Geochronology of the Dovyren intrusive complex, northwestern Baikal area, Russia, in the Neoproterozoic

The paper reports newly obtained data on the geochronology of the Dovyren intrusive complex and associated metarhyolites of the Inyaptuk Formation in the Synnyr Range. The data were obtained by local LA-ICPMS analysis of zircons in samples. The U-Pb age of olivine-free gabbronorite from near the roof of the Yoko-Dovyren Massif is 730 ± 6 Ma (MSWD = 1.7, n = 33, three samples) is close to the estimated age of 731 ± 4 Ma (MSWD = 1.3, n = 56, five samples) of a 200-m-thick sill beneath the pluton. These data overlap the age of recrystallized hornfels found within the massif (“charnockitoid”, 723 ± 7 Ma, MSWD = 0.12, n = 10) and a dike of sulfidated gabbronorite below the bottom of the massif (725 ± 8 Ma, MSWD = 2.0, n = 15). The estimates are also consistent with the age of albite hornfels (721 ± 6 Ma, MSWD = 0.78, n = 12), which was produced in a low-temperature contact metamorphic facies of the host rocks. The average age of the Dovyren Complex is 728.4 ± 3.4 Ma (MSWD = 1.8, n = 99) based on data on the sill, near-roof gabbronorite, and “charnockitoid”) and is roughly 55 Ma older than the estimate of 673 ± 22 Ma (Sm-Nd; [13]). The U-Pb system of zircon in two quartz metaporphyre samples from the bottom portion of the Inyaptuk volcanic formation in the northeastern part of the Yoko-Dovyren Massif turns out to be disturbed. The scatter of the data points can be explained by the effect of two discrete events. The age of the first zircon population is then 729 ± 14 Ma (MSWD = 0.74, n = 8), and that of the second population is 667 ± 14 Ma (MSWD = 1.9, n = 13). The older value pertains to intrusive rocks of Dovyren, and the age of the “rejuvenated” zircon grains corresponds to the hydrothermal-metasomatic processes, which affected the whole volcano-plutonic sequence and involved the serpentinization of the hyperbasites. This is validated by the results of Rb-Sr isotopic studies with the partial acid leaching of two serpentinized peridotite samples from the Verblyud Sill. These studies date the overprinted processes at 659 ± 5 Ma (MSWD = 1.3, n = 3).     

Atmospheric circulation and storm events in the Black Sea and Caspian Sea

Extreme sea storms are dangerous and a potential source of damage. In this study, we examine storm events in the Black Sea and Caspian Sea, the atmosphere circulation patterns associated with the sea storm events, and their changes in the present (1961–2000) and future (2046–2065) climates. A calendar of storms for the present climate is derived from results of wave model SWAN (Simulating WAves Nearshore) experiments. On the basis of this calendar, a catalog of atmospheric sea level pressure (SLP) fields was prepared from the NCEP/NCAR reanalysis dataset for 1961–2000. The SLP fields were subjected to a pattern recognition algorithm which employed empirical orthogonal decomposition followed by cluster analysis. The NCEP/NCAR reanalysis data is used to evaluate the occurring circulation types (CTs) within the ECHAM5-MPI/OM Atmosphere and Ocean Global Circulation Model (AOGCM) for the period 1961–2000. Our analysis shows that the ECHAM5-MPI/OM model is capable of reproducing circulation patterns for the storm events. The occurrence of present and future ECHAM5-MPI/OM CTs is investigated. It is shown that storm CTs are expected to occur noticeably less frequently in the middle of the 21^st century.     

Estimation of air temperature reproduction quality by the MM5 model in the Urals in July

The quality estimation of diurnal air temperature course reproduction by the hydrodynamical MM5 model in the Urals in July is carried out by means of the comparison with the station observational data. The MM5 model reproduces the temperature maximums better than the minimums which are considerably overestimated by the model. The highest accuracy of air temperature reproduction is demonstrated by the model at 03:00, 06:00, 09:00, 12:00, and 24:00, whereas the lowest one, at 15:00, 18:00, and 21:00. The correlation coefficients between the model and actual data vary from 0.74 at 21:00 to 0.87 at 09:00 and 12:00. The autocorrelation functions computed for the actual and model data indicate that the MM5 model reproduces the temperature field with higher quality than the technique based on the inertial properties of the atmosphere.     

Ecological problems of development of the Ozyornoye lead and zinc deposit (Western Transbaikalia)

We outline the natural conditions of the area of the Ozyornoye deposit, the population and economy of the territory, the geological structure of the deposit, and the technological patterns of its development. We examine the sources of environmental impact, and the technical means of resolving this problem. Some ways to optimize the ecological situation in the area of development of the deposit are discussed.     

