The fauna of the Aral Sea in 1989. 1. The benthos

The benthos of the Small and Large Aral Sea was investigated in 1989. OnlyNereis diversicolor, Syndosmya segmentum, Cerastoderma isthmicum, Caspiohydrobia spp., Chironomidae andPalaemon elegans occurred in the Small Sea. In the Large Sea, the benthos was similar, but Chironomidae were absent andRhithropanopeus harrisii was present.     

Observations of the flux of very-high-energy gamma rays from the blazar 3C 66A

Measurements of the flux of very-high-energy (>1 TeV) gamma rays from the blazar 3C 66A obtained over four years are presented. The mean flux over the four-year period was (2.8±0.4)×10^?11 cm^?2 s^?1. There is a correlation between the season-averaged flux of very-high-energy gamma rays and the observed optical radiation.     

Compositions of magmas,formation conditions,and genesis of carbonate-bearing ijolites and carbonatites of the Belaya Zima alkaline carbonatite complex,eastern Sayan

Based on the investigation of melt inclusions using electron and ion microprobe analysis, we estimated the composition, evolution, and formation conditions of magmas responsible for the calcite-bearing ijolites and carbonatites of the Belaya Zima alkaline carbonatite complex (eastern Sayan, Russia). Primary melt and coexisting crystalline inclusions were found in the nepheline and calcite of these rocks. Diopside, amphibole (?), perovskite, potassium feldspar, apatite, calcite, pyrrhotite, and titanomagnetite were identified among the crystalline inclusions. The melt inclusions in nepheline from the ijolites are completely crystallized. The crystalline daughter phases of these inclusions are diopside, phlogopite, apatite, calcite, magnetite, and cuspidine. During thermometric experiments with melt inclusions in nepheline, the complete homogenization of the inclusions was attained through the dissolution of a gas bubble at temperatures of 1120–1130°C. The chemical analysis of glasses from the homogenized melt inclusions in nepheline of the ijolites revealed significant variations in the content of components: from 36 to 48 wt % SiO₂, from 9 to 21 wt % Al₂O₃, from 8 to 25 wt % CaO, and from 0.6 to 7 wt % MgO. All the melts show very high contents of alkalis, especially sodium. According to the results of ion microprobe analysis, the average content of water in the melts is no higher than a few tenths of a percent. The most salient feature of the melt inclusions is the extremely high content of Nb and Zr. The glasses of melt inclusions are also enriched in Ta, Th, and light rare earth elements but depleted in Ti and Hf. Primary melt inclusions in calcite from the carbonatites contain a colorless glass and daughter phlogopite, garnet, and diopside. The silicate glass from the melt inclusions in calcite of the carbonatite is chemically similar to the glasses of homogenized melt inclusions in nepheline from the ijolites. An important feature of melt inclusions in calcite of the carbonatites is the presence in the glass of carbonate globules corresponding to calcite in composition. The investigation of melt inclusions in minerals of the ijolites and carbonatites and the analysis of the alkaline and ore-bearing rocks of the Belaya Zima Massif provided evidence for the contribution of crystallization differentiation and silicate-carbonate liquid immiscibility to the formation of these rocks. Using the obtained trace-element compositions of glasses of homogenized melt inclusions and various alkaline rocks and carbonatites, we determined to a first approximation the compositions of mantle sources responsible for the formation of the rock association of the Belaya Zima alkaline-carbonatite complex. The alkaline rocks and carbonatites were derived from the depleted mantle affected by extensive metasomatism. It is supposed that carbonate melts enriched in sodium and calcium were the main agents of mantle metasomatism.     

Model of the Deep Structure of the Elbrus Volcano in the Light of New Geophysical Data

A geophysical section by the method of microseismic sounding is obtained along the profile that completely crosses the Elbrus volcano in the area of its eastern summit. The peculiarities of the deep structure and edifice of the Elbrus volcano are revealed.

     

Albite Metasomatic Rocks and Thorium Mineralization in Uranium Deposits of the Volcanogenic Type (Example of the Streltsovka Ore Field,East Transbaikalia)

Doklady Earth Sciences - The causes of metasomatic albitization of host rocks and the formation of the accompanying thorium mineralization in uranium deposits of the Streltsovka ore field located...     

Sunspot Activity and Coronal Holes during the Declining Phase of Cycle 24

Geomagnetism and Aeronomy - The dynamics of coronal holes (CHs) during the declining phase of solar cycle 24 is studied based on observational data from the Atmospheric Imaging Assembly (AIA), the...     

Changes in Water Quality in the Bureiskoe Reservoir Caused by a Large Landslide

Water Resources - The study considers the factors that had an effect on water quality in the Bureiskoe Reservoir (Far East) after a large landslide event in December 2018 (with a volume of 24.5...     

Microseismic Sounding and Active Faults of the Kerch-Taman Region

Izvestiya, Physics of the Solid Earth - Abstract—The results of integrated geological and geophysical studies of active faults and deep structure of the Kerch-Taman region are presented. Data...     

Deep Structure and Folded-Block Structure of the Garhwal Himalayas (India): Results of Integrated Geological and Geophysical Study

Geotectonics - The geological and geophysical study of the representative segment of the Alpine-Himalayan mobile belt—the Central zone of the Garhwal Himalaya—was conducted. The results...     

Valunistoe Epithermal Au–Ag Deposit (East Chukotka,Russia): Geological Structure,Mineralogical–Geochemical Peculiarities and Mineralization Conditions

Geology of Ore Deposits - The Valunistoe Au–Ag deposit is the third largest among epithermal deposits in Chukotka after the Kupol and Dvoinoe. It is located at the western closing of the East...