Том 470, № 1 (2016)

Experimental data on residual oil mobilization in laboratory simulation of oil displacement by water demonstrate the impact of the scale effect on this process reflected in the value of residual oil mobilization and displacement thresholds. It is established that residual oil saturation decreases with an increase in the model size used. It is shown that the sizes of clusters of the trapped oil phase correlate with the size of the laboratory model.

The data presented introduce substantial changes into Quaternary stratigraphy, paleogeography, and the geological history of the Altai Mountains. The purpose of this investigation was thorough study of block accumulations in the Chuya and Katun river valleys. The new data shed light on the structure of these deposits, their composition, the geomorphological and stratigraphic position, and the morphology of blocks. The revealed morphological features of individual blocks imply their glacial origin.

Corundum-bearing rocks are described for the first time in the Kandalaksha structure of the Lapland granulite belt. Corundum is confined to rocks of two types: metagabbro‒anorthosites constituting lenses among metaanarthosites of the Kandalaksha massif and basic granulites. Corundum crystals (up to 200 μm long) occur in plagioclase and garnet and differ from each other depending on the host mineral, which serves as evidence against their xenogenic nature. Some corundum crystals exhibit an axial zone, which may indicate their crystallization from the gaseous phase. Corundum-bearing rocks are accompanied by piclogites (pyroxene‒garnet varieties with olivine). Piclogites and their minerals (clinopyroxene, garnet) are characterized by a positive Eu anomaly, which implies rock reworking by fluids during corundum formation, when deep-seated complexes were subjected to exhumation.

The melting of two basic granite varieties in the Voznesenka Complex such as Yaroslavka biotite granite and Voznesenka Li–F granite was subject to experimental studies to analyze and to compare the conditions of their physicochemical formation. The experiments were conducted at 550–700°C and 50–500 MPa in pure water and in 0.1 and 1 m HF aqueous fluorine-bearing solutions. The melting temperature of Voznesenka Li–F granites was 60–70°C lower than that of Yaroslavka biotite granites. The temperature decreased by almost 100°C from the completion of biotite granite crystallization to the completion of Li–F granite crystallization.

Pyrrhotite ores forming the hydrothermal vents of the Hydrothermal Hills in the Southern Trough of the Guaymas depression were studied. A series of features pointing to the occurrence of surface and buried sulfide deposits of pyrrhotite mineralization was revealed: the presence of pyrrhotite associations to hydrocarbons of oil series; low concentrations of Cu, Zn, and Pb; the enrichment of sulfur of pyrrhotite and hydrogen sulfide of hydrothermal solutions in heavy ³⁴S isotope by 5–7%; and the heavy isotope composition of carbon in naphthoid compounds. The results obtained allow one to suggest searching for large sulfide deposits at active rifts of high spreading and sedimentation rates, i.e., at near-continental rifts of the humid zone of avalanche sedimentation.

Using techniques of microprobe analysis and Raman microspectroscopy, a study of the composition, structure, and age of high-uranium zircon from the Sharatash intrusion pegmatite was performed. The presence of a number of zones in crystals having different physicochemical characteristics has been revealed. The Id-e zones affected by a radiation dose of (30–130) × 10¹⁸ α-dec/g were completely amorphized, and their chemical isochron age was estimated at 311.4 ± 7.1 Ma: this is interpreted as the time of zircon formation in the pegmatite. The age of uraninite coupled with zircon is 317.1 ± 2.3 Ma. These dating results clarify the formation time of the final phase (pegmatite) of the Shartash intrusion and determine the upper age limit of hydrothermal gold mineralization (Berezovsk deposit) associated with the granite massif.

Based on measurements of the concentrations of C, N, P, and chlorophyll-a, as well as on palynological analysis of the core Vdr 2011 of peaty sediments from the Vydrinaya River along the southern coast of Lake Baikal, the geochemical characteristics of eutrophy were compared to pollen indices of changes in the environment and the mode of marsh ecosystem transformations into various trophic states was specified. It was shown that geochemical parameters of the changes in the environment may be considered as the characteristics of trophic conditions in ecosystems in the course of paleo-reconstructions.

