Том 478, № 2 (2018)

Complex modern micro- and spectroscopic methods for study of siderite concretions in the Lower Carboniferous terrigenous strata on the Kozhym River (Subpolar Urals) have shown that its formation was caused by destruction of clay minerals due to the activity of bacterial communities. The abundance of these bacteria was caused by gas–fluid seeps and bacterial methanogenesis processes in bottom deposits. In basins with normal marine fauna, this led to local desalination, hydrogen sulfide contamination, mass collapse of primary organisms, and the development of element-specific bacteria. The occurrence of these bacteria caused the formation of specific authigenic mineralization in the concretion of sideritic bacteriolites: the framboidal pyrite, sphalerite, galenite, barite, sulfoselenides, and tellurides.

The geochronological U–Pb study of shorlomite from igneous rocks of the alkali–ultramafic Afrikanda massif (Kola Peninsula) was performed. The results demonstrate the reliability of calcium garnet as a mineral for the U–Pb geochronology of a wide range of igneous rocks, i.e., carbonatite, syenite, foidolite, foidite, melilitolite, melilitite, lamprophyres, micaceous kimberlites, etc., and associated rare earth and trace elements (REE, Nb, Zr) mineralization.

U–Pb dating of the Torangalyk Complex (Northern Balkhash) yielded a Late Carboniferous age of 305 ± 2 Ma. Taking into account the previous data, a new scheme for Late Paleozoic granitic magmatism in this region has been proposed. It includes the Early Carboniferous granite–granodiorite Balkhash Complex, Late Carboniferous monzonite–granosyenite Kokdombak and Torangalyk complexes, and the Late Carboniferous–Early Permian granite–leucogranite Akchatau Complex.

The results of thermobaric geochemical study of ores of the Dvoinoye epithermal Au–Ag deposit are considered. Study of the fluid inclusions has shown that the ores were formed from low-salinity hydrothermal solutions with Na, Ka, and Mg chlorides and CO₂, HS^–, CH₄ trace fluxes at the time when the temperature dropped from 370 to 130°C. The results are compared with data obtained from the closely located Kupol and Sentyabr’skoye deposits.

This work presents new data on the composition of volcanics, developed within the Alazeya Plateau of the Kolyma–Indigirka fold area (Northeast Russia), which indicate essential differences in their composition and, accordingly, different geodynamic settings of the formation of rocks. The studied igneous rocks are subdivided into two groups. Volcanics of the first group of the Late Cretaceous age, which are represented by differentiated volcanic rock series (from andesitobasalts to dacites and rhyolites), were formed under island arc conditions in the continent–ocean transition zone. Volcanics of the second group are ascribed to the tholeiitic series and were formed under the other geodynamic setting, which is associated with the regime of extension and riftogenesis, manifested in the studied area probably at the later stage.

The Paleoarchean age (3.34 Ga) of subalkali granite magmatism first established for the Kukhtui uplift of the Okhotsk Massif suggests a formation time of the mature continental K-rich crust in this region as early as the Paleoarchean. According to the geological structural, mineralogical–geochemical, geochronological, and isotopic–geochemical data, the Kukhtui uplift can be considered as the most ancient Paleoarchean province in Russia: the ancient consolidation core of the sialic protocrust of the Okhotsk–Omolon Craton.

An extensive Middle Cretaceous orogenic belt of East Asia, which occupies the Okhotsk–Koryak–Western Kamchatka territory, encompasses thrust-and-fold structures. It formed over an interval of 130–110 Ma as a result of perioceanic accretion–obduction processes involving marine allochthonous complexes up to the Barremian inclusive, which experienced large amplitude displacements. Under the remote impact of subsequent (end of the Cretaceous and Cenozoic) perioceanic tectonic events, the primary structures of the Middle Cretaceous belt underwent compression-related superimposed deformations and fragmentation of allochthons with negligible displacement amplitudes. This led to the formation within the belt of a mosaic pattern of alternating fragments of neo-autochthons and allochthons bounded by young thrusts and strike–slip faults, often suggested as independent heterochronous terranes.

Using high-resolution analytical electron microscopy, heterogeneous fragments of cosmogenic substances, such as nickelphosphide Ni₃P and the unnamed intermetallide ZnAl₂, are detected for the first time for a large meteorite crater, the Zhamanshin circular structure. Due to the impossibility of simultaneous finding these phases in the same meteorite, an assumption is made on the cometary nature of the impactor of the Zhamanshin crater.

