Age of the Raygorodok Au-bearing Gabbro—Monzodiorite Massif (Northern Kazakhstan)

Accessory zircon from the polyphase Raygorodok stock (Northern Kazakhstan) has been dated by local U–Pb analysis (SIMS and LA-ICP-MS). This Au-bearing intrusion has been dated to 442–447 Ma, suggesting its emplacement at the very end of the Ordovician and Early Silurian, allowing the stock’s correlation with the Stepnyak Complex of small intrusions. Thus, control of small intrusions of the Stepnyak type over gold mineralization has been corroborated permitting their use as a regional prospecting characteristic.     

Studying intensive convection in Perm krai using the WRF model

Analyzed is a development of cloud convective system of short duration accompanied by severe thunderstorms, showers, squalls up to 22 m/s, and hail with the diameter reaching 20 mm and more in the afternoon on June 9, 2012 on the territory of Perm krai. An assessment of the convection development using the WRF-ARW model demonstrated that it simulates adequately the formation of convective systems on the territory of Perm krai. However, the zones of intensive precipitation coincide with its actual distribution not always. The Grell-Devenyi parameterization of convection gives the best results. The model does not simulate the hail formation processes: despite the fact of the development of this phenomenon on the territory of Perm krai on June 9, 2012, no hail formation was predicted by the model computations within the computational domain.     

Forecasting and prospecting criteria of Au-bearing weathering mantles in southern Siberia,Russia

The geological and genetic model of gold concentration at different stages of weathering has been developed on the basis of long-standing geological and geochemical research of Au-bearing weathering mantles in the main ore fields of Siberia. This model makes it possible to substantiate forecasting and prospecting criteria of gold deposits hosted in linear karst zones of weathering, to delineate prospective areas in southern Siberia, and to estimate their resource potential.     

Nanoparticles of noble metals in the supergene zone

Formation of noble metal nanoparticles is related to various geological processes in the supergene zone. Dispersed mineral phases appear during weathering of rocks with active participation of microorganisms, formation of soil, in aqueous medium and atmosphere. Invisible gold and other noble metals are incorporated into oxides, hydroxides, and sulfides, as well as in dispersed organic and inorganic carbonic matter. Sulfide minerals that occur in bedrocks and ores unaltered by exogenic processes and in cementation zone are among the main concentrators of noble metal nanoparticles. The ability of gold particles to disaggregate is well-known and creates problems in technological and analytical practice. When Au and PGE nanoparticles and clusters occur, these problems are augmented because of their unusual reactions and physicochemical properties. The studied gold, magnetite, titanomagnetite and pyrite microspherules from cementation zone and clay minerals of laterites in Republic of Guinea widen the knowledge of their abundance and inferred formation conditions, in particular, in the contemporary supergene zone. Morphology and composition of micrometer-sized Au mineral spherules were studied with SEM and laser microprobe. The newly formed segregations of secondary gold on the surface of its residual grains were also an object of investigation. The character of such overgrowths is the most indicative for nanoparticles. The newly formed Au particles provide evidence for redistribution of ultradispersed gold during weathering. There are serious prerequisites to state that microorganisms substantially control unusual nano-sized microspherical morphology of gold particles in the supergene zone. This is supported by experiments indicating active absorption of gold by microorganisms and direct evidence for participation of Ralstonia metallidurans bacteria in the formation of peculiar corroded bacteriomorphic surface of gold grains. In addition, the areas enriched in carbon and nitrogen have been detected with SEM on the surface of gold spherules from Guinea. Such organic compounds as serine, alanine, and glycine are identified on their surface with Raman spectroscopy. The experiments have been carried out and new data have been obtained indicating the role of micromycetes in concentration and distribution of noble metals in ferromanganese nodules of the World Ocean. Au and Pt were detected in the system with radioisotopes. It has been established that two forms of gold distribution develop within pseudomorphs of fungi colonies: (1) as pseudomorphic concentrates and (2) dispersed form unrelated to the colony structure. Inhomogeneities in distribution of dispersed platinum are manifested in the form of linear anomalies with elevated concentrations at the margins of the colonies.     