Mesoscale Atmospheric Modeling of Extreme Velocities over the Sea of Okhotsk and Sakhalin

A detailed modeling of meteorological parameters over the last 30 years (1985–2014) has been performed for the Sea of Okhotsk and Sakhalin regions in the frame of the COSMO-CLM regional mesometeorological nonhydrostatic atmospheric model. The downscaling technology is suggested and achieved with three consequent “nesting domains” (with 13.2-, 6.6-, and 2.2-km grid scales). The COSMO-CLM model reproduces (especially successfully on the 2.2-km grid scale) the extremes of wind velocity observed by meteorological stations well. Synoptic situations accompanied by extreme wind speeds are reproduced in detail.     

Level Variations in the Caspian Sea under Different Climate Conditions by the Data of Simulation under CMIP6 Project

Water Resources - Water balance components for the territory of the Volga basin and Caspian Sea water area have been analyzed using the results of climatic simulation under CMIP6 Project for...     

The Dovyren intrusive complex: Problems of petrology and Ni sulfide mineralization

This paper presents a review of petrological-geochemical studies at the Yoko-Dovyren Massif with an emphasis on relations between parameters of the parental magma, a model for the genesis of the lower contact zone, and the nature of Ni sulfide ore mineralization, including the evaluation of the possible ore potential. Arguments are presented in support of the conclusion that the Dovyren magma brought much intratelluric olivine of the composition Fo _85–87 into the chamber, and the composition of the initial melt corresponded to gabbronorite or moderately magnesian basite with no more than 10 wt % MgO. The probable temperature of the parental magma was approximately 1200–1250°C, and the sulfur solubility did not exceed 0.10–0.12 wt % (P = 1 kbar, WM buffer). The comparison of this estimate with the average S contents in the bottom plagioperidotites (0.12±0.06 wt %) indicates that the initial magma was saturated with a sulfide phase. For the first time the problem of the composition of contaminated dunites was formulated (these rocks occur in the Layered Series and contain more magnesian olivine Fo _87–92). The reason for the increase in the mg# of olivine is thought to be the partial melting and compaction of the original cumulates due to the infiltration of intercumulus melt enriched in volatile components. The volatiles were presumably provided by the thermal decomposition of carbonate xenoliths, a process that resulted in an increase in the CO₂ pressure and the transfer of calcite-magnesite components of carbonates into the melt. This follows from (1) the occurrence of magnesian skarn developing after carbonates, (2) high CaO contents in olivine form the contaminated dunite, (3) the appearance of olivine-bearing pyroxenites and wehrlites in the upper part of the dunite zone, (4) correlation between the olivine and chromite composition in the contaminated and uncontaminated dunites, (5) broad variations in the oxygen isotopic composition of olivine and plagioclase from rocks of the Layered Series, (6) experimental data on the dissolution of carbonates in alkali basalt melts, and (7) analogies with isotopic-geochemical characteristics of rocks from the Jinchuan ultramafic complex. Petrological implications of the interpretation of the Dovyren chamber are discussed with reference to closed and flow-through (during an initial stage) magmatic systems. A petrological-geological model is proposed for the genesis of the Synnyr-Dovyren volcanic-plutonic complex and related Ni sulfide ore mineralization. The potential resources of Cu-Ni sulfide ores in the plagioperidotites are evaluated with regard to the still-unexposed part of the massif.     

Evaluation of summer temperature and precipitation forecasts generated by the MM5 model over central European Russia

The results of the MM5 regional meteorological model are compared with the station data. The simulations are carried out for the central part of the East European Plain for summer with a horizontal grid resolution of 15 km (24 × 34 grid points) and 24 vertical σ-levels, the upper level corresponding to 100 hPa. The MM5 model reliably reproduces information at a spatial scale of about 100 km, systematically overestimating temperature by about 1.5°C and underestimating daily precipitation totals by about 1 mm. The distribution functions for model and observed temperatures coincide with the Gaussian distribution function. The precipitation distribution functions are rather similar and have a form of the χ²-distribution with one degree of freedom. Station and model temperature extremes generally coincide in time. Extremes of daily precipitation totals are slightly underestimated by MM5.     

International Conference on “Ultramafite-Mafite Complexes of Precambrian Fold Belts” held on the shore of Lake Baikal

Information on the International Conference “Ultramafite-Mafite Complexes of Precambrian Fold Belts,” which was held on September 6–9, 2006, in the Settlement of Enkhaluk in the Kabansky district of the Buryat Republic is presented. Brief contents of the contributions are also given.     

Analyzing the vortex as an integral formation: A case study for the blocking anticyclone of 2010

The peculiarities of blocking conditions and weather anomalies over the East European Plain in the summer of 2010 are considered using the EOF analysis and vorticity equation. The EOF analysis simulates the time series of the anticyclone as a whole using the principal modes of temporal variability. The vorticity equation is transformed into the specific form which enables assessing the contribution of different factors to the development and lasting existence of blocking conditions.