The Kaidun meteorite: Clasts of alkaline‐rich fractionated materials     

Andrei V. Ivanov  Nataliya N. Kononkova  S. Vincent Yang  Michael E. Zolensky 《Meteoritics & planetary science》2003,38(5):725-737

Abstract— Clasts of alkaline (the second find in meteorites) and subalkaline rocks were found in the Kaidun meteorite. One of them (#d4A) is a large crystal of albite with inclusions of fluorapatite, arfvedsonite, aenigmatite, and wilkinsonite. The two latter minerals were previously unknown in meteorites. Another clast (#d[3–5]D) has a melt crystallization texture of mainly feldspar (oligoclase) composition and contains relict grains of both high‐Ca and low‐Ca pyroxene and fluorapatite. The mineralogical characteristics of these clasts suggest a genetic relationship and an origin from the same parent body. The textural and mineralogical characteristics of the clasts indicate origin by extensive igneous differentiation. Such processes most likely took place in a rather large differentiated body. The material of clast #d(3–5)D is similar in some mineralogical respects to basaltic shergottites.  相似文献   

Spectroscopic Redshift Determination for a Sample of Distant Quasars Detected by the SRG Observatory Based on RTT-150 Observations. II     

Bikmaev  I. F.  Irtuganov  E. N.  Nikolaeva  E. A.  Sakhibullin  N. A.  Gumerov  R. I.  Sklyanov  A. S.  Glushkov  M. V.  Khamitov  I. M.  Borisov  V. D.  Burenin  R. A.  Zaznobin  I. A.  Krivonos  R. A.  Lyapin  A. R.  Medvedev  P. S.  Meshcheryakov  A. V.  Sazonov  S. Yu.  Sunyaev  R. A.  Khorunzhev  G. A.  Gilfanov  M. R. 《Astronomy Letters》2021,47(5):277-290

Astronomy Letters - Results of the spectroscopic observations at the 1.5-m Russian–Turkish telescope for another group of 12 X-ray sources discovered by the eROSITA telescope onboard the SRG...  相似文献   

Numerical modelling of stratified tidal flow over a fjord sill     

Nataliya Stashchuk  Vasiliy Vlasenko 《Ocean Dynamics》2007,57(4-5):325-338

Field observations of tidally driven stratified flow in the sill area of Knight Inlet (British Columbia) revealed a very complicated structure, which includes solitary waves, upstream bifurcation, hydraulic jump and mixing processes. Recent observations suggest that the flow instabilities on the plunging pycnocline at the lee side of the sill may contribute to solitary wave generation through a subharmonic interaction. The present study reports on a series of numerical experiments of stratified tidal flow in Knight Inlet performed with the help of a fine resolution fully non-linear non-hydrostatic numerical model. The model reproduces all important stages of the baroclinic tidal dynamics observed in Knight Inlet. Results demonstrate that solitary waves are generated apart from the area of hydrodynamic instability. Accelerating tidal flux forms a baroclinic hydraulic jump just above the top of the sill, whereas the bifurcations and zones of shear instabilities are formed downstream of the sill. The first baroclinic mode having the largest velocity escapes from the generation area and propagates upstream, disintegrating further into a packet of solitary waves reviling the classical “non-subharmonic” mechanism of generation. The remaining part of the disturbance (slow baroclinic modes) is arrested by tidal flow and carried away to the lee side of the obstacle, where shear instability, billows and mixing processes are developed. Some sensitivity runs were performed for different value of tidal velocity.  相似文献   

Experimental studies of Ta2O5 and columbite–tantalite solubility in fluoride solutions from 300 to 550°C and 50 to 100 MPa     

George Pavlovich Zaraisky  Valentina Korzhinskaya  Nataliya Kotova 《Mineralogy and Petrology》2010,99(3-4):287-300