The Tamunyer deposit is a typical example of gold–sulfide mineralization located in the lower lithologic–stratigraphic unit (S₂–D₁) of the Auerbach volcanic–plutonic belt. The latter comprises island–arc andesitic volcano–sediments, volcanics, and comagmatic intrusive formations. Carbonates have demonstrated intermediate values of δ¹³C between marine limestone and mantle. The quartz δ¹⁸O is in the range of 15.3–17.2‰. The δ³⁴S of sulfides from the beresitized volcano-sedimentary rocks and ores varies widely from –7.5 to 12‰. The calculated isotope compositions of H₂O, CO₂, and H₂S of the ore-bearing fluid imply two major sources of matter contributing to ore genesis: local rocks and foreign fluid. The ore-bearing fluid was formed by interaction and isotope equilibration between a deep magmatic fluid and marine carbonates (W/R ~ 1), with the contribution of sulfur from the volcano-sedimentary rocks.

Geochemical study of water samples taken from the Malyi Mukulan and Bol’shoi Mukulan creeks and watercourses and trickling from the pile dike of tailing pond no. 3(1) of the Tyrnyauz tungsten–molybdenum plant has been carried out. Estimation of the degree of their polluting effect on the Baksan River was made.

Accessory wolframite with an extraordinarily high rhenium content (2.93–3.52%) in ongonite from the Badzhal area in the Far East is described. The capacity of tungsten isomorphic substitution with rhenium in wolframite is studied. The appearance of rhenium-bearing wolframite is caused by specific conditions of the crystallization of rare-metal granite magmas.

The results of analysis of more than 1300 new PKiKP/PcP amplitude ratios measured in Southeast Asia and South America at the epicentral distances of 3.2°–35.2° are presented. The density jump in the Eastern Hemisphere of the Earth’s inner core (IC) is 0.3 g/cm³, and it is 0.9 g/cm³ in the Western one. Taking the large discrepancy in the obtained estimates into consideration, maintenance of such large lateral variations in the mosaic properties of the IC reflecting surface requires considerable variations in the thermodynamic parameters (mostly temperature) of the inner–outer core transition. However, if the observed asymmetry in the density jump distribution is of a global character, the data presented support the translation model of the IC dynamics. This model implies IC crystallization in the Western Hemisphere and melting in the Eastern one, not vice versa, as suggested by another geodynamic model based on thermochemical convection in the outer core and the thermal balance of the core–mantle system.

This paper reports the heat flow calculations that were made on the basis of the temperature measurements in the boreholes at the Pavlovskoye deposit (Novaya Zemlya), the definition of the thermal conductivity of the rocks sampled from the boreholes, and the estimation of the radiogenic thermal generation in the drilling interval. This gives the first heat flow measurements in the archipelago. The structure of the heat flow in the Novaya Zemlya archipelago is compared with other fold belts of northern Asia.

In the present work, several results of repeated sounding of bottom ice gouging microrelief within the area of the underwater pipeline crossing of the Baydaratskaya Bay, Kara Sea, are presented. Based on the results of the monitoring, as well as the analysis of literature sources and modeling it has been established that under the conditions of climate warming and sea ice reduction, the zone of the most intensive ice gouging is shifted landwards, on shallower water areas.

The dynamics of the average annual temperature in the near-surface air and total annual precipitation in the South Urals are studied on the basis of observation data from ten meteorological stations of the Orenburg region, with the observation period being 90 years on average. By using wavelet transform and cross wavelet transform methods, the characteristic oscillation periods are revealed in the initial meteorological data series and correlations to the main climatic indices (AMO, NAO, and NAM) are calculated.

The first data on the concentrations, fluxes, and mineral and chemical compositions of aerosols from the near-water surface layer of the Caspian Sea are presented. It is shown that the aerosol fluxes onto the sea surface are comparable to the fluxes of a lithogenic substance in a water column. The mineral and chemical compositions of aerosols depend on the carrying air masses that pass through different regions. The coefficients of enrichment of aerosols with chemical elements relative to the upper lithosphere and their correlation relationships are studied.