The paper describes the problem of distortion of stacking velocities estimated from CDP gathers caused by statics applied for compensation of the effect of near-surface (NSS) velocity anomalies. An analytical solution of the problem of stacking velocities correction for statics applied for NSS and deep velocity anomalies is presented. The results of numerical modeling demonstrate the high performance of the proposed solution. A comparative assessment of the accuracy of structural imaging with the proposed methodology and the option without velocity correction and other algorithms for solving the problem is provided.
The morphology, chemical composition, ore and placer mineral associations of gold placers of the Ursky ore cluster and the less studied Kasminsko-Chesnokovsky prospective area of northeastern Salair indicate numerous and diverse primary sources, and the presence of gold in intermediate collectors. The fineness of 970-1000‰ is mainly due to hypergene-transformed gold. Placers were formed mainly due to quartz, quartz-carbonate, quartz-(carbonate)-sulfide veins and stockworks of the gold stage of mineralization, including superimposed on barite-polymetallic, with fine and finely dispersed gold, mineralization of the Ursky ore cluster and on dikes of the main composition. One of the sources of gold is also metasomatites (carbonate-micaceous, quartzites, quartz-albite-epidote, with rutile), accompanying gold ore bodies, or not associated with them. Differences in the typomorphic properties of placer gold are due to different contributions of primary sources. In the placers of the upper part of the Ur River, the Zvonchikha River, this is probably predominantly gold mineralization superimposed on dikes of the main composition. The gold has a high fineness (>910‰), it contains copper impurity (up to 1-6 wt.%) and, in one case, inclusion of Pd telluride. Quartzites are also a possible source of Au (as at the Kopna deposit). In the lower part of the Ur river placer, the Au fineness and the amount of copper-bearing gold decrease, and the frequency of occurrence of gold with mercury impurity increases. Gold mineralization is probably superimposed on polymetallic or localized in the rocks of the pechorkinsky complex. Polymetallic gold-bearing mineralization is indicated by the presence of gold with a fineness below 820‰ (as at the Iyunsky deposit). The sources of gold in the placers of the Chesnokovka and Kurnichikha rivers, in addition to mineralization associated with basic dikes, are mineralization characterized by gold with a fineness of 820-910‰ (including very small and fine), usually containing mercury impurity. These may be quartz veins and metasomatites on terrigenous rocks of the Suenginsky formation, known in the area. Inclusions in gold of placers of the Kasminsko-Ursky ore district are represented by minerals of sulfide ores, metasomatites, weathering crusts. In the gold of the Kasminsko-Chesnokovsky area, in contrast to the gold of the Ursky ore cluster, no inclusions of copper minerals (chalcopyrite, bornite, covellite, tennantite), common in pyrite-polymetallic ores, were found. The typomorphic properties of gold of the Aprelsky deposit reflect the multiplicity of sources, among them there are quartz veins, metasomatites on rocks of the Pecherkinsky formation, possibly mineralization superimposed on polymetallic. The sources of gold of the Khristinovsky Yama placer are probably diverse and similar to those of the placers of the Ur and Zvonchikha rivers. The isoferroplatinum grain from the Khristinovsky Yama placer can be attributed to the vilyuisky type.
The article presents new data on the formation conditions of basalts and basaltic andesites of the Kharchinsky volcano (the Central Kamchatka Depression, CKD). It is shown that the liquidus association is represented by olivine (Fo91) and Cr-spinel, which crystallized in oxidized conditions NNO+0.4 – NNO+1.5 at temperatures of 1110 – 1210°C. Melt inclusion in olivine phenocrysts study gives opportunity to reconstruct the parental melts for basalts and basaltic andesites. These melts have Mg-high (Mg# ≈ 76), Al-low and Ca-low mafic compositions enriched in volatiles. Water content in melts could reach up to 5.5 wt.%. These melts have a peridotite source; also, pyroxenite component admixture could take place. Crystallization of melts could occur in several intermediate chambers (up to 1.5, at 5-7 and 11-13 kbar).
