Home – Home – Jornals – Advanced Search

The onset of the modern tectonic style that combines plate-related and plume-related mechanisms has been discussed. Such a tectonic style could have started on the Earth when all layers of our planet had formed. Analysis of available geological data shows that the solid inner core crystallized by 2.7 Ga. Typical geologic complexes appeared on the continents as a result of plate tectonics processes at that time. The layer D ″ that accumulates lithospheric slabs, which do not remain at the upper-lower mantle interface but can go down to the core-mantle boundary, was finally produced by 2 Ga. At pressures and temperatures of the D ″ layer perovskite, a principal mineral of the lower mantle transforms into postperovskite phase. The isotope data suggest the existence of mantle (EM-I and EM-II) domains, being the sources for oceanic island basalts (OIB) and the depleted upper mantle (asthenosphere), the source for mid-ocean ridge basalts (MORB), from at least 2 Ga. It is accepted that the recent tectonic style started on the Earth at that period. Deep-seated processes suggest the involvement of all Earth’s layers. The asthenosphere-lithosphere interaction is responsible for different types of large surface structures that develop as fold mountains, oceanic spaces, and subduction zones. The descending lithospheric slabs (cold mantle material) and ascending mantle material in hot mantle provinces or the so-called low shear velocity provinces are responsible for the lower mantle convection. The plume is produced in the layer D ″, which accumulates the descending lithosphere slabs as well as light elements released from the outer liquid core, which are oxidized in this layer, thus resulting in thermochemical plume formation. At the same time the molten ferric iron penetrates the core. So, we see the interaction of all Earth’s layers. The article also considers the evolutionary history of the Siberian continent over 700 Myr as early as the breakdown of Rodinia and the formation of mountain folds and rifting structures and the associated metallogeny.

This paper provides the state-of-the-art discussion of major aspects of the composition and evolution of the Earth’s core. A comparison of experimentally derived density of Fe with seismological data shows that the outer liquid core has a homogeneous structure and a ~10% density deficit, whereas the solid inner core has a complex heterogeneous anisotropic structure and a ~5% density deficit. Recent estimates of the core-mantle boundary (CMB) and inner-core boundary temperatures are equal to 3800-4200 K and 5200-5700 K, respectively. Silicon and oxygen (up to 5-7 wt.%) are considered to be the most likely light element candidates in the liquid core. Cosmochemical estimates show that the core must contain about 2 wt.% S, and new experimental data indicate that the inner-core structure yields the best match to the properties of Fe carbides. Our best estimate of the Earth’s core calls for 5-6 wt.% Si, 0.5-1.0 wt.% O, 1.8-1.9 wt.% S, and 2.0 wt.% C, with the Fe ₇C ₃ carbide being the dominant phase in the inner core. The study of short-lived isotope systems shows that the core could have formed early in the Earth’s history within about 30-50 Myr after the formation of the Solar System, t ₀ = 4567.2 ± 0.5 Ma. Studies on the partitioning of siderophile elements between liquid iron and silicate melt suggest that the core material would form in a magma ocean at ~1000-1500 km depths and 3000-4000 K. The oxygen fugacity for the magma ocean is estimated to vary from 4-5 to 1-2 log units below the Iron-Wustite oxygen buffer. However, the data for Mo, W, and S suggest addition of a late veneer of 10-15% of oxidized chondritic material as a result of the Moon-forming giant impact. Thermal and energetics core models agree with the estimate of a mean CMB heat flow of 7-17 TW. The excess heat is transported out of the core via two large low shear velocity zones at the base of superplumes. These zones may not be stable in their positions over geologic time and could move according to cycles of mantle plume and plate tectonics. The CMB heat fluxes are controlled either by high heat production from the core or subduction of cold slabs but in both cases are closely linked with surface geodynamic processes and plate tectonic motions. Considerable amounts of exchange may have occurred between the core and mantle early in the Earth’s history even up to the formation of a basal magma ocean. However, the extent of material exchange across the CMB upon cooling of the mantle was no greater than 1-2% of the core mass, which, however, was sufficient to supply thermochemical plumes with volatiles H, C, and S.

There are continuing issues concerning the formation and reconstruction of the geographic position of the Neoproterozoic Yenisei Ridge-a key element of the western framing of the Siberian craton and the Central Asian orogenic belt. This study focuses on the inner structure, composition, and boundaries of the Central Angara terrane, which is the largest in the Transangarian segment of the Yenisei Ridge. We propose a scheme of fault deformation of the region and demonstrate that the fault tectonics of the Central Angara terrane is distinct from that of adjacent terranes. We study in detail the Yeruda pluton granitoids of the Teya complex, which indicate accretionary-collisional magmatic events in this terrane prior to its collision with Siberia. New geochemistry and SHRIMP U-Th-Pb zircon geochronology of the granites indicate that they formed in a collisional setting at 880-860 Ma. Integrated petromagnetic and paleomagnetic investigations yield a paleomagnetic pole significantly different from the corresponding Neoproterozoic interval of the apparent polar wander path (APWP) for Siberia. The difference in paleolatitudes between the Central Angara terrane and the Siberian craton at the time of the Teya granites formation was at least 8.6 degrees, which equals a latitudinal separation of at least 1000 km. We consider various possible positions for the terrane relative to the Siberian craton. These results demonstrate that the 880-860 Ma magmatic events in the Central Angara terrane are not related to events in the western margin of the Siberian craton. Therefore, they do not indicate the existence of a Grenville-age orogenic belt in this location, as proposed by some authors.

