Volume 485, Nº 2 (2019)

The results of geological–geochemical studies of some Late Ordovician associations in the frame of the Minusinsk Trough with available geological and U–Pb, Rb–Sr, and K–Ar age dates are presented. The Late Ordovician volcanic rocks form a continuous igneous series, the basalts of which are different from Devonian basalts of the Minusinsk Trough in the lower TiO₂ content (≥ 1.7 wt %) and more fractionated REE pattern. These features should be considered the index characteristics of Late Ordovician rocks. Their compositions reflect processes of fractionation crystallization and mixing of trachibasaltic magmas with crustal melts. When taking into account the regional geological data, it is shown that magmatic activity at the Late Ordovician endogenic evolution stage in the northern part of the Altai–Sayan fold area was caused by the interaction of a mantle plume and the lithospheric mantle, which was metasomatically reworked and enriched in water during former subduction processes.

The age of hydrothermal metasomatic rocks of the Albyn gold ore deposit is shown to be 135–131 Ma. The Albyn deposit is one of the best-known ore gold deposits in the Eastern Asia. We assume that the formation of the deposit is associated with dislocations and metamorphism of volcanic-sedimentary sequences of the Mongol–Okhotsk Fold Belt.

Based on a study of pyrite from the Uzelga Cu–Zn volcanogenic massive sulfide (VMS) deposit (South Urals) the age of ore mineralization was first determined with the direct age dating method, based on the fraction of radiogenic helium, incorporated into the pyrite crystal lattice from submicron inclusions of U and Th minerals. Taking into account the measurement errors, the obtained age of 377 ± 8 Ma (MSWD = 1.2) is quite consistent with the independent age dates available for the ore mineralization (Late Eifelian–Early Givetian, 385–390 Ma).

This paper presents the results of U–Th–Pb geochronological study of detrital zircons from cement of the Jurassic conglomerates of the Strelka Depression extending in the sublatitudinal direction along the border between the southern margin of the Selenga-Stanovoy superterrane and the Mongol–Okhotsk fold belt. It has been shown that Paleoproterozoic and Neoarchean zircons overwhelmingly dominate in the conglomerate cement. This indicates that the main input of the material to the sedimentation basin was carried from the Southeast border of the North Asian craton (from the north in modern coordinates). In our opinion, the Strelka Depression formed after the completion of orogenic processes associated with the formation of the Mongol–Okhotsk structure.

The trace element composition of the Onello meteorite is analyzed in detail using SEM and LA-ICP-MS. The following Ni contents of minerals are determined (wt %): 23.0–25.4 in taenite, 5.8–8.8 in kamacite, 22–26 in schreibersite, 44–52 in nickelphosphide, 20.6–21.8 in allabogdanite, and 75–81 in awaruite. In the trace element content, the Onello meteorite corresponds to the IAB group of iron meteorites. Inside this group, it mostly matches the sHH subgroup (with high Au and Ni contents). The presence of allabogdanite in the meteorite indicates the high PT parameters of its formation: >8 GPa and 1000–1400°C. Thus, the formation of the Onello meteorite is related to impact metamorphism of a parental body of iron meteorites of the IAB group and vinonaites, in which a P- and Ni-rich area underwent melting and further crystallization.

Pyrite ores have been formed on the Earth from the Archean to the present. The most important component, sulfur, can be provided by the following three sources: igneous, sedimentary, and sulfates of seawater. Studies of contemporary hydrothermal systems of the seabed, which are considered to be the ore-generating mechanism responsible for the oldest pyrite deposits, have shown that magmatic sulfur and seawater sulfate make the major contribution to the total sulfur budget in ore formation [1–3]. The question of the influence of the simplest forms of life on the processes of ore formation, which is especially important and debatable for the Archaean deposits, is also widely discussed. However, our understanding of the processes occurring at the early stage of the Earth’s development is limited to a few available well-preserved geological samples, while the overwhelming majority of Archean rocks have experienced some degree of metamorphic changes.

The Raman spectroscopic studies of the lunar regolith from the samples of the Luna 24 automatic station resulted in recognition of the occurrence of three structural modifications of carbon: amorphous sp²-carbon, schungite-like carbon, and turbostratic graphite.

The causes of block formation, splitting, and twisting of crystals during their growth are considered. These phenomena are a result of joint action of the Punin effect (total autodeformation due to cross-sectorial heterometry that appears through nonuniform incorporation of impurities by the different faces of their parts) and the Rebinder effect (a sudden decrease in strength of the surface layer of a growing crystal covered by the mother liquor film, containing surfactants, by several times).

