Arcanite from Fumarole Exhalations of the Tolbachik Volcano (Kamchatka,Russia) and Its Crystal Structure

The crystal structure (R = 0.0194) of arcanite β-K₂SO₄ was studied on a single crystal from exhalations of the Arsenatnaya fumarole, Tolbachik Volcano (Kamchatka, Russia). The mineral crystallizes at a temperature of ≥350–430°C and associates with langbeinite, aphthitalite, hematite, tenorite, johillerite, and others. Arcanite is orthorhombic, Pnma, a = 7.4763(2) Å, b = 5.77262(16) Å, c = 10.0630(3) Å, V = 434.30(2) ų, Z = 4. Its structure contains isolated SO₄ tetrahedra, whereas K cations center ten- and nine-fold polyhedra.     

Middle–Late Paleozoic Duplex Rifting of the Barents Continental Margin and the Role Played in Formation of the East Barents Megabasin

Based on analysis and interpretation of seismic and other geological-geophysical data, duplex rifting is identified in the Paleozoic evolution of the South Barents Basin. Its first, pre–Late Devonian, phase was manifested on the southeastern side zone that limited the Pechora Plate structures. After a certain pause, a second, pre–Late Carboniferous phase involved the western Barents Sea region, including the slope of the Central Barents Rise and the western South Barents Basin. Thus, Late Paleozoic riftogenic structures in the western and southeastern South Barents Basin formed at different times. All this caused an asymmetric structure profile and asynchronicity of evolution of the rift system sides. In the Mesozoic, under the effect of formation of the Novaya Zemlya fold-and-thrust structure, the asymmetry of the riftogenic trough became even more contrasting.     

Main Stages of Evolution of Pacific Ferromanganese Stromatolites and Oncolites

As exemplified by cobalt–bearing Fe–Mn crusts (ferromanganese stromatolite) of the Magellan Seamounts (Clarion–Clipperton Province), the main stages of the structural evolution of bacterial communities have been recognized. It has been demonstrated that the change of the stages is caused by the effect of major tectonic, volcanic, and other geological events.     

Formation Patterns of the Chemical Composition of Mine Waters in Eastern Donbas

This paper presents a summary of the quantitative substantiation for four main patterns relating to the changes in the chemical composition of mine waters in Eastern Donbas. The patterns and their origin and impact on the environment are characterized. This makes it possible to solve current practical and theoretical issues: to predict the main components of the environmental contamination, develop standards for treatment facilities, and forecast the transformation in the composition of surface waters, ground waters, and mine waters, and to solve successfully other ecological issues in Eastern Donbas.     

Low-Titanium Lamproites of the Ryabinoviy Massif (Aldan Shield): Crystallization Conditions and Lithospheric Source

Obtained data shows that high-potassic dyke rocks of the Ryabinoviy massif (Central Aldan) belong to low-titanium lamproite series (Mediterranean type) and are distinct with “classic” high-titanium lamproites. Based on Al-in-olivine thermometer, temperature of olivine–chrome-spinel pair crystallization varies in range between 1100 and 1250°C. This suggests lithospheric mantle source for the parental melt and makes role of mantle plume insignificant. High-precision data on olivine composition and bulk rock traceelement composition imply mixed source for the parental melt, consisted of depleted peridotite and enriched domains, originated during ancient subduction.     

Formation of Water-Bearing Defects in Olivine in the Presence of Water–Hydrocarbon Fluid at 6.3 GPa and 1200°C

The main trends of water dissolution in Fe-bearing olivine have been investigated in the olivine–H₂O–hydrocarbon fluid system in experiments at a pressure of 6.3 GPa, a temperature of 1200°C, and hydrogen fugacity ( fH₂) buffered by the Mo–MoO₂ equilibrium. The content and contribution of ОH defects of different types in Fe-bearing olivines depend on the composition of reduced fluids in the system. As the fraction of hydrocarbons in the fluid increases, the H₂O content in olivine crystals decreases from 900 to 160–180 ppm, while the ОН absorption peaks become lower at high frequencies and occupy a larger part of the infrared spectrum in the low-frequency region. According to the experimental results, even the deepest seated mantle olivines with OH defects were not equilibrated with a fluid rich in light alkanes or oxygenated hydrocarbons.     

Some Results of Oceanological Video Monitoring

The design features of an oceanological video-monitoring system created for operational research of coastal infrasonic wave processes are described. The results obtained confirm great opportunities for its use in fundamental and applied works in various seasons. The processing of the obtained experimental data has revealed the dynamics of the wave processes starting from wind waves to diurnal tides.

     

The Stress–Strain State of Recent Structures in the Northeastern Sector of the Russian Arctic Region

Doklady Earth Sciences - Complex research to determine the stress–strain state of the Earth’s crust and the types of seismotectonic destruction for the northeastern sector of the...