Vol 473, No 2 (2017)

The first LA–ICP–MS U–Pb isotopic ages of detrital zircons from the Ordovician sandstones of the Sol–Iletsk Block (well 2–Ordovician), located at junction of the East European Platform with the Pre-Caspian Basin and the Pre-Uralian foredeep, are presented. Two detrital zircons with well-defined ages of 561 ± 4 and 570 ± 5 Ma were found in sample K15–501. They confirm the Ordovician age of the sandstones, which earlier had been defined on the basis of seismic–stratigraphic and lithological correlations. The age distribution of the detrital zircons indicates the significant role of Late Precambrian rocks as provenance sources. However, those rocks still remain unknown in the Early Precambrian basement of the Volga–Ural part of the EEP.

Based on mining works near water objects, a model of water permeability in an underworked site of a coalfield under the conditions of failure roof control is given. The secondary water permeability index varies in the section as a sawtooth function and depends on the strain intensity and lithology of rock beds. The coefficient of permeability reaches maximum values in intervals of split crack propagation, sandstones, limestones increasing towards the subfaces of beds, as well as towards the mined-out area in the lower part of the zone of water-conducting subsidence cracks. The coefficient of permeability in siltstone and mudstone beds normal to beds inside the upper and central parts of zones of water-conducting subsidence cracks is at a level of 0.003 m/day.

The relationship of events of igneous plume activity to the periods of low-carbonaceous clay shale deposition has been considered in the Riphean stratotype (western slope of the Southern Urals). The relation between plume events, warm climate periods, and active black shale deposition assumed in the Early Precambrian is poorly defined in the Late Precambrian.

In the framework of plane elastic problem we use a numerical approach to study the forms of opening and paths of growth of three parallel magma fractures as a model of dyke swarm formation and development. As expected, the internal dynamic mechanism of dyke interaction distorts their shapes in comparison with a single dyke shape, and curves their paths combining them into a divergent or a convergent system. The external dynamic mechanism of regional stress tends to align the growing dyke paths in parallel to the axis of the maximum compressive stress. The external and internal mechanisms compete with each other. The impact of the internal mechanism is stronger when the ratio of the distance between dykes to their length is less, the initial parallel dyke shift in relation to each other is larger, and the differential regional stress is less. Under the opposite conditions, the external mechanism prevails.

On the basis of quantum–chemical calculations of the linear to isomeric bent transition of the SiO₂ molecule, it is suggested that the bent to linear transition of SiO₂ forms can occur in melted mantle minerals of the lower mantle. This may be important for the formation of the peculiarities of mantle convection and origination of plumes.

Ga-bearing tourmaline was originally synthesized in boron, boron–alkaline, and boron–fluorine hydrothermal solutions at a temperature of 600–650°C and pressure of 100 MPa as crystals of spontaneous growth and on seeds. The maximal concentration of Ga₂O₃ in synthetic crystals reaches ~24.5 wt %. In addition to Ga-bearing tourmaline, Ga-bearing topaz crystallizes in boron–fluorine solution. Ga-bearing albite crystallizes in boron–alkaline solutions, whereas no additional phases are formed in pure boron solutions.

In Russia, highly radioactive liquid wastes from recycling of spent fuel of nuclear reactors are solidified into Na–Al–P glass for underground storage. The properties of the matrix including the radionuclide fixation will change with time due to crystallization. This is supported by the results of study of the interaction between glassy matrices, products of their crystallization, and water. The concentration of Cs in a solution at the contact of a recrystallized sample increased by three orders of magnitude in comparison with an experiment with glass. This difference is nearly one order of magnitude for Sr, Ce, and Nd (simulators of actinides) and U due to their incorporation into phases with low solubility in water. Based on data on the compositional change of solutions after passing through filters of various diameters, it is concluded that Cs occurs in the dissolved state in runs with a glass and recrystallized matrix. At the same time, Sr, lanthanides, and U occur in the dissolved state and in the composition of colloids in runs with glass, and mostly in colloid particles after contact with the recrystallized sample. These results should be regarded for substantiation of safety for geological waste storage.

New data are presented on the distribution of oxygen isotopes and conditions of the local isotope equilibrium in high-Al rocks rocks of Khitostrov Island showing abnormally low δ¹⁸O values (below–25‰). The temperatures of isotope equilibrium are within 400–475°C. The minimum δ¹⁸O values have been registered in the in plagioclase, whereas the same phases in kyanite-bearing rocks lacking corundum demonstrate δ¹⁸O values usually 3–5‰ higher. The fluid δ¹⁸O value varies from–22 to–16‰ at 475 ± 15°C, from–18 to–23‰ at 425 ± 25°C, and from–17 to–22‰ at 380 ± 15°C. The results obtained do not require abnormal depletion of δ¹⁸O values owing to the infiltration of an external fluid under the Svecofennian transformations. The association of corundum-bearing rocks with the basic intrusions, the presence of zircon cores of older ages compared to these rocks, and the peculiarities of rock chemistry may be ascribed to the fact that lower crustal layers of ancient rocks depleted in δ¹⁸O before metamorphism were captured by basite melts.

The molecular composition and distribution of the concentration of n-alkanes are considered for sediments of boreholes drilled in the shallow part of the Laptev Sea, in the area of Buor Khaya Gulf. The diverse molecular composition of n-alkanes is dominated by long-chain odd homologs, which indicate terrigenous organic matter (OM). Heterogeneous distribution and burial of OM are shown under conditions of pulsating contribution of river and thermoabrasive material and multiple changes in them up to hiatuses in sedimentation.

The mechanism of platinum biomineralization by microscopic fungi is displayed based on data of electron microscopy, infrared and X-ray photoelectronic spectroscopy. It was suggested the platinum sorption process by microscopic fungi has some stages. The initial interaction is carried out by the mechanisms of physical and chemical sorption. Hereafter the reduction process of adsorbed platinum ions up to zero state is performed, probably, for account of organic compounds, which are produced by fungi biomass as metabolism result, and the process terminates by nulvalent particles aggregating up to nanosize forms. Obtained data on the platinum biomineralization extends the concept concerning the character of forming platinum nanoparticles in carbonous paleobasin.

The distribution of organic and carbonate carbon in core samples from holes drilled in the shallow part of the Laptev Sea, in the region of Buor-Khaya Bay and Bykovskii Peninsula is considered. Significant heterogeneity in the distribution of carbon in the three columns studied is shown. Significant spatial heterogeneities in the distribution and burial of organic material (OM) under the conditions of a pulsing entrance of river and thermosabrasive material with repeated changes, as well as the mostly terrigenous origin of OM, are demonstrated.

The obtained results indicate that earthquakes of Mongolia form under the conditions of an alternating field of regional stresses, which is related to pulsed activations in the BRS and superimposed on the quasi-stationary field of global stresses of the Earth.

Sapropel from inland Russian water reservoirs is becoming a popular raw material for medicinal purposes, production of sorbents, organomineral fertilizers, and food supplements. A comparative study of the granulometric and biological properties of humic substances obtained from sapropel in a typical way and using ultrasonic treatment of the relevant reaction masses was performed at the Institute of Limnology of the Russian Academy of Sciences. It is shown that the humic substances of sapropel with an increased content of nanoparticles used as veterinary preparations lead to a significant economic effect without using imported preparations.