Early Precambrian granite-gneiss complexes in the Central Aldan Shield     

S. D. Velikoslavinskii  A. B. Kotov  E. V. Tolmacheva  E. B. Sal’nikova  V. P. Kovach  A. M. Larin 《Petrology》2011,19(4):382-398

The central portion of the Aldan Shield hosts very widely spread Archean and Early Proterozoic granitoids, much of which are granite-gneisses. Geochemical lines of evidence, data on inclusions in minerals, and Sm-Nd isotopic geochemical data suggest that the protoliths of granite-gneisses in the central part of the Aldan Shield were granitoids that had various composition, age, and were derived from distinct sources and under different parameters and were then emplaced in different geodynamic environments. The granitoids belong to at least two types of different composition that occur within spatially separated areas. The protoliths of granite-gneisses in the western part of the Western Aldan Megablock and the junction zone of the Chara-Olekma and Aldan geoblocks (granite-gneisses of type I) had the same age and affiliated to the same associations as the within-plate granitoids of the Nelyukinskii Complex. Their parental melts were derived at 2.4–2.5 Ga by the melting of Archean tonalite-trondhjemite orthogneisses of the Olekma and Aldan complexes. The protolith of granite-gneisses in the eastern portion of the Western Aldan Megablock (granite-gneisses of type II) can be subdivided into two groups according to their composition: granitoids with geochemical characteristics of subduction- and collision-related rocks. The protoliths of the type-II granite-gneisses with geochemical characteristics of subduction granitoids were produced simultaneously with the development of the Fedorovskaya island arc (at 2003–2013 Ma), whereas the protoliths of the type-II granite-gneisses with geochemical characteristics of collision granitoids were formed in the course of accretion of the Fedorovskaya island arc and the Olekma-Aldan continental microplate at 1962–2003 Ma, via the melting of magmatic rocks of the Fedorovskaya unit and older continental crustal material.  相似文献   

An Integrated Study of the Dynamics of Electromagnetic and Acoustic Regimes During Failure of Complex Macrosystems Using Rock Blocks   总被引：1，自引：0，他引：1  

Kamel Baddari  Anatoly D. Frolov  Victor Tourtchine  Fayçal Rahmoune 《Rock Mechanics and Rock Engineering》2011,44(3):269-280

The development of the failure process in complex macrosystems using large rock samples subjected to biaxial compression has been studied by means of electromagnetic radiation (EMR) and acoustic emission (AE). In order to increase the stage of macrofailure development, a special procedure of rock loading was used to reveal regularities of nucleation and evolution of electromagnetic and acoustic structures. The synchronised measurements of EMR and AE allowed the control of the stress–strain state in the rocks and the structural developments of fracturing. Non-homogeneous distribution of the rock spatial crystalline structure subject to load leads to a mosaic distribution of EMR and AE characteristics. As a result, the crack scale effect may be observed in the EMR and AE structure behaviours. The EMR and AE following the failure at different levels behave differently according to the difference in the scale and type of cracks. Intense high-frequency EMR pulses were recorded during the initial stage of microcrack generation occurring prior to major failure of material. This was not the case for AE. The nucleation and development of the macroscopic progressive failure evolution caused an alternation in energetic and frequencial properties of electromagnetic and acoustic events. It has been detected that the tensile cracks were more efficient than shear cracks in capacity of EMR generation. The analysis of self potentials allowed reaching the maximum of registered anomalous variations in the stage of microcracking interaction. This stage showed an increase in the EMR activity, which implies the nucleation of microcracks in various regions of rock interfaces. The gradual accumulation of these defects led to weakening some parts of the rock along with a disintegration of electric anomalies, increase of AE and a significant fluctuation in the rate of EMR. When crack concentration attains its critical value, which results in the formation of dangerous macroscopic failure of higher level, AE shows an intense activity as well as an EMR lower frequency. The hierarchical development of rock failure using the ratio of the average crack size and the mean distance between cracks as a statistical concentration criterion is used to control the boundary of the transition from small dispersed cracks accumulation to gradual crack merger and the formation of the main macrofailure. These results could be transferred into larger scale levels to forecast dynamic events in the earth crust.  相似文献   