The reactions of 6Ag_(cr) + 3PdSe_2(cr) = 2Ag₂Se_(cr) + Ag₂Pd₃Se_4(cr) and 12Ag_(cr) + 5PtSe_2(cr) = 6Ag₂Se_(cr) + Pt₅Se_4(cr) were studied with the EMF method in a completely solid-state galvanic cell with an Ag ion-conducting solid electrolyte with overall gas space (argon under atmospheric pressure). The EMF vs. temperature dependencies were obtained in the temperature ranges of Т = 425–648 K and 501–713 K, respectively. Then, they were recalculated for gaseous Se fugacity in dependence on the temperature for nonvariant equilibriums of Ag₂Pd₃Se₄ (chrisstanleyite)–β-PdSe₂ (the phase, which transforms into verbeekite under low temperatures)–Ag₂Se (naumannite) and Pt₅Se₄ (luberoite)–PtSe₂ (sudovikovite): logf Se₂(gas) (Ag₂Pd₃Se₄/Ag₂Se/PdSe₂) = 7.710 ± 0.050 – 8.524 ± 0.026(1000/T), logfSe₂(gas) (Pt₅Se₄/PtSe₂) = 7.135 ± 0.027 – 12.274 ± 0.016(1000/T).

Abandoned lands formed in the place of former arable lands occupy considerable areas in the steppe zone and are a basic reserve for the restoration of the steppe biome in Russia. Taking into account the secondary steppe ecosystems developed in the place of the abandoned lands, the total carbon dioxide sink in the steppe zone of Russia can reach 92–121 Mt С per year. This is comparable to the СО₂ sink in the managed forests of the Russian Federarion (96 Mt/yr) and accounts for 10–20% of the total sink of СО₂ in the terrestrial ecosystems of Russia. To increase the sink potential on the territory of the Russian Federation, the natural and restored steppe ecosystems should be preserved.

The Yoko-Dovyren ultramafic–mafic layered intrusion includes the Baikal deposit of Cu–Ni sulfide ores with Pt–Pd mineralization in the bottom part, and “horizons” and pockets of low-sulfide ores with Pt–Pd mineralization at the upper levels of the section. The highest concentration of Pd, Pt, Au, Ag, Hg, and Cd, as well as the widest variability in the noble-metal minerals, is typical of the vein-like bodies of anorthosite and pegmatoid anorthosite in the upper part of the critical horizon at the boundary between troctolite and the overlying gabbronorite. Most of the noble-metal minerals are the postmagmatic pneumatolytic (fluid–metasomatic) phases. Among them are palladogermanide with 19.8 wt % Ge, paolovite with 8.1% Ge, and zvyagintsevite with 0.55% Ge. The composition of palladogermanide is Pd_2.03(Ge_0.80As_0.15Bi_0.02)_0.97; Ge is significantly replaced with As in this phase, which is typical of endogenic Ge minerals.

Kaula’s empirical rule has been known for more than 50 years: the coefficients of expansion over spherical harmonics for the fluctuations of the gravitational field and terrain of the planets decrease as the number of the harmonic squared. This was found for Venus, the Moon, Mars, the asteroid Vesta, and very small celestial bodies. The inverse-square line spectra were also found for various types of the Earth’s surface on a scale of up to a hundred kilometers. From this it follows that the spectra of the terrain slope angles are constant, i.e., “white noise.” Thus, they are δ-correlated horizontally. These are the assumptions under which the random walk laws were derived by A.N. Kolmogorov in 1934. Using them, the equation of the horizontal probability diffusion of the terrain with the linear coefficient of diffusion D is derived. Based on the empirical data, D = 1.3 ± 0.3 m for the Earth, while for Venus it is almost an order of magnitude less. The slopes resist the wind; the rock crumbles, and the water flows down the slopes as well. This consideration turns Kuala’s rule into the random walk laws (over terrain) developed by Kolmogorov in 1934.

Based on the results of satellite monitoring, the anomalies of spatiotemporal distributions of wildfire areas, as well as the volumes of caused emissions of carbon-containing trace gases (CO, CO₂) and aerosols (PM_2.5), for the territory of European Russia and Eastern and Central Europe from 2005 to 2018 are detected. It is found that, for 2005–2013, the annual areas of wildfires shrank for the territory of European Russia by almost a factor of 10, and the volumes of emissions of harmful gas traces into the atmosphere decreased by a factor of 7. However, starting from 2014, they were recorded to increase. The seasonal (spring and summer) maxima occurred in the distributions of the burned areas and the emission volumes in the time period under study. An anomalously large number of fire sources was recorded on the territory of Ukraine in 2014–2018 (70% of all fires in Eastern and Central Europe) where the specific density of fire sources, their relative areas, and the relative volumes of emissions increased by a factor of 3–5.7 compared to 2010–2013 and grew by a factor of 5–7.5 in August 2014–2018 compared to other territories of Eastern, Central Europe, and European Russia.

Based on multiyear current observations along 59.5° N in the Subpolar North Atlantic, multijet transport of arctic water along the eastern slope of Reykjanes Ridge producing the Iceland–Scotland overflow water (ISOW) in Iceland Basin is revealed. The main properties of the jet, as well as their contribution to deep water transport, are discussed.

A new quantitative approach to zoning of arid territories based on a new zoning climatic parameter (the sum of precipitation excesses over evaporation) and the soil-granulometric coefficient of moisture supply is proposed.