It is well established that the fractionation of Li–F granitic magmas at depth leads to the accumulation of flux elements such as F and Li, and metal cations such as Ta and Nb in residual melts. However, it remains to be determined whether magmatic fractionation is sufficient to concentrate Nb and Ta into economically significant quantities, and what role hydrothermal–metasomatic processes play in the formation of such ore deposits. In the literature, reliable data about the solubility of Ta and Nb in hydrothermal solutions is missing or incomplete. This study provides a quantitative experimental estimation of the possible contribution from hydrothermal processes in Ta enrichment in cupolas of albitized and greisenized Li–F granite. Experimental studies of Ta₂O₅ and columbite–tantalite (Mn,Fe)(Nb,Ta)₂O₆ solubility were carried out in fluoride solutions consisting of HF, NaF, KF, and LiF. At low fluoride concentrations (0.01 and 0.1 m), Ta₂O₅ solubility at 550°C and 100 MPa under Co–CoO oxidizing conditions is low (near 10^?5–10^?4 m) in all fluoride solutions (HF, NaF, KF, LiF). At high fluoride concentrations (1 and 2 m) the highest Ta₂O₅ concentrations (10^?1 m) were detected in HF solutions. In KF, NaF, and LiF solutions, the Ta₂O₅ solubility is also high (10^?3–10^?2 m). The dependence of columbite–tantalite (Nb₂O₅-59 wt. %, Ta₂O₅-18 wt. %) solubility as a function of solution composition, T, and P has also been investigated. Tantalum and Nb concentrations have the highest values in HF solutions at reduced conditions (up to 10^?3 to 10^?2 m Ta in 1 m HF). In 1 m NaF solutions, the concentrations of Nb and Ta are, respectively, 2.5 and 3 orders of magnitude less than those in the 1 m HF solutions. Solubility of Ta and Nb in KF solutions has intermediate values. It is established that in NaF and KF solutions the dependence of solubility on pressure is distinctly negative. The Nb and Ta contents increase with increasing concentrations of HF and KF in solution, however, they do not change with increasing NaF concentration. In NaHCO₃, Na₂CO₃, and HCl solutions columbite–tantalite solubility is low. Even in 1 m chloride solutions the content is within the limits of 10^?5 m for Nb and 10^?6 to 10^?8 m for Ta. We conclude that hydrothermal transport of Ta and Nb is possible only in concentrated fluoride solutions.  相似文献   

The NLTE Formation of Iron Lines Used in Solar Polarimetry     

Shchukina  Nataliya G.  Bueno  Javier Trujillo  Kostik  Roman I. 《Solar physics》1997,172(1-2):117-124

We study in some detail one-dimensional NLTE effects in solar Fei lines. The lines selected are frequently used in solar polarimetry, and also in studies of line asymmetries and for abundance determinations. Our model atom for Fei–Feii–Feiii is realistic: it takes account of multiplet structure and it includes over 200 bound–bound and bound–free transitions in detail. We use very efficient iterative methods for the self-consistent solution of the kinetic and radiative transfer equations (Auer, Fabiani Bendicho, and Trujillo Bueno, 1994). We have applied these fast methods of solution because they are suitable for the investigation of 2D and 3D NLTE transfer effects with multilevel atoms, which constitutes the next step of our ongoing research project on the iron line formation problem.  相似文献   

Detailed mineralogical-geochemical study of a large spinel Lherzolite xenolith in alkali basalt of Shavaryn Tsaram paleovolcano,Mongolia     

F. P. Lesnov  S. V. Palesskii  I. V. Nikolaeva  O. A. Koz’menko  A. M. Kuchkin  V. N. Korolyuk 《Geochemistry International》2009,47(1):18-40

Mineralogical-geochemical data obtained on a large xenolith of spinel lherzolite from basanites of Shavaryn Tsaram volcano (Middle Pleistocene) provide evidence that the xenolith was affected by heat and fluid that came from the basalt melt and induced geochemical heterogeneity of the xenolith. Olivine crystals from the central portion of the xenolith contain much more CaO than this mineral from the peripheral zones of the xenolith as well as in xenocrystals of the host basalts. The large xenolith was unevenly annealed by the host basalt melt, and this predetermined the heterogeneous diffusion-controlled “purification” of olivine crystals from their CaO admixture. The xenolith is heterogeneously enriched in LREE and some trace elements (Zr, Hf, Nb, Th, and U), and their distribution demonstrates unclearly pronounced concentric zoning: these elements enriched the outer portions of the xenolith. The enrichment of the xenolith in LREE and other mobile trace elements is explained by their occurrence not only as structurally bound (isomorphic) components in minerals but also in the form of nonstructural admixtures (contaminant), as minute grains of compounds hosted in the interstitial space and tiny cracks cutting mineral grains. The enrichment of the xenolith in these admixtures proceeded via their infiltration-controlled introduction with fluid from the basalt along minute cracks.  相似文献   