Stenian granitoids of the west Kyrgyz Ridge (North Tien Shan): Position, structure, and age determination     

K. E. Degtyarev  A. A. Tret’yakov  A. V. Ryazantsev  A. B. Kotov  E. B. Sal’nikova  P. A. Aleksandrov  I. V. Anisimova 《Doklady Earth Sciences》2011,441(1):1484-1488

In the structure of west Kyrgyz Ridge (North Tien Shan), a great role is played by complexly dislocated Upper Precambrian-Cambrian terrigenous-carbonate and shale strata, as well as by granitoids that comprise several coupled WNW-striking synforms and antiforms, the largest of which is the Makbal antiform. Southeast of the core of this antiform, granitoids comprise the large Kara Dzhilga massif and several massifs that are of lesser size and have tectonic correlations with the hosting terrigenous-carbonate strata. In the Kara Dzhilga massif, the rocks of three penetration phases are distinguished; contacts between rocks are often of tectonic character. The early phase is presented by monzonite and monzodiorite; the main one, by large-porphyric biotitic granites; and the additional one, by aplitic granites and pegmatites. By the chemical composition, granites of Kara Dzhilga massif of the main phase correspond to subalkaline granites of high-potassium calc-alkali series. The age of their crystallization (zircon-based U-Pb method) is 1131 ± 4 Ma (Stenian). The formation of Stenian granitoids in the North Tien Shan may be related to development of Grenville fold belts, whose fragments were identified in the units of the Central Asian Belt. Tectonic correlations between these granitoids and hosting terrigenous-carbonate strata appeared as a result of immersion to significant depths and subsequent exhumation into the upper crustal horizons in the Early Ordovician.  相似文献   

The Middle Riphean volcanogenic complex of Kokchetav massif (Northern Kazakhstan): Structural position and age substantiation     

A. A. Tretyakov  A. B. Kotov  K. E. Degtyarev  E. B. Sal’nikova  K. N. Shatagin  S. Z. Yakovleva  I. V. Anisimova 《Doklady Earth Sciences》2011,438(2):739-743

The volcanogenic Kuuspek Formation is a well-defined part of the succession of the Pre-Vendian complexes of the Kokchetav massif (Northern Kazakhstan). The formation is built up of mildly metamorphosed acid lavas, tuffs, and tuffaceous sandstones. At the reference site to the west of the Kokchetav Mountains, the rocks of the Kuuspek Formation compose hinges of small anticlinal folds with sericite-quartz schists of the Late Riphean Sharyk Formation forming the limbs. The Kuuspek Formation lavas are high-alumina rhyolites of high-potassium calc-alkaline series. The U-Pb zircon age of the rhyolites is 1136 ± 4 Ma, thus referring to the Middle Riphean. The Kuuspek rhyolites form the basal part of the Precambrian sedimentary cover of the Kokchetav massif. The cover also comprises schists, limestones, and dolomites of the Sharyk Formation, and quartzites and quartzitic schists of the Late Riphean Kokchetav Formation.  相似文献   

Manifestation of the 160-min solar oscillations in velocity and brightness (optical and radio observations)     

V. A. Kotov  A. B. Severny  T. T. Tsap  I. G. Moiseev  V. A. Efanov  N. S. Nesterov 《Solar physics》1983,82(1-2):9-19

All evidence of the solar origin of 160-min period oscillations is collected, and the present state of observations of this oscillation in optical and radio-ranges is considered. The main results are summarized: (a) the 160-min oscillation was observed in 1981 as well as before, (b) an attempt to find a nonradial component with l = 2 has failed, (c) the intensity and circular polarization of radioemission show with statistical significance the presence of this 160-min periodicity.Proceedings of the 66th IAU Colloquium: Problems in Solar and Stellar Oscillations, held at the Crimean Astrophysical Observatory, U.S.S.R., 1–5 September, 1981.  相似文献   