The Suzdal gold-sulfide deposit in the black shale of Eastern Kazakhstan

The Suzdal gold-sulfide deposit is situated in the northwestern part of the West Kalba gold belt in Eastern Kazakhstan and belongs to the genetic type of stringer-disseminated mineralized zones hosted in the Lower Carboniferous black-shale volcanic-carbonate-terrigenous sequences. Mineralization is controlled by the NE-trending Suzdal Fault. In the north, the deposit borders on the Early Triassic Semeytau volcanic-plutonic structure. Mineralization is superposed on the Late Paleozoic complex of metadolerite and quartz porphyry dikes. Ore deposition was a long-term process comprising four stages. The first stage was related to deposition of slightly auriferous pyrite syngenetic to host rocks. The second stage is characterized by formation of the first productive (with invisible gold) fine-acicular arsenopyrite mineralization accompanied by sericitization and localized in the tectonic zone. The stockwork ore with pocket-disseminated base-metal mineralization and free microscopic gold of the third stage is hosted in silicified rocks. The ore formation has been completed by quartz-stibnite veins superposed on all preceding types of mineralization. According to Ar/Ar dating of sericite, a chronological gap between the second and the third stages is estimated at 33 Ma. The deposit is an example of polygenetic and multistage mineralization.     

Hydrogen and calcium lines in solar prominence spectra

The solar prominence radiation spectrum has been simulated in close H and K lines of ionized calcium and hydrogen line H? convenient for processing in CCD observations. Equations of radiation transfer and statistical equilibrium in absence of LTE are solved for a model of homogeneous plane layer, taking into account the partial frequency redistribution for a 20-level continuum model of hydrogen atoms and a 5-level continuum model of calcium ions. The ratio of the integral intensities s = E(H Ca II)/E(H?) and t = E(K)/E(H) Ca II is calculated for a model grid (pressure 0.001 < P < 1.0 dyn/cm², temperature 4000 < T < 20000 K). The s(T, P) and t(T, P) constructed diagnostic charts for solar prominences are obtained for the first time with allowance for the influence of the Ly?? line on the ionization of Ca II ions.     

A GIS-based modeling of snow accumulation and melt processes in the Votkinsk reservoir basin

Coupled hydrological and atmospheric modeling is an efficient method for snowmelt runoff forecast in large basins. We use short-range precipitation forecasts of mesoscale atmospheric Weather Research and Forecasting (WRF) model combining them with ground-based and satellite observations for modeling snow accumulation and snowmelt processes in the Votkinsk reservoir basin (184,319 km²). The method is tested during three winter seasons (2012–2015). The MODIS-based vegetation map and leaf area index data are used to calculate the snowmelt intensity and snow evaporation in the studied basin. The GIS-based snow accumulation and snowmelt modeling provides a reliable and highly detailed spatial distribution for snow water equivalent (SWE) and snow-covered areas (SCA). The modelling results are validated by comparing actual and estimated SWE and SCA data. The actual SCA results are derived from MODIS satellite data. The algorithm for assessing the SCA by MODIS data (ATBD-MOD 10) has been adapted to a forest zone. In general, the proposed method provides satisfactory results for maximum SWE calculations. The calculation accuracy is slightly degraded during snowmelt periods. The SCA data is simulated with a higher reliability than the SWE data. The differences between the simulated and actual SWE may be explained by the overestimation of the WRF-simulated total precipitation and the unrepresentativeness of the SWE measurements (snow survey).     

Using fracture mechanics principles for calculating the pressurized structure lifetime by example of the propellant tank for the fourth stage of launch vehicle VEGA

The results of experimental and design-theoretical investigations on crack growth resistance of a propellant tank structure made of titanium alloy VT23 are presented.