Ionospheric response to the extreme solar burst of October 28, 2003

Using GPS and GLONASS navigation systems, instantaneous observations of solar burst effects on the Earth’s ionosphere are made. These observations are carried out for both Northern and Southern hemispheres, including the ionosphere at polar and equatorial latitudes. It is shown that the rate of total electron content (TEC) change is agrees well with the time profiles of solar bursts. An experimental dependence of the electron content gradient on the elevation angle is obtained.     

Middle Triassic age of metarhyolite of the Bondikha Formation,Argun Continental Massif,Central Asian Fold Belt

Research works carried out for the first time made it possible to determine the age of one of the key geological complexes in the Argun Continental Massif (Central Asian Fold Belt). It has been found that the metarhyolite of the Bondikha Formation is not Middle–Late Riphean, as previously thought, but is of Middle Triassic age (242 ± 6 Ma). Based upon the geochemical characteristics of the volcanics and regional geology of the Bondikha Formation, it can be assumed that they formed during one of the stages of subduction processes in the history of the Mongol–Okhotsk Fold Belt.     

Provenance sources of Upper Proterozoic and Lower Paleozoic clastic deposits of the Lesser Khingan terrane,Central Asian fold belt: U–Pb (LA–ICP–MS) geochronological results

Doklady Earth Sciences - The ages of detrital zircons from sandstones and silty sandstones from conditionally Upper Proterozoic–Cambrian rocks have been obtained for the first time. These...     

Late Paleozoic faults of the Altai region, Central Asia: tectonic pattern and model of formation

The present kinematic and dynamic analysis of large-scale strike-slip faults, which enabled the formation of a collage of Altai terranes as a result of two collisional events. The Late Devonian–Early Carboniferous collision of the Gondwana-derived Altai-Mongolian terrane and the Siberian continent resulted in the formation of the Charysh–Terekta system of dextral strike-slip faults and later the Kurai and Kuznetsk–Teletsk–Bashkauss sinistral strike-slip faults. The Late Carboniferous–Permian collision of the Siberian and Kazakhstan continents resulted in the formation of the Chara, Irtysh and North-East sinistral strike-slip zones. The age of deformation of both collisional events becomes younger toward the inner areas of the Siberian continent. In the same direction the amount of displacement of strike-slip faulting decreases from several thousand to several hundred kilometers. The width of the Late Paleozoic zone of deformation reaches 1500 km. These events deformed the accretion-collision continental margins and their primary paleogeographic pattern.     

Modelling of the lower ionosphere

The model of calculations of electron density profiles in D-region is suggested. The model includes four positive ions, four negative ions and electrons. The effective rate coefficients were received from detailed models of ionization-recombination cycle. The calculations, which were made, and the comparisons with experimental data (Ne-profiles and their variations, absorption of radiowaves) have showed, that in general the model described the basic features of D-region parameters.     

Age of Carbonates and Phosphorites in the Sedimentary Cover of the Tuva–Mongolian Microcontinent

The ages of the two main stages of carbonate cover formation within the Tuva–Mongolian microcontinent have been determined. The Pb–Pb age and Sr–chemostratigraphic characteristics of the carbonate rocks of the Irkutnaya, Agaringol, and Zabita formations, as well as of the Zabita Formation phosphorite, demonstrate that the first stage began in the Middle Riphean (Late Ectasian) at about 1290 Ma and the second stage started in the Early Vendian (Early Ediacaran) at 630–600 Ma. The accumulation of phosphorite deposits started in the Ediacaran at about 580 Ma.     

Nd and Pb Isotopic Composition of Granitoids in the Khangai Batholith as an Indicator of Crust-Forming Processes in the Terranes of the Central Asian Orogenic Belt

