Vol 474, No 1 (2017)

The notions of deformations in the juncture area of the Eastern Arctic Shelf and Lomonosov Ridge are highly contradictory. It has been suggested that these geostructures were divided by a large right-lateral wrench fault of the transform type, which is known as the Khatanga–Lomonosov Fault. Data obtained by interpretation of the A7 profile have been compared with seismic sections crossing large-sized wrench faults in other sedimentary basins. The investigations have shown that on the A7 profile there are no structures typical of large-sized wrench faults. The Eastern Arctic Shelf and Lomonosov Ridge, which are located on the same lithospheric plate, form an integrated structure where the ridge is a natural continuation of the shelf.

The morphology of fossilized biogenic particles and the elemental composition of biogenic formations, discovered for the first time in Lower Silurian deposits within the Timan–Northern Urals region, are considered. The diversity of biogenic formations identified in stromatolites indicates a high level of activity of microorganisms forming the cyanobacterial mat and confirms the microbial origin of the Wenlockian stromatolite buildups.

The discovery of a layer of increased density in the liquid core at the boundary with the solid core gives grounds to suggest that solidification of the solid core occurs with an increase in total core volume and is accompanied by an increase in internal pressure in the core. This makes it possible to suggest a translational mechanism of energy transfer from the core to the Earth’s surface. It is suggested that the restoration of lithostatic equilibrium occurs via rising of a column of mantle material, uplift as result of elastic mantle deformation of the boundary of the transition layer at a depth of 420 km, and the formation of rising at the surface.

The seismic and emanation activity of fault zones at a geodynamic test site arranged in the vicinity of Ulaanbaatar to investigate dangerous geological processes in a heavily populated area of Mongolia is analyzed. It has been found that, at the modern stage of tectogenesis, destruction of the Earth’s crust occurs in the area of the strike-slip fault transformed from the Indo-Asian collision zone. Thus, a network of fault zones with seismic and emanation activity is developed in this area. In the vicinity of Ulaanbaatar, there are four systems of fault zones. The spatial pattern of the systems shows a nodal junction of comparatively large rightlateral and left-lateral strike-slip faults of submeridional and sublatitudinal orientation. These strike-slips are barely connected with a network of ancient faults. The northwestern and northeastern zones developed by compression and tension, on the contrary, inherit disjunctive structures of the most recent age located in a nodal junction at the tops of dihedral angles. Determination of the pattern of recent faulting is essential to estimate the seismic hazard for the capital of Mongolia, where more than one-third of the nation lives.

Granites, especially those that were decompressed as a result of processes of secondary transformations and tectonic movements, hold the greatest potential in the search for oil-bearing rocks in basements of sedimentary basins. Owing to the chemical dating of monazites from collision granites of the East Shebur area, the isochrone age of 274.5 ± 21 Ma was obtained. Zircons (SHRIMP-II) yield a concordant age of 277.5 ± 2 Ma (MSWD = 0.77). The Rb–Sr isochrone age of granites (247.4 ± 9.1 Ma) coincides with the emplacement time of the West Siberian rift system. This age records the process of intruding East Shebur granites into the upper crust level during riftogenesis and the extension of the study area. The younger age datings (231 Ma, 60 Ma (U–Pb); 220 Ma (K–Ar)) record the stages of tectonomagmatic activation, recorded in the basement of the Western Siberia oil-bearing areas.

U–Pb geochronological studies of igneous rocks of the Crimean Mountains were carried out for the first time. The ages of magma crystallization determined for gabbro–dolerites of the Dzhidair and Pervomaiskii intrusions point to the injection of these rocks during the Middle Jurassic Aalenian–Bajocian stage of magmatism. The Berriasian–Valanginian and Aptian age of sill-like bodies within the mass of volcanogenic–sedimentary rocks presumes the necessity to reconsider the common notion of an exclusively Albian magmatic event during the Cretaceous. High-precision U–Pb dating of magma intrusions allowed us to verify the age of Middle Jurassic magmatism and to distinguish the new Early Cretaceous Berriasian–Valanginian magmatism stage of basic composition.

This report presents the results of U–Pb geochronological LA–ICP–MS studies of detrital zircons from metasedimentary rocks of the western part of the Tukuringra terrane. The obtained data show that the Algainskaya, Garmakanskaya, and Teploklyuchevskaya series in the western part of the Tukuringra terrane are not of Middle Paleozoic but of Early Mesozoic age. It is shown that the main sources of clastic matter for these formations were Late Precambrian, Paleozoic, and Late Triassic–Early Jurassic complexes of continental massifs of the Amur superterrane.

