Vol 475, No 1 (2017)

Detailed structural investigations were carried out in the Pevek area in order to verify the tectonic evolution of the Mesozoic thrust and fold belt in Chukotka. South-vergent F₁ folds in Triassic rocks were proved to be the earliest structures formed during the first deformation stage DI. These structures were deformed by north-vergent folds F₂ that were formed during the second deformation stage DII. North-vergent folds are the main structures of the Jurassic–Lower Cretaceous complex. The fold structures of the first two stages are deformed by shear folds F₃ finishing the stage DII. All these structures are deformed by submeridionally trending normal faults referred to the deformation stage DIII.

A new approach to the tectonic zoning of the consolidated crystalline basement and near-surface fold structures, taking into account the specific features of the structure of the Earth’s crust is suggested. As a result, a new regional tectonic map of these complexes of the Ural region was created.

The evolution of sedimentary rock formation of a highly organized level (paragenetic rock associations) is more complex than that of a poorly organized level (rocks). Subjacent rock associations are established for the entire geological evolution of the Earth: they varied in time and were obsolescent or, in contrast, nascent and momentary. A certain cyclicity of evolution is identified along with directed changes.

This work presents new data on the conditions of formation of igneous rocks on the western slope of the Southern Urals and the adjacent part of the East European Platform. Based on the calculated P–T melting parameters of the mantle substrate, it is shown that plume magmatism leads to the formation of similar rocks (picrites and picrite-dolerites), while the genesis of them is quite different. The first type of rocks is a product of crystallization of the undifferentiated mantle-derived melt in the upper horizons of the crust; the rocks of the second type are formed as a result of magma differentiation in large intracrustal magma chambers.

Geochronological studies of anorogenic magmatic complexes in the South Mongolian Hercinide have been carried out. Series of the massifs composed of alkaline and subalkaline granitoids with some monzonite formed during the interval of 318–316 Ma have been found. Taking into account previously obtained data, two groups of Late Paleozoic A-type granitoids different in age have been identified in the region: Late Carboniferous and Early Permian. These two occupy different structural positions. The location the early magmatic massifs is controlled by the extended Trans–Altai fault zone of northwest strike: the massifs cluster in areas of the fault intersection with boundaries of structural blocks formed by the pull-apart mechanism. The later Early Permian igneous complexes are associated with the Gobi–Tienshan rift zone of sublatitudinal strike.

The compositional and isotope–geochemical features of zircons from wehrlite of the Feklistov massif, which formed platinum coastal placers, are discussed in this paper for the first time. Zircons from wehrlite of the Feklistov massif, similarly to worldwide zoned clinopyroxenite–dunite massifs, are characterized by different morphology, composition and a wide spectrum of ages (from 2.717 to 0.373 Ga). The Late Devonian age (373.2 ± 7.5 Ma) of zircons allows us to characterize the timing of the formation of wehrlite from the Feklistov massif and to correlate its emplacement with a significant superplume event, which covered the Siberia and Laurussia continents. The geological meaning of this dating refers to limiting the lower age boundary for emplacement of the Feklistov clinopyroxenite–dunite massif into the Earth’s crust, which does not contradict geological observations.

Snow samples from the territory of the Setun River Valley Wildlife Sanctuary are analyzed for the content of rare-earth elements, heavy metals, and other hazardous elements by the inductively coupled plasma mass-spectrometry method. The changes in the concentrations of rare-earth elements, Pt, Pd, and indicator ratios of elements in the solid fractions of snow are revealed. A trend toward a decrease in the content of several elements northeastward of the Moscow Ring Road (MRR) is established. The level of seasonal atmospheric contamination of the area under study is assessed, and a possible source is identified.

Parts of the Fe–C–N system were studied in experiments at 7.8 GPa and 1350°C. It was shown that the admixture of nitrogen extends considerably the domain of melt stability in the system at temperatures close to the Fe–Fe₃C eutectic temperatures. Nitrogen solubility in cementite in equilibrium with the nitrogen- rich melt is below the detection limit of the EMPA technique applied. The metal melt is the only nitrogen concentrator (up to 4 wt % of N) in the range of compositions considered. The data obtained permit the conclusion that, in the case of complete dissolution of carbon and nitrogen, which might occur in the enriched mantle, native iron at ~250 km depth should either be completely molten or consist of a melt and carbide of iron.