The Khangai batholith is one of the largest groups of granitoid plutons produced in Central Asia in the Late Permian–Early Triassic, at 270–240 Ma. The batholith occurs in the Khangai collage of Precambrian terranes, which include Early Precambrian crustal blocks (Dzabkhan and Tarbagatai) and Early to Late Neoproterozoic structures of the Songino block in their surroundings. The axial zone of this collage is overprinted by a basin filled with Devonian volcanic–siliceous rocks and Early to Middle Carboniferous terrigenous rocks. The isotopic parameters (Nd and Pb) of granitoids in the Khangai batholith indicate that the melts were derived from compositionally contrasting crustal sources and a single mantle one. The massifs hosted in the Precambrian blocks were produced with the involvement of lower crustal material, with various ages of the origin of the crust and its differentiation into upper and lower ones. The crust of the Tarbagatai and Dzabkhan blocks was produced in the Early Archean and was differentiated at the Archean–Proterozoic boundary. The crust of the Songino block was formed in the Paleoproterozoic and differentiated in the Early Neoproterozoic. According to the Pb and Nd isotopic parameters of granitoids in the Khangai Basin, the regional continental crust was close to the juvenile one, i.e., the continental crust of the Khangai Basin had still not been differentiated by the time when the Khangai batholith was produced. A single mantle source was involved in the origin of the melts of granitoids of the Khangai batholith in various tectonic blocks. The evolution of the Pb isotopic composition of this sources is consistent with the Stacey–Kramers model at µ = 9.5. This source can be identified with the enriched mantle, which has a higher U/Pb ratio than the depleted mantle and lower ε_Nd(T) of 0 to +2.     

Determination of the photoelectron current density based on comparison between IESP-2 and KM-7 probe measurements of the interball-2 satellite potential relative to plasma

We propose a technique for determining the photoelectron current density based on comparison between simultaneous IESP-2 (electric field meter) and KM-7 (electron temperature sensor) probe measurements of the Interball-2 satellite potential relative to the plasma. We have analyzed the data obtained from ～350 orbital segments in the auroral zone of the magnetosphere at altitudes of 2–3 Earth’s radii from October 1996 to March 1998, i.e., in the period of low solar activity at the beginning of solar cycle 23. The photoelectron current density onboard Inteball-2 has been found to be within the range 1.8–3.6 nA cm^?2.     

Spectral observations using a BTA telescope of chemically peculiar stars in the spectral region near the Li I (6708 Å) resonance doublet

New spectral observations of chemically peculiar (CP) magnetic stars were obtained using an NES echelle spectrometer with a BTA telescope in the Special Astrophysical Observatory (Russian Academy of Sciences). Several stars were shown to have anomalous Li abundances. Testing and monitoring the stars with Doppler shifts Vsini > 10 km/s indicated that the lithium 6708 Å line was variable in the spectra of some roaAP-CP stars. To distinguish variable features in the spectra, the dispersogram technique was used. The most peculiar among the stars studied is HD 12098. The strong and variable lithium 6708 Å line was detected in the spectrum of this star. The star has been shown to have greatly different lithium abundances in two rotation phases corresponding to opposite surface areas. As mentioned earlier, a similar behavior of the Li blend was found in the spectra of HD 83368 and HD 60435 which have lithium spots on their surface. Spectral observations of slowly rotating CP stars with the Doppler shifts Vsini < 10 km/s revealed the strong and nonvariable lithium 6708 Å line in the spectra of these stars. Quantitative spectral analysis using the Li I 6708 Å resonance doublet and the Li I 6103 Å line shows the lithium abundance, as determined by the 6103 Å line, to be somewhat greater than that determined by the 6708 Å line. A higher ratio of ⁶Li/⁷Li amounting to ～0.3–0.5 was found in these stars. ⁶Li production is assumed to be due to spallation reactions on the surface of magnetic CP stars; this isotope ratio remained in strong magnetic fields.     

New data on the stratigraphy,volcanism, and zeolite mineralization of the Cenozoic Vanchinskaya depression in primorye

This paper presents the results of studying the Cenozoic volcanogenic-sedimentary cover of the Vanchinskaya depression of Sikhote Alin. It was established that, in terms of the taxonomic composition of the fossil plants, the basal part of the Cenozoic section is attributed to the Paleocene, while the overlaying coal-bearing sequence, to the Early Eocene. The geochronological (K-Ar) dating showed that the volcanic rocks intruding and overlaying the coal-bearing deposits are Middle Eocene in age: rhyolites—44.7 ± 1.0; trachyandesites—43.7 ± 1.4 Ma. The petrographic and geochemical characteristics of the volcanic and volcanogenic-sedimentary rocks and related zeolitites are described. The zeolitized rocks containing plant detritus differ in their extremely high contents of Y and HREE. The zeolitization of the volcanic glass in tuffs, tuffites, and perlites was caused by hydrothermal solutions that ascended along NW fault zones from the subsurface magmatic chamber.