Statistics of voids in the two-degree Field Galaxy Redshift Survey     

Santiago G. Patiri  Juan E. Betancort-Rijo  Francisco Prada  Anatoly Klypin  Stefan Gottlöber 《Monthly notices of the Royal Astronomical Society》2006,369(1):335-348

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The Baikal Ice-Based Seismoacoustic Experiment     

Sobisevich  A. L.  Presnov  D. A.  Tubanov  Ts. A.  Cheremnykh  A. V.  Zagorskiy  D. L.  Kotov  A. N.  Numalov  A. S. 《Doklady Earth Sciences》2021,496(1):76-79

Doklady Earth Sciences - The results of a geophysical field experiment on the ice sheet of Lake Baikal are presented. The experiment was carried out in order to obtain a better understanding of...  相似文献   

Late Carboniferous Monzonite–Granosyenite Magmatism in the Northern Balkhash Region (Central Kazakhstan)     

P. V. Ermolov  K. E. Degtyarev  E. B. Salnikova  A. A. Tretyakov  A. B. Kotov  I. V. Anisimova  Yu. V. Plotkina 《Doklady Earth Sciences》2018,478(2):156-160

U–Pb dating of the Torangalyk Complex (Northern Balkhash) yielded a Late Carboniferous age of 305 ± 2 Ma. Taking into account the previous data, a new scheme for Late Paleozoic granitic magmatism in this region has been proposed. It includes the Early Carboniferous granite–granodiorite Balkhash Complex, Late Carboniferous monzonite–granosyenite Kokdombak and Torangalyk complexes, and the Late Carboniferous–Early Permian granite–leucogranite Akchatau Complex.  相似文献   

First Results of Study of Detrital Zircons from Late Precambrian Quartzite–Schist Sequences of the Aktau–Mointy Block,Central Kazakhstan     

N. A. Kanygina  A. A. Tretyakov  V. P. Kovach  K. E. Degtyarev  Kuo-Lun Wang  A. B. Kotov 《Doklady Earth Sciences》2018,479(1):320-323

For the first time, the U–Pb age is determined for detrital zircons of quartzite–schist sequences, which are part of the Precambrian basement of the Aktau–Mointy Block (Central Kazakhstan) along with Neoproterozoic felsic volcanic (925–920 Ma) and granitic (945–917 Ma) rocks [6]. We analyzed 219 zircon grains from small-grained quartzites of the northern part of the block (Mt. Bol’shoi Alabas) including 206 grains with concordant age (1149–1273, 1276–1975, 2354–2592 Ma). These ages indicate the Mesoproterozoic, Paleoproterozoic, and Neoarchean rocks as provenances. The youngest statistically significant age peak of 1209 Ma indicates that the quartzite–schist sequences accumulated 1200–900 Ma ago (at the end of the Mesoproterozoic and beginning of the Neoproterozoic) prior to the formation of the Early Neoproterozoic felsic rocks and granites.  相似文献   

Development of Oil and Gas Resources of Russia’s Arctic zone     

Oleg M. Barbakov  Marina L. Belonozhko  Anatoly N. Silin  Alexander S. Gyurdzhinyan 《Journal of the Geological Society of India》2018,92(6):764-766

The article dwells on the problems associated with the development of oil and gas Arctic region of Russia. It also suggests possibilities of their solution based on sociological studies conducted by the authors of representative samples in 2005, 2010 and 2015. Stressing the role and significance of sociological research in the general problem of the circumpolar regions by scientific study, the authors show the need for a sociological diagnosis in the context of different social groups. By doing so, characteristics of social problems inherent to the arctic region and requirements for scientific support of possible technologies is identified.  相似文献