The first find of srilankite (very rare Zr and Ti oxide, Ti₂ZrO₆) in the Urals and the third find in Russia is reported. Srilankite forms very small (0.5–20 μm) inclusions in some rutile grains. These minerals are observed in the rare rock variety, corundum-bearing spinel–saphirine hornblendite forming a block in serpentinized amphibolizied peridotite of the Ilmeny–Vishnevogorsk Complex, near the village of Taiginka, Chelyabinsk oblast. Srilankite has not been observed in such an association yet. The composition of the host rock provides evidence for its deep (the lowermost crust of the Earth) origin. Srilankites of the Urals are distinguished from all others by the high concentrations of UO₂, ThO₂, HfO₂, and Nb₂O₅, which provides additional evidence for their crustal origin. Srilankite may indicate high-temperature and high-pressure conditions of rock formation.

The first study of the pyrite composition from gold deposit in the Urals by the LA-ICP-MS method has been carried out. In the pyrite high contents of Au (up to 49 ppm), Ag (105 ppm), and other micronutrients (As (417 ppm), Ag (105 ppm), Co (2825 ppm), Ni (75 ppm), Cu (1442 ppm), and Zn (19 ppm)) were detected. Furthermore, an increase in the concentrations of trace elements from early to later generations of pyrite (from Py-1 to Py-3) Au, Ag, Te, Sn, Te, and Bi and depletion of Co, As, and Ni have been revealed. Gold is mainly concentrated in the pyrite of the second generation (Py-2) and occurs mostly as an “invisible” form with prevalence of nano-sized particles of native Au, similar in composition to electrum AuAg, as well as Au- and Au–Ag tellurides. The presence in the pyrite of admixtures of Cu, Co, Ni, Pb, As, and Te, possibly favors the entrance of Au into it (up to 5–50 ppm), while in common pyrite, poor in the mentioned impurities, the gold content is <1 ppm.

Based on study of the Middle Paleozoic (Hercynian) structures of the Central Asian Fold Belt located in Southwest Mongolia, the problem of the sources of juvenile crust growth registered in the Pb isotope composition of postaccretional granitoids is considered. Our study shows that the Pb isotope system of Late Paleozoic granitoids from the Hercynides of the Central Asian Fold Belt provides evidence for the juvenile nature of the continental crust in this region. The evolution of the Pb isotope composition in the Hercynides of Mongolia corresponds to the model parameter μ = 9.25, according to the Stacey–Kramers twostage model. The juvenile source of the Hercynian crust should be characterized by a lower μ value. In addition, according to the Stacey–Kramers two-stage model, the Th/U value in this crust is 3.58.

We analyze experimental data collected in Vityaz Bay of the Sea of Japan during study of the peculiarities of spreading of hydroacoustic waves over a shelf with decreasing depth. We found that the waves propagate over a shelf with depths greater than half of the hydroacoustic wave according to the law of cylindrical divergence with least losses of the wave energy. If the depths are shallower than half of the hydroacoustic wave, they spread along the water-bottom boundary as Rayleigh waves of decaying and undamped types with significant absorption of the wave energy by the bottom.

The area of investigation was subject to multifactor analysis of the relationship between the maximum amount of mudflow solid sediments (W) and parameters such as the mudflow basin area (S), average channel slope (α), and mudflow channel length (L). They were used to obtain analytical expressions in order to approximate the W(S, L, α) relation based on the mudflow genesis and source height. Statistical data on mudflow manifestations in different basins in the North Caucasus covering more than fifty years were used to obtain the analytical expressions in order to assess the maximum volume of mudflow solid sediments.

Two major arrangements describing the oil-by-water displacement process, i.e., Muskat’s model without taking into account the surface tension on the free boundary and the Buckley–Leverett model based on the surface tension, are considered. These arrangements were subject to theoretical and numerical study, which made it possible to uncover their self-contradictoriness. The focus was on construction of a numerical solution at the microlevel using the direct method with pressure correction.