V. A. Vernikovsky1,2, A. N. Semenov1,3, O. P. Polyansky1,3,A.E. Vernikovskaya1,2, N. Yu. Matushkin1,2,* 1Novosibirsk State University, Novosibirsk, Russia
2Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia
3V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia
Keywords: Arctic, Kara orogen, North Taimyr, Siberian craton, collision, granite, rheology, heat flow, 3D modeling
Using 3D numerical modeling, we consider the formation of the postcollisional granitoids of the Kara orogen in Northern Taimyr 280–250 Ma under the conditions of elevated heat flow due to the orogen’s breakup, prior to the magmatic activity of the Siberian mantle plume. The initial geometry of the model area, boundary conditions and physical properties of the crust and mantle were set to be close to the structure of the Earth crust in the junction zone of the Kara, Central Taimyr and Siberian blocks. The model shows that in the granite-gneiss – andesite-basalt layer of middle crust widespread melting takes place, and at the base of the crust – a 1–2 km thick zone of melting of the granulite layer is formed with the possible participation a mantle component. The magma ascent rate and the formation of groups of adjacent granitoid plutons depend on the value of the elevated mantle heat flow and the rheology of the melting protolith rocks. The model describes the conditions for intrusion of magma and formation of plutons 10–20 km in diameter at depths 5–8 km in unmetamorphosed rocks. 3D modeling shows the mechanism of periodic magma intrusion pulses at the postcollisional stage during 30–40 Myr. The proposed formation mechanism for the plutons allows to reproduce their shape and emplacement periodicity comparable to their actual geological position and age of the postcollisional granitoids of the Kara orogen. We compare the results of modeling in 2D and 3D configuration with identical model parameters and physical properties of the rocks. We conclude that 3D modeling is a more realistic and accurate means of description of the respective magmatic processes compared to the 2D one.
Small bodies of restitic ultramafic rocks composed of dunite and harzburgite and enclosed to gneisses of the Olkhon composite terrane (West Baikal Area) are described. P-T parameters of metamorphism of the ultramafic rocks correspond to metamorphic conditions of the embedding gneisses and amphibolite. Peculiar Al-rich ultramafic rocks, composed of forsterite, enstatite and Cr-free spinel are found in restite dunite and harzburgite. They contain high concentration of Al2O3 (up to 23 wt.%) and MgO (25-37 wt.%), low silica (30-42 wt.% SiO2) and very low CaO (less than 2 wt.%). We regard these rocks as products of syn-metamorphic high-temperature metasomatism (Max T=730-790°С) of the dunite and harzburgite. Comparison of the restitic and high-Al ultramafic rocks shows that in metasomatic process took part elements usually regarded low mobile - Al, Ti, V, Zr, REE, (input) и Mg, Si, Cr, Ni (output). There are no possible magmatic source of metasomatic fluids. We suppose that metamorphic felsic gneiss were the source of fluids in high-temperature metamorphic conditions. The impact of metasomatizing fluids on small fragments of aluminosilicate rocks in ultramafic rocks led to an even more significant enrichment of them with alumina (up to 50 wt.% Al2O3) and occurrence of specific mineral associations containing corundum and sapphirine.
YARMOLYUK V.V.1, KOZLOVSKY A.M.1, SAVATENKOV V.M.2 1Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian Academy of Sciences, Moscow, Russia
2Institute of Precambrian Geology and Geochronology RAS, St. Petersburg, Russia
Keywords: intraplate magmatism, basic rocks, Central Asia, rare elements, Sr–Nd–Pb isotopic composition, mantle plumes, plume-lithosphere interaction.
The Late Mesozoic – Cenozoic intraplate volcanic province of Central and Asia unites a number of spatially isolated volcanic regions. Three periods of activity are distinguished in the history of its development. The initial period (between ~145 and 100 million years ago) was characterized by a regional extension and riftogenic magmatism. The middle period (between 100 and 30 million years) was distinguished by a subplatform tectonic regime and an areal type of volcanism. The late period (the last 30 million years) is distinguished as a period of volcanic plateau.
The magmatism of the province is determined primarily by alkaline basic rocks.. During the rift period, trachybasalts and trachyandesites were formed, the geochemical feature of which was high REE contents with low Nb and Ta contents. During the period of areal volcanism, trachybasalts and alkaline basaltoids with OIB characteristics became predominant.
The trends in variations of trace elements and the isotopic composition of Sr, Nd, Pb in mafic rocks of different ages in the province were determined and the compositions of their magmatism sources were estimated. It was shown that at all stages of the province development, one of the components of the magma source remained constant and was close to the asthenospheric mantle of the EMORB type. During the rift period, subduction-metasomatized mantle also participated in magmatism. During the period of areal volcanism, the metasomatized mantle was gradually removed from the composition of melt sources. Since that time, the magmatism of the province has been determined by the interaction of asthenospheric, plume (OIB-type) and depleted lithospheric mantles.
