Shear Tectonic Fabric in the Atlantic Ocean and Its Relation to the Geodynamic Condition of the Upper Mantle and Intraplate Deformations

The tectogenesis of the Atlantic Ocean segments is complicated by the axial difference in spreading half-velocities, which causes additional shear displacements between the lithospheric blocks along the transform faults. The intensity of these processes and density of the fault zones iis related to the presence of “cold” sublithospheric lenses along the MAR at a depth of 500 km.     

Comparison of Supercontinent Cycles in the Metallogeny of Rare Earth Elements

The distribution of integrated resources of large and superlarge deposits (LSLDs) of rare earth elements (REEs) is compared to the current model of supercontinent cyclicity during Earth’s evolution. It is found that REE LSLDs are related predominantly to igneous complexes (carbonatite, nepheline syenites, syenite-alkaline granites, subalkaline granites), which are often additionally enriched in the hypergenic zone. A certain part of the resources is concentrated in independent hypergenic formations represented by placers and ion-adsorbed clays. Each supercontinent cycle—Kenoran, Columbian, Rodinian, Pangean, and Amasian—is expressed in the REE metallogeny in particular way: we revealed significant intercycle variations in the amount of REE LSLDs, the variety of their types, total accumulated resources, and some other characteristics.     

Estimating the Contributions of the Atlantic Multidecadal Oscillation and Variations in the Atmospheric Concentration of Greenhouse Gases to Surface Air Temperature Trends from Observations

We have quantitatively estimated the contributions of anthropogenic forcing characterized by variations in the atmospheric content of greenhouse gases and of natural variability characterized by the Atlantic Multidecadal Oscillation to the trends of global surface air temperature from observations since the middle of the nineteenth century on the basis of three-component autoregressive models.     

First Data about Mercury in Modern Hydrothermal Process in the Ocean,Juan de Fuca Ridge

The results of studying Hg in an underwater hydrothermal system in the ocean using the Middle Valley of the Juan de Fuca ridge as an example are presented. A significant part of Hg is accumulated in the basalt fundament (Holes 858F, G), forming anomalously high concentrations (up to 29.30 ppm) in certain parts. The high Hg contents were established in metalliferous sediments (323 ppm) of the sedimentary cover (Hole 858D) and in sulfide deposits (up to 10.30 ppm). In other parts of the section, Hg content is 0.02–0.76 ppm (Holes 858B, D, F), background Hg contents in sediments—0.08–0.28 ppm and in basalts—0.17–0.31 ppm (Holes 855A, C, D).     

Comparison of Organic Matter from Upper Jurassic Oil Shale of the East European Platform and the Bazhenov Formation by Molecular and Isotopic Data

The molecular and isotopic composition of an extract from the rocks of the Bazhenov Formation in the southeast part of Western Siberia, oils that are genetically related to this formation, and products of hydrous pyrolysis of the organic matter of oil shale (Middle Volgian) of the East European Platform were studied. Common features and differences in their molecular composition were shown. The carbon isotope composition for C₁₄–C₃₀n-alkanes was determined for the first time; a negative isotope anomaly was revealed for C₂₆n-alkane in all samples studied. It was concluded that in spite of the geographical distance, specific biota was revealed in the Volga Basin. This biota conditioned an isotopic indicator, which is genetically significant.     

The Nature and Age of Plagioclasites in the Ultrabasic Rai-Iz Massif (Polar Urals)

Corundum-containing and corundum-free plagioclasites localized in chromite-bearing ultramafites of the Rai-Iz Massif were explored for the composition and age. The composition of rock-forming minerals was studied, and the geochemical characteristics of the rocks were ascertained. The isotope age of plagioclasites determined by zircons using the U–Pb mode with a SHRIMP II device was equal to 398 ± 3 Ma. The age found conformed to the boundary on most of the Rai-Iz Massif took place against the background of a starting powerful collision, which caused the formation of the chromium mineralization of a high-chromic type, as well as the separation of a series of essentially plagioclase rocks of ruby mineralization at the discharge zones of the vein series.     

The 2006 (Мw 8.3) and 2007 (Мw 8.1) Simushir Earthquakes and the 2011 Tohoku Megaearthquake (Мw 9.0): Tectonic Stresses and Development of the Seismic Process

The peculiarities of catastrophic earthquakes that occurred in the Northwest Pacific region on January 13, 2007, and January 15, 2007, east of the Kuril Islands and the Tohoku megaearthquake of March 11, 2011, east of Japan are considered and analyzed. It is revealed that these earthquakes, apart from the fact that they occurred in the transition zone from the Pacific to island arcs and the Eurasian continent, have common features and similar characteristics. The seismotectonic slip in the source of the chronologically first event, the 2006 Kuril earthquake, was a gentle thrust, while that of the second event of January 13, 2007, was a downthrow beneath the Kuril deep trench.     

Dynamics of the Formation of Globular Silica Particles according to Dynamic Light Scattering

For the first time, the dynamics of the origination and growth of monodispersion spherical silica particles is studied by dynamic light scattering in the real-time mode. Experimental changes in the particle size and intensity of scattering during their formation and growth indicate the hierarchical formation of silica globules under various mechanisms of aggregation of particles.     

Neoproterozoic Rare-Metal Subalkali Leucogranite from the Northern Yenisei Ridge

Petrochemical study and U–Pb SIMS (SHRIMP–II) zircon analyses of subalkaline leucogranite of the Khariusikha Massif have been carried out. They have revealed for the first time a rare-metal mineralization. The elevated concentrations of rare elements (wt %) are Nb (0.5–0.7), Ta (0.12–0.16), REEs (0.08–0.24), Y (0.06–0, 1), Zr (2.3–2.6), Hf (0.1–0.12), U (0.05–0.1), and Th (0.08–0.1) and are confined to albitized granites. The main mineral phases concentrating the rare elements, U and Th, are tantalo–niobates: fergusonite, euxenite, U–pyrochlore, tantalite, as well as thorite, monazite, zircon, and sphene. These minerals associate with cassiterite, sulfides, and gold. The simultaneity of the intraplate granitoid magmatism (753 ± 4 Ma) and bimodal rhyolite–basalt volcanism (753 ± 6 Ma) in the neighboring rift structure has been demonstrated. Presumably, the Neoproterozoic rifting and intraplate magmatism relate to the plume activity that caused the supercontinent Rodinia to break up.     

Long-Term Geochemical Monitoring of the Source of the Angara River (Runoff from Lake Baikal)

The long-term data (1950–2017) on the chemical composition of the water from the source of the Angara River, which is the only run-off from Lake Baikal, a large and clean fresh water reservoir, are presented. The absence of water contamination despite the anthropogenic influence is shown. The similarity and constancy of the current composition of the waters in the lake and the Angara River are recorded. It is recommended to continue geochemical studies of this unique world heritage site.