Determination of the isotopic composition of molybdenum in the bottom sediments of freshwater basins

This paper presents the results of measurements of the Mo isotopic composition in the bottom sediments (BS) of freshwater basins. Mo isotopic ratios were measured using a multicollector inductively coupled plasma mass spectrometer (MC ICP MS). Efficient methods were used in this study for Mo separation from the elements of the sample matrix and correction for instrumental mass discrimination. This allowed us to achieve a high accuracy of 0.06, 0.08, and 0.14‰ (2 σ) for the measurement of ⁹⁷Mo/⁹⁵Mo, ⁹⁸Mo/⁹⁵Mo, and ¹⁰⁰Mo/⁹⁵Mo, respectively. The range of variations in Mo isotope ratios observed in the collected BS columns was ～2.2‰ in terms of δ⁹⁷Mo/⁹⁵Mo. The results obtained here suggest that geochemical processes occurring during Mo migration with land water can change the isotopic composition of Mo. It is pointed out that the potential use of Mo isotopic systematics for reconstructions of redox conditions in seawater over the geologic past requires the quantification of isotopic effects of Mo accompanying its migration on land and the extent of possible variations in the isotopic composition of Mo entering the ocean.     

Early Cretaceous volcanic rocks and Early Cenozoic extrusions of Cape Mary, Schmidt Peninsula, north Sakhalin: Geochemical study

The Early Cretaceous volcanic rocks of the Mariisky sequence and Early Cenozoic extrusive-vent rocks of Cape Mary are exposed at the northwestern extremity of Schmidt Peninsula, north Sakhalin. In chemical composition, all the rocks are subdivided into four groups. Three groups include the volcanic rocks of the Mariisky sequence, which consists, from bottom to top, of calc-alkaline rocks, transitional calc-alkaline-tholeiite rocks, and incompatible element-depleted tholeiites. These rocks show subduction geochemical signatures and are considered as a fragment of the Moneron-Samarga island arc system. Trace-element modeling indicates their derivation through successive melting of garnet-bearing mantle and garnet-free shallower mantle sources containing amphibole; pyroxene; and, possibly, spinel. The mixed subduction and within-plate characteristics of the extrusive vent rocks of Cape Mary attest to their formation in a transform continental margin setting.     

Catalog of Supermassive Black Holes for Interferometric Observations

The paper presents a catalog of supermassive black holes (SMBHs) sharpened for interferometric observations at millimeter and submillimeter wavelengths, based on open sources. The catalog includes the object’s name, coordinates, angular size, and mass, the angular size of the gravitational radius of the SMBH, and the integrated radio flux associated with the radiosource concluding the SMBH at 20?900 GHz, planned for the Event Horizon Telescope, the future space mission Millimetron, and others. The catalog is intended for use during planning of interferometric observations of SMBH shadows.

     

Pollutant Migration in Water Bodies in Mining Regions (Based on Data on Apatite Deposits)

Variations in the key indices of the chemical composition of surface waters are studied in a region where these waters are polluted by mining plant wastes. The forms of metals migration and their distribution in the bottom deposits of watercourses are examined. The possible steps for reducing the pollution of water in a watercourse are discussed.     

Periodicity of copper accumulation in the Earth’s sedimentary shell

Physicochemical conditions of the migration and concentration of Cu in sedimentary rock, specific features of the formation of large and unique deposits of cupriferous sandstones and shales, distribution of copper deposits in the stratigraphic scale, and causes responsible for the reduction of Cu accumulation from Proterozoic to Cenozoic are considered. Genetic link of cupriferous sandstones and shales with arid red molassic rocks is shown. Conditions and periodicity of formation of the ore-generating red rocks are considered. An explanation for periodicity of maximum Cu accumulation in the Earth’s history is proposed.     

