New paleomagnetic data on the Anabar Uplift and the Uchur-Maya region and their implications for the paleogeography and geological correlation of the Riphean of the Siberian Platform

The results of paleomagnetic studies of the reference sections of the Riphean and Late Proterozoic intrusive bodies of two remote areas of the Siberian Platform are presented. Within the limits of the Uchur-Maya region the sedimentary rocks of the Gonam, Omakhta, Ennin and Konder formations were studied; and the Riphean sedimentary rocks of the Burdur and Kotuykan formations on the northern and western slopes of the Anabar Uplift and, also, the Late Proterozoic intrusive complexes, located in the basins of the Fomich, Magan, Dzhogdzho and Kotuykan Rivers were studied. The paleomagnetic poles obtained in the course of this work and the present-day geochronological data give grounds to assume that: (1) the accumulation of the Riphean of the Anabar Uplift occurred after the formation of the Uchurskaya series of the Uchur-Maya region and was completed in approximately 1.5 Ga; (2) the Konder layers, compared according to the correlation pattern accepted at the present time [Semikhatov and Serebryakov, 1983] with the bottoms of the Totta formation, can be related to the appreciably more ancient stratigraphic level; (3) the intrusion of the studied intrusive bodies of the northern and western slopes of the Anabar Uplift occurred nonsimultaneously, although within close time intervals of approximately 1.5 Ga. The estimates of the kinematic parameters of the drift of the Siberian Platform within an interval of 1.7–1.0 Ga is carried out.     

Present-day stress-strain state in the upper crust of the Amurian lithosphere plate

Consideration is given to the issues of studying current geodynamic processes in the upper crust within the Amurian lithosphere plate. Present-day geodynamic processes in the lithospheric layer are shown to be located by different indicators that correspond to geological features of comparable scale and varying extension and are recognized by a set of investigative techniques. A variety of original data on vertical and horizontal motions of the surface is used to indicate the latest deformation processes. The best studied Trans-Baikal block was used as an example to analyse present-day geodynamics in the context of the tectonic flows conception. The present ideas concerning the stress-strained state of the upper part of the section within the Amurian plate have been refined based on non-uniformly scaled factors.     

On the role of integral feedbacks in stochastic climate models

Using a stochastic approach with zero-dimensional energy-balance models, we consider the problem of periodic climate changes and the influence of integral feedbacks on climate oscillations. Based on the resulting linear integral–differential stochastic equation, we calculate the spectrum of fluctuations of average surface-air temperature and determine its statistical properties. We analyze the influence of proper cycles of inertial units and “slow” nonstationarity on the fluctuation spectrum.     

Paleomagnetism of Mongolia

Most Lower Phanerozoic rocks of western Mongolia investigated were repeatedly remagnetized. They demonstrate a secondary magnetization component of normal and reversed polarity. The normal polarity components are related to Mesozoic rock remagnetization. The reversed polarity components were probably formed during the Carboniferous?Permian Superchron of reversed polarity. The analysis of the distribution of the reversed polarity component in the geological structure of Mongolia allows some zoning to be outlined with the defining regions of Mongolia characterized by insignificant rock defamations with intricate post-Permian dislocations and a region marked by rotation of large blocks around the horizontal axis (Khan Khukhei Range). It is assumed that Ordovician rock of western Mongolia contains a magnetization component close to the primary one. If the assumption is valid, the presumably northern paleolatitude derived from this direction corresponds to the interval of 14°?17°?20° (minimum?average?maximum, respectively).     

Magnetic signature of different vegetation species in polluted environment

Detailed magnetic study on vegetation samples from several strongly polluted and clean sites in Bulgaria is carried out in order to evaluate suitability of different species as passive dust collectors in magnetometry. From each location, available species among lichens, mosses, poplar leaves, dandelion, needles have been sampled. Magnetic susceptibility calculated on mass-specific basis shows wide variability between diamagnetic signal up to 846 × 10⁻⁸ m³/kg. Lichens and mosses are found to be the species, showing magnetic signals with the strongest contrast between clean and polluted environment. The main magnetic phase is magnetite-like according to the results from thermomagnetic analysis of susceptibility on magnetic extracts. Scanning electron microscopy (SEM) microphotographs reveal the presence of abundant particulate matter on vegetation surface both with anthropogenic (spherules) and lithogenic origin. Magnetic grain size deduced by the ratio of saturation remanent magnetization (SIRM) and mass-specific magnetic susceptibility (χ) and coercivities (B_c and B_cr) suggest that different species accumulate preferentially small SD-like grains from pollution emissions. Contrasting relationship of the ratio of anhysteretic remanent magnetization (ARM) and χ for polluted vs clean sites deduced by needles and lichens may be related to transformation of the accumulated dust particles within lichens’ tissue. This finding indicates that the exact species used as biological dust collector is of importance when studying spatial grain size distribution of magnetic dust particles. Pilot study on polycyclic aromatic hydrocarbons (PAH) content and its relation to magnetic parameters shows good correspondence between high levels of PAHs and high SIRM values for locations affected by non-ferrous industrial production.     

