Distribution and Sources of Methane in the Water Layers of the Antarctic Straits: Bransfield Strait and Antarctic Sound

Oceanology - Methane concentrations were measured in the water layers on two transects crossing the central part of Bransfield Strait and along the Antarctic Sound. In the abyssal sea of the...     

Currents in the Western Part of the Weddell Sea and Drift of Large Iceberg A68A

Oceanology - The drift of the large (length 160 km, area 5800 km2) A68A iceberg in the western part of the Weddell Sea is considered. Analysis was carried out on the basis of satellite images and...     

Study of nanocrystals in the dynamic slip zone

Mineral composition is studied and a search to detect nanocrystals is conducted in the surface layers of slickensides formed due to dynamic slip in arkose sandstone. The infrared and Raman spectroscopy show that the slickensided layer is composed of nanocrystals of montmorillonite and anatase measuring ??15 nm and 3 nm, respectively. The crystalline lattice of the nanocrystals of montmorillonite is stretched by ??2.5% while the lattice of the nanocrystals of anatase is compressed by ??0.12%. Deeper than 3 mm below the slickenside surface, the sandstone contains nanocrystals of montmorillonite, beidellite and nontronite, quartz, plagioclase, and anatase. The nanocrystals of anatase have a linear size of ??8 nm. Their crystalline lattice is compressed by ??0.03%. It is supposed that montmorillonite in the slickensides was formed due to hydrolytic decomposition of silicates under friction of the fault planes sliding past each other.     

A new spectrum analyzer for radio astronomical studies with the radio telescope RATAN-600

The spectral measuring facility with a new Fourier analyzer for use with the radio telescope RATAN-600 is described and its experimental data are reported.     

Crystal chemical and geochemical features of genetically different paleozoic dolomites in the Volga–Ural region

The comparative analysis of primary sedimentary and secondary catagenetic dolomites revealed that they differ in many typomorphic properties. Sedimentary dolomites are characterized by the pelitomorphic and fine-grained structure, high stoichiometry, and presence of the electron-hole (p-n) centers [SO₂]^– and [SO₃]^– in the structure. Secondary dolomites have a fine- to medium-grained structure and distinguished by a lower degree of stoichiometry. Their crystal lattice shows isomorphous replacements Mg ? Fe and Mg ? Ca. They can be divided into two (massive and porous) varieties. The massive varieties are characterized by the conformal structure and xenomorphic habitus of the closely packed idiomorphic and hypidiomorphic grains. The Ca–Mg and Fe–Mg isomorphism in the massive dolomites is less expressed than in the porous varieties. These specific features of dolomite varieties are related to their different formation settings. The porous dolomites were formed in a free environment that fostered slow growth of the relatively large equant crystals with a high degree of isomorphism, whereas the massive dolomites were formed under “stringent constraints” during a faster growth of crystals.     

On the priority of toxicological ‘hazard’ of nickel in the sea

Ranking of the major pollutants in the World Ocean according to their ecological hazard is of great importance for monitoring programmes. A critical analysis is given of Ketchum's conclusion that nickel pollution in the sea presents the greatest ecological danger of all the heavy metals. This conclusion seems to have been the result of using in calculation unwarrantably low values of nickel toxic concentrations, listed in the Water Quality Criteria proposed by the US National Academy of Sciences.