Current status of models with hot and cold dark matter

An analysis of a five-parameter family of cosmological models in a spatially flat Friedmann Universe with a zero Λ term is presented. The five parameters are (1) σ₈, the dispersion of the mass fluctuations in a sphere with radius 8h ^?1 Mpc, where h=H ₀/100 km s^?1 Mpc^?1 and H ₀ is the Hubble constant; (2) n, the slope of the density-perturbation spectrum; (3) Ω_v, the normalized energy density of hot dark matter; (4) Ω_b, the baryon density; and (5) h, the normalized Hubble constant. The density of cold dark matter is determined from the condition Ω _cdm >1?Ω_v?Ω _b . Analysis of the models is based on comparison of computational results with observational data for: (1) the number density and mass function of galaxy clusters (a so-called Press-Schechter formalism) and (2) the cosmic microwave background anisotropy. The first method enabled us to determine the value σ₈=0.52±0.01 with high accuracy. Using the resulting normalization of the density-perturbation spectrum, we calculated a model for the anisotropy of the cosmic microwave background radiation on large scales (l?10, where l is the harmonic number) and the required contribution of cosmological gravitational waves, characterized by the parameter T/S. The restrictions on T/S become weaker as Ω_v increases. Nevertheless, even when Ω_v≤0.4, models with h+n≥1.5 require a considerable contribution from gravitational waves: T/S?0.3. On the other hand, in models with Ω_v≤0.4 and a scale-invariant density-perturbation spectrum (n=1), we find T/S ?10(h?0.47). The minimization of T/S is possible only for the family of models with red spectra (n<1) and small h (<0.6). The value of Ω_v is determined most accurately by the data onΔT/T near the first acoustic peak (l?200). By imposing a general restriction on the amplitude of gravitational waves T/S∈[0, 3] and taking into account the available observational data on the amplitude of the acoustic peak of Sakharov oscillations, ranges of possible values n and Ω_v are derived. If the baryon number is constrained by nucleosynthesis data, the models under consideration can have both moderately red and blue power spectra n∈[0.9, 1.2] with a rather high concentration of hot particles Ω_v∈[0.2,0.4]. The conditions that n<0.9 and/or Ω_v<0.2 decrease the relative amplitude of the acoustic peak by over 30% compared to its value in the standard cold-dark-matter (CDM) model normalized using COBE data.     

Some aspects of the problem of geochemical methods of prospecting for concealed mineralization

This paper describes a number of different geochemical approaches to the search for concealed ore deposits.The first approach discussed is a broad one that relates mineralization to the types of rock that may occur in a region. Attention is focussed on hydrothermal deposits and their association with specific types of igneous rocks and their differentiation trends.A second considers the control of the structure and physico-chemical properties of the host rocks on the localization of ore bodies. A number of factors, such as effective and total porosity and the brittleness of rocks also plays an important role in determining the nature and extent of dispersion haloes of the elements around ore deposits.In some instances it is possible to predict the presence of ore bodies at depth from the type of composition of metasomatized rocks that occur at the surface.The use of mercury and fluorine in the search for concealed deposits has been given detailed consideration. Methods based on fluorine may be effective in the discovery of skarn, greisen, hydrothermal and rare metal deposits. When using the fluorine content of waters from a taiga-permafrost terrain, it is important to consider the effect of the organic content of the water.In searching for Cu-Ni deposits of the Noril'sk type it is suggested that intrusive complexes characterized by high degrees of differentiation and containing picritic and taxitic facies enriched in Mg, Ni and Co and depleted in alkalis are the most prospective. Ore deposits of this type may have dispersion haloes of Ag, Bi, Zn and Pb which are associated with ore-controlling faults. Magnesian and calcareous skarns, feldspathic and serpentine-chlorite-prehnite rocks may form broad contact haloes with ore-bearing intrusions.The use of gases in prospecting for Cu-Mo deposits in Central Kazakhstan have been investigated with positive results. Gas surveys carried out in conjunction with geophysical methods makes it possible to distinguish zones of Cu-Mo mineralization from zones containing pyrite and carbonaceous material, all of which give similar geophysical responses.The occurrences of uranium in aquifers on the flanks of artesian basins within arid regions is used as an example of the use of geochemical zonation in prospecting. The same approach may be used in prospecting for copper-bearing sandstones.     

Dislocations of the cretaceous and cenozoic complexes of the northern part of the West Sakhalin Terrane

The contemporary structure of the West Sakhalin Terrane started to form in the Pleistocene and the process of its formation continues up to now in a setting of ENE (60°–90°) shortening. Evidence of the preceding NE (30°–45°) compression was revealed during the study. This compression prevailed in the Eocene–Pliocene. Under the settings of NE (30°–45°) compression, dextral displacements occurred along the West Sakhalin and Tym’–Poronai fault systems, bounding the West Sakhalin Terrane.     

Strontium Migration in Groundwater of Fluvioglacial Sediments in the Khibiny Massif

The regularities of Sr absorption by different Quaternary fluvioglacial sediments, containing groundwater within the Khibiny massif, have been studied. The studied sediments have been shown to adsorb Sr as a result of the cation exchange and complexing on the solid phase surface, which is responsible for the absorbing capacity of the sediments in the wide range of natural water pH. The base exchange capacity of Sr has been established to largely depend on the concentration of the macrocomponents (Ca²⁺ and Mg²⁺) in the groundwater. It has been noted that the migration mobility of Sr is low under the conditions of almost neutral water typical of the soil horizon in the studied area.