Dependence of energy consumption on air temperature in Moscow     

M. A. Lokoshchenko  N. A. Nikolaeva 《Russian Meteorology and Hydrology》2017,42(12):783-791

The dependence of energy consumption on air temperature for every day of the period from 1990 to 2015 is for the first time studied for mid-latitudes using the long-term observational data of the Moscow State University Meteorological Observatory. It is demonstrated that this dependence is generally descending in the Moscow region: energy consumption decreases as air temperature rises. At the same time, the energy consumption increase slows down due to energy saving in case of severe frosts, whereas the opposite trend is manifested in case of abnormally hot weather, that is, the energy consumption increase along with the air temperature rise due to additional consumption for air conditioning. The optimum temperature for energy saving is 18°C. The relationship between energy consumption and air humidity characteristics is analyzed. There is almost no link with relative humidity, while in the link with the partial pressure of water vapor, the dependence of the latter on air temperature is reflected indirectly.  相似文献   

Hydrocarbon generation in the interiors of Kamchatka and its relationship to volcanism and hydrothermal activity     

A. I. Pozdeev  A. G. Nikolaeva 《Journal of Volcanology and Seismology》2012,6(1):31-48

This paper considers oil-and-gas provinces and the epochs of hydrocarbon generation in Kamchatka. We distinguish the following epochs of hydrocarbon generation: the Early Mesozoic, the Early Cretaceous, the Late Cretaceous, the Early Paleogene, the Late Paleogene, the Miocene, and the Pliocene-Quaternary. We emphasize the fact that all gas generation epochs were related to deep processes, including volcanism and hydrothermal activity.  相似文献   

How Bayesian data assimilation can be used to estimate the mathematical structure of a model   总被引：1，自引：1，他引：0  

Nataliya Bulygina  Hoshin Gupta 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(6):925-937

In previous work, we presented a method for estimation and correction of non-linear mathematical model structures, within a Bayesian framework, by merging uncertain knowledge about process physics with uncertain and incomplete observations of dynamical input-state-output behavior. The resulting uncertainty in the model input-state-output mapping is expressed as a weighted combination of an uncertain conceptual model prior and a data-derived probability density function, with weights depending on the conditional data density. Our algorithm is based on the use of iterative data assimilation to update a conceptual model prior using observed system data, and thereby construct a posterior estimate of the model structure (the mathematical form of the equation itself, not just its parameters) that is consistent with both physically based prior knowledge and with the information in the data. An important aspect of the approach is that it facilitates a clear differentiation between the influences of different types of uncertainties (initial condition, input, and mapping structure) on the model prediction. Further, if some prior assumptions regarding the structural (mathematical) forms of the model equations exist, the procedure can help reveal errors in those forms and how they should be corrected. This paper examines the properties of the approach by investigating two case studies in considerable detail. The results show how, and to what degree, the structure of a dynamical hydrological model can be estimated without little or no prior knowledge (or under conditions of incorrect prior information) regarding the functional forms of the storage–streamflow and storage–evapotranspiration relationships. The importance and implications of careful specification of the model prior are illustrated and discussed.  相似文献   

Characteristic features of the occurrence of gas-fluid emanations on the northeastern slope of Sakhalin Island, Sea of Okhotsk     

N. A. Nikolaeva  A. N. Derkachev  A. I. Obzhirov 《Russian Journal of Pacific Geology》2009,3(3):234-248

This paper summarizes the results of combined studies in the areas of the occurrence of gas-fluid emanations in the water column, on the seafloor, and in the upper part of the sedimentary section on the northeastern slope of Sakhalin Island (Sea of Okhotsk). The phenomena typical of methane seeps were characterized in detail: the presence of acoustic anomalies, high concentrations of methane in the water and sediments, and the specific features of the sedimentary section (the textural and structural features, the character of the mineral inclusions and gas hydrates, and the chemical composition). The component composition of the gases (including the accompanying gas hydrates), which is almost free of heavy hydrocarbon homologues of methane; the light carbon isotopic compositions of the methane and carbonate concretions; and the low temperatures of the near-bottom water and sediments suggest that the occurrence of numerous methane emanations is related to gas generation in the upper part of the sedimentary sequence. No evidence was found for the existence of a deep center of gas formation within the seafloor area considered. Typical submarine mud volcanic edifices were also not found.  相似文献