Photometric monitoring of the blazar 3C 345 for the period 1996–2006

We present the results of the blazar 3C 345 monitoring in Johnson‐Cousins BVRI bands for the period 1996–2006. We have collected 29 V and 43 R data points for this period; the BI light curves contain a few measurements only. The accuracy of our photometry is not better than 0.03 mag in the VR bands. The total amplitude of the variability obtained from our data is 2.06 mag in the V and 2.25 mag in the R band. 3C 345 showed periods of flaring activity during 1998/99 and 2001: a maximum of the blazar brightness was detected in 2001 February – 15.345 mag in the V and 14.944 mag in the R band. We confirm that during brighter stages 3C 345 becomes redder; for higher fluxes the colour index seems to be less dependent on the magnitude. The intra‐night monitoring of 3C 345 in three consecutive nights in 2001 August revealed no significant intra‐night variability; 3C 345 did not show evident flux changes over timescales of weeks around the period of the intra‐night monitoring. This result supports the existing facts that intra‐night variability is correlated with rapid flux changes rather than with specific flux levels. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental study of charge vertical transfer in surface air layer

The variability of air–earth electric currents in the lower 3-m air layer is analyzed in a complex with measurement data on the physical parameters that affect charge transfer in the atmosphere. Three types of air–earth current density profiles have been revealed during experimental observations in summer in Rostov region: (1) the current density decreases with an increase in the distance from the Earth’s surface and then stabilizes (nighttime conditions); (2) the current density increases with altitude up to 1 m and then decreases as altitude increases (day hours); (3) transient between types 1 and 2 that are observed in the morning and evening hours. The intensity of charge transfer in the surface air layer under the action of mechanical forces under different stratifications is estimated on the basis of data on altitude variations in the air–earth current density in view of the stationarity of electric processes and the constancy in the altitude of the total air–earth current density. Thermodynamic conditions are estimated with the use of wind velocity measurements and calculations of the turbulence factor and vertical component of the air temperature gradient.     

Some results of activities on the improvement of weather conditions over metropolises

Some results of activities on cloud seeding operations to modify the weather conditions over metropolises are given. The main objective of these activities was to dissipate the clouds and to decrease or to stop the precipitation on the territory under protection during the political, cultural, or sporting events. Up to 12 aircraft specially equipped with the measuring equipment needed to carry out the cloud seeding, with the Land-Aircraft-Land radio data transmission system, and with the cloud seeding means were used to fulfill the works on the weather modification. The liquid nitrogen, “dry ice”, silver iodide, and coarse-dispersion powder were used as the reagents for the cloud seeding. To control the aviation works and the results of the cloud seeding, the ground-based automated meteorological radar systems were used. The results of more than 40 large-scale operations on the improvement of weather conditions carried out since 1995 in different regions of Russia and near abroad indicate the efficiency of the methods and technical means of cloud seeding developed by the specialists of Roshydromet to modify the atmospheric precipitation.     

Effect of petrophysical properties and deformation on vertical zoning of metasomatic rocks in U-bearing volcanic structures: A case of the Strel’tsovka caldera,Transbaikal region

The development of vertical zoning of wall-rock metasomatic alteration is considered with the Mesozoic Strel’tsovka caldera as an example. This caldera hosts Russia’s largest uranium ore field. Metasomatic rocks with the participation of various phyllosilicates, carbonates, albite, and zeolites are widespread in the ore field. In the eastern block of the caldera, where the main uranium reserves are accommodated, hydromica metasomatic alteration gives way to beresitization with depth. Argillic alteration, which is typical of the western block, is replaced with hydromica and beresite alteration only at a significant depth. Postore argillic alteration is superposed on beresitized rocks in the lower part of the section. Two styles of vertical metasomatic zoning are caused by different modes of deformation in the western and eastern parts of the caldera. Variations of the most important petrophysical properties of host rocks—density, apparent porosity, velocities of P- and S-waves, dynamic Young’s modulus, and Poisson coefficient—have been determined by sonic testing of samples taken from different depths. It is suggested that downward migration of the brittle-ductile transition zone could have been a factor controlling facies diversity of metasomatic rocks. Such a migration was caused by a new phase of tectonothermal impact accompanied by an increase in the strain rate or by emplacement of a new portion of heated fluid. Transient subsidence of the brittle-ductile boundary increases the depth of the hydrodynamically open zone related to the Earth’s surface and accelerates percolation of cold meteoric water to a greater depth. As a result, the temperature of the hydrothermal solution falls down, increasing the vertical extent of argillic alteration. High-grade uranium mineralization is also localized more deeply than elsewhere.