Erosion level of the epithermal Rogovik deposit estimated from geochemical data,northeast Russia     

R. G. Kravtsova  A. S. Makshakov 《Geology of Ore Deposits》2016,58(6):485-498

The geochemical zoning of the Rogovik epithermal deposit in northeast Russia has been established on the basis of endogenic anomalous geochemical fields (AGCF) of Au–Ag zones, their qualitative and quantitative compositions, and spatial distribution of chemical element indicators of Au–Ag mineralization. The obtained geochemical data (monoelemental AGCF, associations of elements, their composition, contrast, and correlation) allowed us to estimate the erosion level of Au–Ag ore zones. It has been shown that AGCF related to Au–Ag mineralization are distinguished by simple component composition (Au, Ag, Hg, Sb, As, Cu, Pb, Zn) and regular spatial distribution of the elements. It has been established that the least eroded central part of the object is characterized by widespread and the most contrasting Au, Ag, Hg, Sb, and As AGCF closely related to the ore-bearing units of the deposit. The contrast of these fields gradually decreases with depth. Low-contrast Cu, Pb, and Zn AGCF typical of the footwall depth intervals and flanks of Au–Ag zones intervals appear at depth. The northern part of the area is eroded to the deepest level. The contrast of Ag, Hg, Sb, and As geochemical fields abruptly decreases here, and Cu, Pb, and Zn AGCF become widespread with depth. The relatively contrasting fields of anomalous Au concentrations develop here extremely locally and near the surface. It has been concluded that the as yet poorly explored southern part of the Rogovik deposit most likely is promising for further geological exploration and the discovery of new mineralized areas.  相似文献   

Occurrence Forms of Carbon,Sulfur, and Noble Metals in Deposits of the Black-Shale Formation by the Example of the Degdekan Gold-Ore Deposit (Northeastern Russia)     

V. L. Tauson  R. G. Kravtsova  V. V. Akimov  S. V. Lipko  A. M. Spiridonov  A. E. Budyak  I. Yu. Voronova  O. Yu. Belozerova  K. Yu. Arsentev 《Doklady Earth Sciences》2018,478(1):92-99

Pyrite crystals and ore-bearing shales of the Degdekan deposit were studied by means of XPS, SEM–EDX, EPMA, and AAS. Five peaks of carbon organic forms were identified, conforming to polymer compounds containing either double bonds of carbon or alkyne groups and compounds containing C–OH and C=O bonds, as well as, probably, small amounts of S-containing compounds and those with functional groups of carboxylic acids. Sulfate prevails over sulfite in pyrites; among the surface sulfide forms, disulfide prevails over monosulfide; the presence of polysulfide is registered. The occurrence of various chemical forms of sulfur on the surface might provide for concentrating of microelements including the noble metals (NMs) in their surface-bound forms. The regular behavior of NMs (Au, Pt, Pd, and Ru) depending on the grain sizes (specific surfaces) of pyrite crystals along with the narrow range of the ratios of structural and surface components of the concentrations of different NMs points to NM coprecipitation with pyrite during the same productive stage. No capture of NM-containing carbonaceous phases took place, which should violate the regularity of Au distribution in pyrites of the Sukhoi Log deposit.  相似文献   

BEHAVIOUR OF NITRATE IN A HETEROGENEOUS FIELD SOIL: MEASUREMENTS AND MODELLING ON DIFFERENT SPATIAL SCALES     

JÜRG HOSANG 《水文研究》1996,10(9):1193-1208

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Peculiarities of the UV continuum energy distribution for T Tauri stars     

A. S. Kravtsova  S. A. Lamzin 《Astronomy Letters》2003,29(9):612-620

In the UV spectra of BP Tau, GW Ori, T Tau, and RY Tau obtained with the Hubble Space Telescope, we detected an inflection near 2000 Å in the F _λ ^c (λ) curve that describes the continuum energy distribution. The inflection probably stems from the fact that the UV continuum in these stars consists of two components: the emission from an optically thick gas with T<8000 K and the emission from a gas with a much higher temperature. The total luminosity of the hot component is much lower than that of the cool component, but the hot-gas radiation dominates at λ<1800 Å. Previously, other authors have drawn a similar conclusion for several young stars from low-resolution IUE spectra. However, we show that the short-wavelength continuum is determined from these spectra with large errors. We also show that, for three of the stars studied (BP Tau, GW Ori, and T Tau), the accretion-shock radiation cannot account for the observed dependence F _λ ^c (λ) in the ultraviolet. We argue that more than 90% of the emission continuum in BP Tau at λ>2000 Å originates not in the accretion shock but in the inner accretion disk. Previously, a similar conclusion was reached for six more classical T Tau stars. Therefore, we believe that the high-temperature continuum can be associated with the radiation from the disk chromosphere. However, it may well be that the stellar chromosphere is its source.  相似文献   