The concentration and temperature dependences of pyrochlore and Nb oxide solubility in Na₂CO₃ and Na₂СO₃ + NaF aqueous solutions with concentrations from 0.01 to 2.0 m at 300–550°C and 50 and 100 MPa (the Co–CoO buffer) are studied. It is established that the Nb equilibrium content in the solution increases at 550°C and 100 MPa with an increase in mNa₂CO₃ and reaches the value of 10^–4m. The Nb₂O₅ solubility almost does not change as the concentration of Na₂CO₃ increases and is found within 10^–6 to 10^–5.5m.

A study of two classes of hydrocarbons (HCs)—aliphatic and polycyclic aromatic—in suspended matter of the surface waters and bottom sediments of the Northern and Middle Caspian Sea (R/V Nikifor Shurekov, October 2015) is described. It has been determined that oil pollution transported by river runoff and fluid streams flowing from sedimentary formations in the northeastern part are the main sources of hydrocarbons in the river–sea boundaries of the Volga, Terek, and Sulak rivers.

Mantle xenoliths containing phlogopite and phlogopite–amphibole mineralization from kimberlites of the Kuoika field have been studied. Such xenoliths were found in two series of rocks: magnesian (Mg) pyroxenite–peridotite and Fe-type phlogopite–ilmenite hyperbasite. The ⁴⁰Ar/³⁹Ar phlogopite age (1600–1800 Ma) and Re–Os and oxygen isotope data in rocks and minerals of the first series of rocks allow us to suggest that Phl–Amph metasomatism of the lithospheric mantle under the Birekte block and its accretion to the Siberian craton occurred in the subduction zone. The second series of rocks is comagmatic to potassium ultramafites and mafites, finding in the Siberian Platform. The phlogopite ages (870–850 Ma) from Phl–Ilm ultramafites corresponds to the beginning of the breakup of the supercontinent Rodinia and is close to ancient age datings of the alkaline ultramafic-carbonatite Tomtor massif. Phlogopite from xenoliths with garnet is much younger in age (500–600 Ma).

A new method of estimating the outgoing radiation spectra data obtained from the Hyperiоn EO-1 satellite is considered. In theoretical terms, this method is based on the nonequilibrium thermodynamics concept with corresponding estimates of the entropy and the Kullbak information. The obtained information estimates make it possible to assess the effective work of the landscape cover both in general and for its various types and to identify the spectrum ranges primarily responsible for the information increment and, accordingly, for the effective work. The information is measured in the frequency band intervals corresponding to the peaks of solar radiation absorption by different pigments, mesophyll, and water to evaluate the system operation by their synthesis and moisture accumulation. This method is assumed to be effective in investigation of ecosystem functioning by hyperspectral remote sensing.

Passive seismic observations were performed in the Vorotolovskaya deep well in Nizhny Novgorod oblast at a depth of 1400 m and in a well in the vicinity of Ufa at a depth of 500 m. Observations show significantly different acoustic impulse fluxes in these wells: hundreds per second in the Vorotilovskaya deep well and only few impulses per day in the Ufa well. It is supposed that it is the geological conditions that determine the character of seismoacoustic signals. A seismic observation technique is proposed for further studies of acoustic manifestations of radiation fields.

A general accurate solution to nonlinear shallow water equations is obtained in this paper. It describes the development of inertial oscillations on a rotating plane against a background sheared current of an arbitrary profile and explains the variety in the observed velocity hodographs of the inertial currents.

Statistical analysis of heat flow values measured in transform faults of the equatorial part of the Atlantic Ocean has been performed. Owing to the calculation using the Cramer–Welch criterion, it was established that not only is there an already known statistically significant difference between heat flow in active and passive zones of transform faults, but there is also an asymmetry in heat flow distribution between the western and eastern branches of passive zones of the fault zones. The western zones in all structures studied are characterized by higher average heat flow values. Two models are proposed to explain this phenomenon.