The Final Stage of Silicic Island Arc Magmatism in the Northern Urals

Doklady Earth Sciences - The date of cessation of calc-alkaline volcanic complex accumulation within the Devonian (Frasnian) island arc in the Northern Urals was determined for the first time. It...     

Specifics of the Deepwater Reception of Pseudo-Random Pulse Signals Propagating from the Shelf towards the Deep Ocean

Doklady Earth Sciences - The results of an experiment conducted in September 2017 are considered with regard to the applicability of the acoustic “mudslide” effect for positioning...     

Sedimentary Basins of the East Siberian Sea and the Chukchi Sea and the Adjacent Area of the Amerasia Basin: Seismic Stratigraphy and Stages of Geological History

Geotectonics - The seismic stratigraphy scheme for the shelf basins of the East Siberian Sea and the Chukchi Sea region and the adjacent deepwater area of the Amerasia basin has been developed, and...     

Natural and technogenic changes in the mode of rock deformation in the uranium deposit in granites

The Antey deposit in the southeastern Transbaikal region is one of the main objects of uranium ore mining. It is localized in the Late Paleozoic granite basement of the Strel’tsovo Caldera formed during the Late Mesozoic tectono-magmatic activation of geological structures in the region. Vein ore bodies of the deposit are controlled by steep near-meridional faults being developed in zones of intense hydrothermal-metasomatic alterations, cataclasis, brecciation, and elevated rock fracturing. The upper parts of the ore bodies are located at a depth of 400 m and their lower parts are traceable up to depths of 1300 m below the surface. The mining activity involves progressively deeper levels of the section, which determines the necessity for the complex assessment of the deposit potential. The mode of rock deformation at the four lower horizons of mines occurring at depths of 500 to 700 m is discussed. It is shown that variations in the mode of deformation are determined by a combination of natural and technogenic factors, which should be taken into consideration in predicting the geomechanic behavior of the rocks for safe mining works.     

Rescaling of fluid-conducting fault structures

The interrelation between geometric parameters (density and length) of the fault systems of four scale levels (kilometers, meters, centimeters, and millimeters) was established for the first time by detailed structural study of the rocks of the Urtui granite massif located in the western framework of the Strel’tsovskii uranium caldera in the Southeastern Transbaikalia. The further use of these geostructural data for conceptual and numerical modeling of the fluid filtration processes and transport of radionuclides in a three-dimensional crack and pore space in the variably deformed and metasomatically altered crystalline rocks was substantiated.     

Tectonomagmatic cycles and geodynamic conditions of formation of the ore-bearing systems in the Southern Argun’ Region

The evolution of the geological structure in the Southern Argun’ Region is studied in terms of changing geodynamic conditions of the Proterozoic, Caledonian, and Variscan Tectonomagmatic Cycles, which also under Mesozoic tectonomagmatic activation led to the formation of latite igneous rocks enriched in Au, Cu–Mo, Pb–Zn–Ag, volcanic and plutonic complexes of the caldera structures with Mo–U, Pb–Zn, and fluorite ores, and rare-metal granites with a Sn–W–Li–Ta spectrum.     

Geodynamic simulation of ore-bearing geological structural units by the example of the Strel’tsovka uranium ore field

Information on designing a 3D integrated model of the deflected mode (DM) of rock massif near the Strel’tsovka uranium ore field (SUOF) in the southeastern Transbaikal region is presented in the paper. This information is based on the contemporary stresses estimated by geostructural and tectonophysical techniques and by studying the seismotectonic deformation of the Earth’s surface using the data on earthquake source mechanisms and GPS geodesy focused on the recognition of active faults. A combination of the results of geostructural, geophysical, geotectonic, and petrophysical research, as well as original maps of faulting and the arrangement of seismic dislocations and seismotectonic regimes (stress tensors), allowed us to design models of the structure, properties, and rheological links of the medium and to determine the boundary conditions for numerical tectonophysical simulation using the method of terminal elements. The computed 2D and 3D models of the state of the rock massif have been integrated into 3D GIS created on the basis of the ArcGIS 10 platform with an ArcGIS 3D-Analyst module. The simulation results have been corroborated by in situ observations on a regional scale (the Klichka seismodislocation, active from the middle Pliocene to date) and on a local scale (heterogeneously strained rock massif at the Antei uranium deposit). The development of a regional geodynamic model of geological structural units makes it possible to carry out procedures to ensure the safety of mining operations under complex geomechanical conditions that can expose the operating mines and mines under construction, by the Argun Mining and Chemical Production Association (PAO PPGKhO) on a common methodical and geoinformational platform, to the hazards of explosions, as well as to use the simulation results aimed at finding new orebodies to assess the flanks and deep levels of the ore field.     

