductivity–temperature–depth (CTD) observations at the continental slope off Spitsbergen (81°30′N, 31°00′E) is used to demonstrate a significant hydrographic seasonal signal in Atlantic Water (AW) that propagates along the Eurasian continental slope in the Arctic Ocean. At the mooring position this seasonal signal dominates, contributing up to 50% of the total variance. Annual temperature maximum in the upper ocean (above 215 m) is reached in mid-November, when the ocean in the area is normally covered by ice. Distinct division into ‘summer’ (warmer and saltier) and ‘winter’ (colder and fresher) AW types is revealed there. Estimated temperature difference between the ‘summer’ and ‘winter’ waters is 1.2 °C, which implies that the range of seasonal heat content variations is of the same order of magnitude as the mean local AW heat content, suggesting an important role of seasonal changes in the intensity of the upward heat flux from AW. Although the current meter observations are only 1-year long, they hint at a persistent, highly barotropic current with little or no seasonal signal attached.  相似文献   

A new mineral species rossovskyite, (Fe3+,Ta)(Nb,Ti)O4: crystal chemistry and physical properties     

Sergey I. Konovalenko  Sergey A. Ananyev  Nikita V. Chukanov  Ramiza K. Rastsvetaeva  Sergey M. Aksenov  Anna A. Baeva  Ramil R. Gainov  Farit G. Vagizov  Oleg N. Lopatin  Tatiana S. Nebera 《Physics and Chemistry of Minerals》2015,42(10):825-833

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Inferring protoliths of high-grade metamorphic gneisses of the Erzgebirge using zirconology,geochemistry and comparison with lower-grade rocks from Lusatia (Saxothuringia,Germany)     

Marion Tichomirowa  Sergey Sergeev  Hans-Jürgen Berger  Dietmar Leonhardt 《Contributions to Mineralogy and Petrology》2012,164(3):375-396

Protoliths of highly metamorphosed gneisses from the Erzgebirge are deduced from the morphology, age and chemistry of zircons as well as from whole rock geochemistry and are compared with lower-grade rocks of Lusatia. Gneisses with similar structural appearance and/or geochemical pattern may have quite different protoliths. The oldest rocks in the Erzgebirge are paragneisses representing meta-greywackes and meta-conglomerates. The youngest group of zircon of meta-greywackes that did not undergo Pb loss represents the youngest igneous component for source rocks (about 575 Ma). Similar ages and zircon morphology reflect the subordinate formation of new zircon grains or only zircon rims in the augengneiss from Bärenstein and Wolkenstein, which probably represent metamorphic equivalents to Lower Cambrian two-mica granodiorites from Lusatia. Bulk rock chemistry, intense fracturing and high U and Th concentrations of zircons suggest deformation-induced and fluid-enhanced recrystallisation of zircon grains. Temperatures during tectonic overprinting—too low to reset zircon ages—indicate mid- or upper crustal levels for shearing recorded in these augengneisses. Lower Cambrian (~540 Ma) granodiorites are widespread in Lusatia but are exclusively represented by the Freiberg gneiss dome in the Eastern Erzgebirge. Ordovician protolith ages were recorded by zircons from the augengneisses of the Reitzenhain–Catherine dome and the Schwarzenberg dome (Western Erzgebirge) documenting significant regional differences between the eastern and the western Erzgebirge (~540 vs. ~490 Ma). In the Western Erzgebirge, most meta-volcanic rocks (muscovite gneisses) and meta-granites (mainly red augengneisses) yield Ordovician zircon ages, whereas in the Eastern part, similar rocks mainly recorded Lower Cambrian protolith ages. Zircon overprinting was highest within discrete tectonic zones where the combination of fluid infiltration and deformation induced variable degrees of recrystallisation and formation of a new augengneiss structure. Variable degrees of Pb loss caused age shifts that do not correspond to changes in zircon morphology but may be associated with U and Th enrichments. Major changes in bulk rock composition appear to be restricted to discrete zones and to (U)HP nappes, whereas gneisses with a MP–MT metamorphic overprint basically show no geochemical modifications.  相似文献