The geodynamic reconstruction using new data on the composition, age, and paleomagnetism of Neoproterozoic and Vendian-Early Paleozoic island-arc complexes has provided new insights into the evolution of the subduction zone magmatism over extensive areas of the Central Asian Orogenic Belt, including eastern Altai-Sayan, Transbaikalia, and Northern Mongolia. Comparison of the igneous complexes of modern and ancient ensimatic and ensialic island arcs in the subduction zone forms a basis for possible geodynamic scenarios of the subduction zone magmatism in Neoproterozoic and Vendian-Early Paleozoic island arcs in the zone of interaction between the Siberian paleocontinent and the Paleoasian Ocean, which take into account the composition of crustal and mantle (including mantle plume) components.

This study presents a 3D model of the P and S seismic velocities above the Kamchatkan slab obtained as a result of tomographic inversion of arrival times of body waves from deep seismicity in the subduction zone. Various tests performed have shown limitations of the spatial resolution of the model and provided arguments for the reliability of the major structures used in the interpretation. In the uppermost layer down to 20 km depth, the model reveals strong low-velocity anomalies coinciding with Holocene volcanoes of the Klyuchevskoy group and Kizimen. In the seismogenic zone at depths from 80 to 150 km, we observe a low-velocity anomaly, which probably reflects the presence of the relatively thick oceanic crust sinking together with the subducting slab. This anomaly may also represent a zone of phase transitions, melting, and release of fluids from the slab. In the cross sections, we observe vertical and inclined low-velocity anomalies connecting the slab with the volcanic groups that probably represent the paths of ascending fluids and melts, which feed the volcanoes. In the case of Kizimen, we observe a single conduit connecting the volcano with the slab transformation area at 100 km depth. Beneath the Klyuchevskoy group, we identify several linear inclined patterns having different dipping angles. This may show that the volcanoes of the group are fed from different segments of the slab and might be one of the reasons for the diversity of lava compositions in the volcanoes of the Klyuchevskoy group.

Results of apatite fission track dating have been summarized and correlated with stratigraphic, geoelectrical, tectonic, and geomorphological data. The average regional rate of rock denudation in southeastern Gorny Altai is reflected in three thermotectonic events: (1) Late Cretaceous-Early Paleogene tectonic activity with a denudation rate of ~200 m/Myr, related to the Mongol-Okhotsk orogeny; (2) Middle Paleogene-Early Neogene stabilization with peneplanation; and (3) Neogene-Quaternary «stepwise» tectonic activity with a denudation rate of ≤270 m/Myr, related to the distant impact of the Indo-Eurasian collision. We present results of study of the evolution of regional tectonic processes and topography over the last 100 Myr by analysis of digital and shaded elevation models and apatite fission track dating.

Evidence for the involvement of a subduction component in diamond generation is analyzed based on literature data and our studies. Examination of xenoliths of diamond iferous eclogites, including X-ray tomography analysis, testifies to the superposed character of most diamonds. Diamond generation is accompanied by the serious modification of eclogite substratum. Isotope-geochemical data show that the eclogites originated from oceanic-crust rocks. The oxygen isotope compositions of garnets and clinopyroxenes from websterite xenoliths are similar to the mantle average (5.3-5.6‰). The eclogite minerals vary considerably in oxygen isotope composition (δ ¹⁸O of 5.3 to 12.4‰). Diamonds of eclogitic paragenesis predominate dramatically in the placers of the northeastern Yakutsk diamond-bearing province. In placer eclogitic diamonds, δ ¹³C varies from -27.2 to -3‰ ( n = 28). In diamonds of ultrabasic paragenesis, the range of δ ¹³C values is much narrower (from -7.1 to -0.5‰). All diamonds of variety V have a lighter carbon isotope composition (from -24.1 to -17.4‰). In a wide range of crystals with a contrasting carbon isotope composition, the isotope composition of the rim tends toward the average mantle value. This suggests that the eclogitic diamonds grew first with the participation of carbon from subducted continental crust and finally with the involvement of mantle carbon.

Currently, thanks to works of the Nobel laureate O. Williamson, along with such forms of performance management as market and hierarchy (i.e. firm), there are also hybrids - a specific form of organization of transactions, constituting a compromise between market and hierarchy. However, despite an important role of hybrids in economic life, currently there are no practical techniques based on measurable characteristics, which would make it possible to assign economic structures to hybrids. The existing approaches to allocation of hybrids are either of theoretical nature, poorly suitable for use in practice, or based on subjective evaluations of external characteristics of economic entities. It is obvious that it is inconvenient nor methodologically, nor practically. The suggested paper attempts to offer a technique of a quantitative assessment of those substantial characteristics of hybrids, which are used by O. Williamson for their description, and to construct the algorithm of assignment of the economic structures to hybrids. The solution of the issue of extracting hybrids from the total number of economic entities will make it possible to set out informal structures in economy as well, along with the formal integrated structures, and to estimate the real extent of integration of the enterprises.

In dynamic development of market, there is a process of active integration of traditional methods of accounting, analysis, control and audit in a single analytical accounting system of data acquisition and processing. The aim of the research is to ground theoretical hypotheses and principles of accounting and analytical system of business organization management. The article presents the author’s concept of accounting and analytical system of business organization management in the context of accounting/reporting, analytical and control components, taking into account the principle of consistency and «synergistic effect». Such a system would make the accounting and analytical processes manageable, contribute to continuity of combining accounting and analytical operations into one process, help to conduct management analysis and audit, use the results in making management decisions as well as be able to influence positively the quality of the final accounting and analytical information and management decisions. The integrated accounting and analytical management system of financial and economic activities, which has a «synergistic effect», will make possible to manage business successfully on a full scale, form a general database, which facilitates a process of decision-making.