The formation of the province is associated with the emergence of a hot mantle field at the base of the East Asian lithosphere. Its origin is consistent with the activation of deep geodynamic processes at the beginning of the Late Mesozoic, primarily with the activity of the Pacific superplume.
The article presents the results of an analysis of data obtained on the Yamm–Torzhok regional profile, which crosses the Ilmen anomaly of electrical conductivity along its main axis. These works continue the long-term study of the structure of the Precambrian basement complexes of the western part of the East European Platform by the staff of the Department of Geophysics of the Faculty of Geology of Moscow State University and GEMRC IPE RAS. Based on the obtained data, together with the analysis of potential fields, a deep geoelectric model was constructed, and a model of the sedimentary cover structure was presented separately.
A method for processing a set of hyperspectral data in order to form a representative system of features is proposed, and object classification is carried out using 7 different systems of features in narrow spectral intervals (30 nm) of the visible and near IR spectral regions based on measured spectral brightness coefficients (SBC). It is shown that it is advisable to use systems of three features for classification of 12 types of vegetation and camouflage coverings. At the same time, traditional vegetation indices often used for plant research provide insufficiently high accuracy of classification of objects of selected types. Simultaneous use of two difference indices is more effective in comparison with them. However, the best classification accuracy is provided by systems of three features, which are integrated values of the SBC in specially selected spectral ranges. Note that the classification accuracy is equal to or close to 100% in almost all cases when classifying objects into two classes.
B. P. ADUEV1, D. R. NURMUHAMETOV1, Y. V. KRAFT1, Z. R. ISMAGILOV1,2 1Federal Research Center of Coal and Coal Chemistry, Siberian Branch of the Russian Academy of Sciences, Kemerovo, Russia 2Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: coal, laser ignition, combustion, glow kinetics, ignition thresholds, ignition stages
Pages: 518-526
Laser ignition (1064 nm, 120 μs) of the dispersed particles of different coal marks was studied. For all coal marks, three consecutive ignition stages with characteristic threshold radiation energy densities ( H cr) for each stage were discovered. With an increase in the rank, the values of the first ignition limit H cr(1) remain almost constant, the second ignition limit H cr(2) decreases, while the third ignition limit H cr(3) increases. Results of the investigation of kinetic dependencies of flame glow at different ignition stages arising under the action of laser pulses on coal particles are presented. The glow duration at the first ignition stage slightly exceeds the duration of the laser pulse and reaches 150 μs for all marks of coal. The glow duration at the second ignition stage at H = H cr(2) is in the millisecond time interval. With an increase in the energy density of laser radiation, the glow duration at the second ignition stage decreases to the submillisecond range as a result of an increase in the rates of thermochemical reactions. At the third ignition stage at H = H cr(3), the glow duration is 10-100 ms for different marks of coal. It was established that for the studied coals, the glow intensity increases from the moment of exposure to laser pulse. In the submillisecond range, a decrease in glow intensity was observed. The glow amplitude of coals increases linearly with an increase in the energy density of laser radiation.
L. B. OKHLOPKOVA, O. S. EFIMOVA, L. M. KHITSOVA, Z. R. ISMAGILOV
Federal Research Center of Coal and Coal Chemistry, Siberian Branch of the Russian Academy of Sciences, Kemerovo, Russia
Keywords: carbon nanomaterial, bimetallic oxide nanoparticles, catalyst, thermal analysis, FTIR spectroscopy
Pages: 566-575
In order to develop new catalysts based on carbon nanotubes (Taunite) with deposited bimetallic oxide nanoparticles for oxidative desulphurization, a series of samples with the composition M1M2O x /Taunite (M1M2 = CeMo, CuMo, CeCu) was prepared by incipient wetness impregnation. The properties of the catalysts were studied by means of FTIR spectroscopy and thermal analysis combined with mass spectrometry. The effects of the nature of a metal precursor and the oxidative treatment of the support on the functionalization of the support surface and support thermal stability were studied. Decomposition of supports with deposited bimetals was determined to start at a temperature lower by 210-285 °C than in the case of non-modified support. The stability of Taunite support against thermal decomposition increases in the following series of metal cations: CuMo < CeMo < CeCu < support without M1M2. The optimal precursors of bimetals for the synthesis of a promising nanosized catalyst M1M2O x /Taunite were selected.