Estimation of the accuracy of methods for determining component masses for low-mass X-ray binary systems

Modern modeling of the population of low-mass X-ray binary systems containing black holes applying standard assumptions leads to a lack of agreement between the modeled and observed mass distributions for the optical components, with the observed masses being lower. This makes the task of estimating the systematic errors in the derived component masses due to imperfect models relevant. To estimate the influence of systematic errors in the derived masses of stars in X-ray binary systems, we considered two approximations for the tidally deformed star in a Roche model. Approximating the star as a sphere with a volume equal to that of the Roche lobe leads to slight overestimation of the equatorial rotational velocity V _rot sin i, and hence to slight underestimation of the mass ratio q = M _x /M _v . Approximating the star as a flat, circular disk with constant local line profiles and a linear limb-darkening law (a classical rotational broadeningmodel) is an appreciably cruder approach, and leads to overestimation of V _rot sin i by about 20%. In the case of high values of q = M _x /M _v , this approximation leads to substantial underestimation of the mass ratio q, which can reach several tens of percent. The mass of the optical star is overestimated by a factor of 1.5 in this case, while the mass of the black hole is changed only slightly. Since most estimates of component mass ratios for X-ray binary systems are carried out using a classical rotational broadening model for the lines, this leads to the need for appreciable corrections to (reductions of) previously published masses for the optical stars, which enhances the contradiction with the standard evolutionary scenario for low-mass X-ray binaries containing black holes.     

Simulation of turbulent flow over periodic bottom surface

A mathematical model is developed for the simulation of 2D turbulent flow over a periodic surface. An asymptotic solution is found which allows the estimation of the velocity field and tangential stress at a preset periodic form of a surface and rough peak heights. The solution allows the detection of the flow separation points and maximal tangential stress on the surface. The solution found for the near-bottom tangential stress is compared with experimental data on pressure regions of bottom waves and shows their good agreement.     

Tree wave migration across an elevation gradient in the Altai Mountains,Siberia

The phenomenon of tree waves(hedges and ribbons) formation within the alpine ecotone in Altai Mountains and its response to observed air temperature increase was considered. At the upper limit of tree growth Siberian pine(Pinus sibirica) forms hedges on windward slopes and ribbons on the leeward ones. Hedges were formed by prevailing winds and oriented along winds direction. Ribbons were formed by snow blowing and accumulating on the leeward slope and perpendicular to the prevailing winds, as well as to the elevation gradient. Hedges were always linked with microtopography features, whereas ribbons were not. Trees are migrating upward by waves and new ribbons and hedges are forming at or near tree line, whereas at lower elevations ribbons and hedges are being transformed into closed forests. Time series of high-resolution satellite scenes(from 1968 to 2010) indicated an upslope shift in the position ribbons averaged 155±26 m(or 3.7 m yr~(-1)) and crown closure increased(about 35%–90%). The hedges advance was limited by poor regeneration establishment and was negligible. Regeneration within the ribbon zone was approximately 2.5 times(5060 vs 2120 ha~(-1)) higherthen within the hedges zone. During the last four decades, Siberian pine in both hedges and ribbons strongly increased its growth increment, and recent tree growth rate for 50 year-old trees was about twice higher than those recorded for similarly-aged trees at the beginning of the 20~(th) century. Hedges and ribbons are phenomena that are widespread within the southern and northern Siberian Mountains.