Economic copper, nickel, and platinum-group element (PGE) deposits are associated with the Talnakh ultramafic–mafic intrusion of the Noril’sk Province in the northwestern part of the Siberian Platform. The results of the chemical Th–U–Pb dating of monazite from the ore-bearing melanotroctolites of the Talnakh intrusion are presented. The isotope-geochemical features of monazite are compared with zircon, sulfides, and baddeleyite.

The first results of geochemical and Sm–Nd isotope–geochemical studies of metavolcanic rocks, metagabbroids, and diabase of the Nora-Sukhotino terrane, the least studied part of the South Mongolian–Khingan orogenic belt in the system of the Central Asian orogenic belt are reported. It is established that the basic rocks composing this terrane include varieties comparable with E-MORB, tholeiitic, and calc-alkaline basalt of island arc, calc-alkaline gabbro-diabase, and gabbroids of island arcs. Most likely, these formations should be correlated with metabasalt and associated Late Ordovician gabbro-amphibolite of the Sukdulkin “block” of the South Mongolian–Khingan orogenic belt, which are similar to tholeiite of intraplate island arcs by their geochemical characteristics.

Ores of epithermal Au–Ag deposits of the Okhotsk–Chukotka volcanoplutonic belt are characterized by enrichment in a wide spectrum of elements in relation to the average upper crustal values. The data obtained show that the host volcanic rocks are the most likely sources of minor elements and REEs for the fluids that formed epithermal Au–Ag deposits of the Okhotsk–Chukotka volcanoplutonic belt.

For the first time based on determination of the geochemical occurrence forms of trace metals the main processes that control the accumulation of elements (Al, Mn, Fe, Mo, Cr, Ni, Co, Cu, Pb, Cd, and As) in the recent sediment cores from the White Sea and Barents Sea were quantified. A high-resolution study of the bottom sediment cores allowed us to estimate the short-term variations (periodicity of 10–15 years) in the accumulation of metals to reveal the periods of maximum Fe and Mn contents in the amorphous hydroxides fraction, which serve as effective adsorbents of the trace elements majority, including heavy metals. The Mn/Fe ratio in the amorphous hydroxides phase can be considered as geochemical indicators of early diagenesis.

We used a numerical model of the ocean circulation with a high spatial resolution to obtain estimates of the kinematic characteristics of Antarctic Bottom Water flow through the abyssal Vema Channel in the southwestern part of the Atlantic Ocean. The results of simulations correspond to the data of direct velocity measurements made at several locations in the channel. The high horizontal and vertical resolution of the model in the bottom layer allowed us to study in detail the hydrodynamics of this flow over its entire length.

This paper reports the results of processing and analysis of geomagnetic variations, estimates of their spectra, and the first identified waves of lunar–solar tides on the geomagnetic variation envelopes in the circadian range and in the periods of 13.66 and 27.55 days. The specific features of the geomagnetic variation spectrum open up new possibilities for evaluation of the viscosity of the Earth’s outer core, description of the geomagnetic dynamo, development of new models of movement of the Earth’s inner core and the current system dynamics in the outer (liquid) core, and establishment of the general regularities controlling the energy exchange conditions in the geosphere.

This paper reports proton mass spectrometry data on aromatic volatile organic compounds (VOCs) (benzene, toluene, phenol, styrene, xylene, and propylbenzene) obtained in different Russian regions along the Trans-Siberian Railway from Moscow to Vladivostok, based on expedition data retrieved using the TRO-ICA-12 mobile laboratory in the summer of 2008. The contribution of aromatic VOCs to ozone formation in the cities and regions along the measurement route has been estimated quantitatively. The greatest contribution of aromatic VOCs to ozone formation is characteristic of large cities along the Trans-Siberian Railway (up to 7.5 ppbv O₃) specified by the highest concentrations of aromatic VOCs (1–1.7 ppbv) and nitrogen oxides (>20 ppbv). The results obtained are indicative of a considerable contribution (30–50%) of anthropogenic emissions of VOCs to photochemical ozone generation in the large cities along the Trans-Siberian Railway in hot and dry weather against the background of a powerful natural factor such as isoprene emissions controlling the regional balance of ground-level ozone in warm seasons.

This paper presents the calculated heavy metal (Fe, Mn, Zn, Ni, Cu, Cr, Co, Cd, and Pb) flows in suspended and dissolved forms in the main navigable branches of the Don and Kuban river deltas during the low-water period of 2013–2014. This work is based on the data of field studies in which water and suspended matter samples were collected and the turbidity and water discharge in deltas were measured. A quantitative estimate of heavy metal inflows into the deltas of the Don and Kuban rivers is provided. Transformation of flows of suspended and dissolved metal forms from the delta top to the sea edge is discussed. The influence of localities (Rostov-on-Don, Temryuk) on the increase in heavy metal flows downstream is shown, and the heavy metal flows in the deltas of the Don and Kuban rivers are compared.