Neotectonics and geodynamics of the Scythian Plate

Based on the results of structural-geomorphological analysis and tectonophysical modeling we identified an active geodynamic area in the basement of the Scythian Plate, which includes the Rostov salient, the northern part of the Stavropol uplift, Kuma-Tyulenev swell, and the eastern part of the Karpinskii swell and Astrakhan salient. This area is also characterized by maximal lineament densities, high heat flow, seismicity and the occurrence of hydrocarbon accumulations. It has been shown that the orientation of deformations within the Scythian Plate and Greater Caucasus orogen exhibits good correlation with those documented in the modern structural geometry of the Schythian Plate.     

Phase equilibria in the system lamprophyllite-nepheline

Experimental studies of the melting diagram for the lamprophyllite-nepheline system and data on the phases crystallizing in this system indicate that lamprophyllite incongruently melts with the origin of melt and titanium oxide. The maximum temperature at which nepheline and lamprophyllite can occur in equilibrium is estimated at 833 ± 6°C. Our pioneering data on lamprophyllite crystallization from melt prove that this mineral can be of magmatic genesis. The distribution coefficients between lamprophyllite and melt are evaluated for K (0.1–0.25), Mn (0.82–1.06), Fe (0.13–0.40), and Mg (0.82–1.5); and the Sr/Ba lamprophyllite/melt exchange coefficient is estimated at 1.8–3.7.     

Electron acceleration in the ionosphere of Io

A mechanism for the acceleration of electrons in the ionosphere of Io due to the moon's motion through the Jovian magnetic field and the presence of Io's ionosphere is considered. Attention is drawn to the important role of the anisotropic conductivity of the ionosphere, which results in the formation of a longitudinal (with respect to the planetary magnetic field) component of the charge-separation electric field. Owing to this anisotropy, the electric field induced by the motion of Io, E_i, produces in Io's ionosphere not only a Pedersen electrical current along E_i but also a Hall current that is approximately perpendicular to the moon's surface in the “upstream” and “downstream” parts of the ionosphere. However, this current cannot be closed through the surface, leading to the formation of a powerful charge-separation field in Io's ionosphere. This field has a component parallel to the magnetic field, with an amplitude comparable to that of the induced electric field. Electron runaway along the magnetic field is also considered, and the occurrence of “active longitudes” and preferred locations for the sources of decametric radio emission in the northern hemisphere of Jupiter are interpreted. The characteristic energies and fluxes of the accelerated electrons injected into Io's flux tube are estimated. The energy of these electron fluxes is sufficient to produce the electromagnetic radiation observed from Io's magnetic tube.     

Mathematical Modeling of Complex Reaches of Large River Channels

Mathematical models based on shallow water equations and on an equation of bed deformations are proposed to use in designing hydraulic structures and in channel straightening operations in large rivers. Specific examples of application of computer models are cited.     

Geochronology and Ore Mineralization of the Dzheltula Alkaline Massif (Aldan Shield,South Yakutia)

The Dzheltula alkaline massif is located in the Tyrkanda ore region of the Chara–Aldan metallogenic zone of the Aldan–Stanovy Shield (South Yakutia). The region contains separate placer gold objects, which are being explored at the present time, and ore-bearing Mesozoic alkaline intrusions, which are weakly studied due to their poor accessibility. The Dzheltula massif (DM) is the largest exposed multiple-ring intrusion within the Tyrkanda ore region; therefore, it is considered as a typical object for geological, petrological, geochronological, and metallogenic studies. The DM consists of five magmatic phases of syenite composition. ⁴⁰Ar–³⁹Ar dating has established that the crystallization age of the oldest phase, the leucocratic syenite porphyry (pulaskite), is 121.1 ± 1.3 Ma. The crystallization age of the cross-cutting phases represented by syenite–porphyry dikes (laurvikites and pulaskites) ranges from 120.1 ± 2 to 118.3 ± 2.1 Ma. The youngest phase of the massif, trachyte, crystallized at 115.5 ± 1.6 Ma. According to the mineralogical and geochemical studies, two types of ore mineralization, namely gold and uranium–thorium–rare-earth (U–Th–REE), are established within the DM. The gold mineralization was found in the quartz–chlorite–pyritized metasomatites. It is confined to the NNE- and NNW-trending fault zones and coincides with the strike of the syenite porphyry dike belt. Uranium–thorium–rare-earth mineralization has been established in the quartz–feldspathic metasomatites localized in the outer contact of the massif. The juxtaposition of mineralization of different types in some zones of the Dzheltula syenite massif significantly increases the ore potential of the studied object within the Tyrkanda ore region.     

A Molecular-Electronic Hydrophone for Low-Frequency Research of Ambient Noise in the World Ocean

Doklady Earth Sciences - This work is devoted to the problems of elaboration of the instrumental basis for low-frequency sensing of ambient noise of the ocean. The experimental data of testing of...     

Undamped Oscillations of Electric Current in Coronal Magnetic Loops and in Magnetic Loop Arcades

Geomagnetism and Aeronomy - The possibility of the existence of undamped oscillations of the electric current in coronal magnetic loops and loop arcades due to the presence of a photospheric...     

Evolution of Electric Current and Resistance in the Flare Loop in the Course of Loop Shrinkage

Geomagnetism and Aeronomy - Analysis of the phenomenon of the shrinkage of a coronal magnetic loop during the impulsive phase of a flare makes it possible to determine both the evolution of...     

Gyrosynchrotron Model of Microwave Sources Associated with the Magnetic Field Neutral Line

Geomagnetism and Aeronomy - The main properties of microwave radiation sources over the magnetic field neutral line, which follow from the assumption of a gyrosynchrotron mechanism of radio...     

Influence of the Solar Activity Cycle on the Gasdynamic Structureof the Heliospheric Interface

The effects of the 11 year solar activity cycle on the heliospheric plasma interface in the presence of neutral H-atoms have been investigated. Our calculations show that nonstationary processes of such kind lead to1) a decrease of the mean interstellar plasma density in the interface;2) a sequence of shocks and rarefaction waves moving from the heliopause (HP)to the bow shock (BS); 3) an expansion of the region between the BS and HP;4) the TS excursion along the upwind direction is within 30%of the mean solar distance. This revised version was published online in July 2006 with corrections to the Cover Date.