Comment on “The chemical variation of moldavite tektites: Simple mixing of terrestrial sediments” by Th. Meisel,J. M. Lange and U. Krähenbühl     

WOLF VON ENGELHARDT  J RG ARNDT 《Meteoritics & planetary science》1998,33(3):535-535

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Emission fluxes and atmospheric degradation of monoterpenes above a boreal forest: field measurements and modelling     

JÖRG SPANKE  ÜLLAR RANNIK  RENATE FORKEL  WALTER NIGGE  THORSTEN HOFFMANN 《Tellus. Series B, Chemical and physical meteorology》2001,53(4):406-422

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Studying Delta Dynamics by Space Photographs     

Kravtsova  V. I. 《Water Resources》2022,49(5):880-894

Water Resources - A review of the joint studies of the Chair of Land Hydrology and the Laboratory of Aerospace Methods, the Faculty of Geography, Moscow State University, on river delta dynamics...  相似文献   

Analysis of Forbush decreases during strong geomagnetic disturbances in March–April 2001     

M. V. Kravtsova  V. E. Sdobnov 《Astronomy Letters》2014,40(8):519-525

Using ground-based cosmic-ray (CR) observations on the worldwide network of neutron monitors, we have studied the variations in CR rigidity spectrum, anisotropy, and planetary system of geomagnetic cutoff rigidities during Forbush decreases in March-April 2001 by the global spectrographic method. By jointly analyzing ground-based and satellite measurements, we have determined the parameters of the CR rigidity spectrum that reflect the electromagnetic characteristics of the heliospheric fields in each hour of observations within the framework of the model of CR modulation by the heliosphere’s regular electromagnetic fields. The rigidity spectra of the variations and the relative changes in the intensity of CRs with rigidities of 4 and 10 GV in the solar-ecliptic geocentric coordinate system are presented in specific periods of the investigated events.  相似文献   

Surface typochemistry of hydrothermal pyrite: Electron spectroscopic and scanning probe microscopic data. II. Natural pyrite     

V. L. Tauson  R. G. Kravtsova  V. I. Grebenshchikova  E. E. Lustenberg  S. V. Lipko 《Geochemistry International》2009,47(3):231-243

Pyrite crystals from gold deposits of various genetic types (mesothermal and epithermal) were examined by techniques of x-ray photoelectron and Auger electron microscopy and by scanning probe microscopy. The results confirm a conclusion made in earlier hydrothermal experiments that nonautonomous phases (NP) of variable composition occur on the surface of pyrite crystals. These phases are localized within a layer of submicrometer (nanometer) thickness (up to ～0.5 μm) within which the typochemistry of pyrite surface is pronounced. The development of sulfate on the surface of pyrite crystals from epithermal Au-Ag deposits is a typochemical feature of the origin of their ore mineralization at low temperatures and shallow depths. Supergene conditions are characterized by the presence of an oxi-hydroxide or oxide film of FeIII, which morphologically differs from the layer of a pyrite-like NP. The composition and properties of the NPs are different for pyrite from mesothermal and epithermal deposits: they are close to those of a pyrrhotite-like NP discovered on synthetic hydrothermal pyrite and contain an additional sulfite anion for pyrite from the former type of deposits and are close to sulfide-disulfide ensembles with trivalent Fe for pyrite from the latter type of deposits. Trace elements, including precious metals, can be accommodated in such a phase via the stabilization of clusters with Fe³⁺ and SO ₄ ^2? in its structure. The instability of the crystallization process in epithermal environments may bring about the development of double-level nanostructure because of the structural transformation of vicinal surfaces into a set of ordered domains and the synthesis of nonautonomous “precursor” phases. Such systems can be stabilized via the excess dissolution of admixtures or the transition of the surface layer into another phase state.  相似文献   

Methodological Problems of Studying the Underwater Relief in the River Delta from Space Images (on the Example of Mapping the Shallows of the Yenisei River Delta)     

Kravtsova  V. I.  Vachnina  O. V.  Chalova  E. R. 《Water Resources》2021,48(4):474-484

Water Resources - Based on images from the Sentinel-2 satellite taken in 2017–2019, a map of shallows in the Yenisei delta was compiled. This paper highlighted the methodological problems...  相似文献