S.G. Arzhannikov, R. Braucher, M. Jolivet, A.V. Arzhannikova
Keywords: Late Pleistocene glaciation, glacial deposits, 10Be surface exposure dating, East Siberia
Analysis and summary of publications on southern East Sayan, eastern Tuva, and northern Mongolia have shown that the late Pleistocene glaciation covered a large area and had a complicated dynamics of glacier advance and retreat. Starting with MIS 5, the Todza Basin and, partly, the Oka Plateau, Azas Volcanic Plateau, Mondy Basin, and river valleys in southern East Sayan were periodically covered with ice. The thickness of ice in the eastern Todza basin was 700 m, on the Azas Volcanic Plateau it reached 300–600 m, and in the val-leys of southern East Sayan it is estimated as 700–800 m. The thickness of ice in the Mondy Basin was 300–350 m.
Geological and geomorphological studies and isotope surface exposure dating (10Be method) of boul-ders from terminal moraine complexes have provided evidence for extensive MIS 2 glacier advance in the Mondy Basin and in the Sentsa, Jombolok, and Sailag river valleys (southern East Sayan). The average age of exposure for three groups of samples is 14, 16, and 22 ka.
Isolated lenses of diamictites laying discordantly over the Late Riphean (Cryogenian) Kirgitei Forma-tion were found in the immediate vicinity of the Vendian Taseeva Group stratotype in the Taseeva River val-ley and assigned to the Shishina Member a few meters in visible thickness. The Shishina diamictites are, likely, of glacial origin as they (i) lie at the base of the Vendian section, (ii) consist of unsorted dolomitic clasts from fine gravel to more than 0.5 m boulders suspended in a mud matrix, and (iii) show glacial striation on clasts. The glacial origin is further supported by the morphology of stones, which resemble a smoothing iron or a bullet, with a swelly top, a flat bottom, and a steeply cut rear and form clusters produced by disinte-gration of larger boulders. The stones bear signatures of cleavage, cracks, grooves, and striation on the faces, while the matrix looks undeformed. The Shishina Member has no genetic relation with the underlying Kirgitei Formation but rather correlates sedimentologically with the Ulyakha Member tillites at the base of the Ven-dian Marnya Formation (Oselok Group) in the Sayan foothills. The Shishina Member stones may derive from the Late Riphean (Cryogenian) Dzhura Formation exposed 4 km downstream of the site along the Taseeva. They occur near the base of the Aleshinsky Formation (lowermost unit of the Taseeva Group) of cross-bedded glaciofluvial sandstone, gravelstone, conglomerate, and sandy gravel mixtite transported from east to west (from the Siberian Craton interior to its margins) and deposited in channel bars or as gravel lags. The lower member of the Aleshinsky Formation comprises two associations of clasts: (i) coarse quartzose sand and gravel and (ii) fine and medium quartz and lithoclastic sand. Rocks in the former are well rounded, with traces of wind erosion, while the latter association is composed of mechanically eroded angular material transported to short distances from a metamorphic and metasedimentary source on the Craton margin. The Aleshinsky clastics have their composition and grain size patterns similar to those of the glaciofluvial Plity, Nersya, and Kedrovy members of the Marnya Formation in the Sayan area. According to sedimentological evidence, the Shishina diamictites are tillites identical to the Ulyakha moraine at the base of the Sayan Oselok Group and may be a missing link in the Taseeva Group stratigraphy.
The composition of stable carbon and oxygen isotopes in the section of an isolated carbonate platform is analyzed. Traces of several global and subglobal transgressions and regressions have been found in the limestone strata. Some of these phenomena were associated with the Upper Kellwasser (at the Frasnian–Famennian boundary) and multiphase Hangenberg (at the Devonian–Carboniferous boundary) Events. Never-theless, there were no considerable sea level fluctuations in the platform water area. There is no evidence for subaerial erosion. The bottom water during sedimentation was mostly in oxic conditions.
We present results of study of mineral assemblages and PT-conditions of metamorphism of mafic gar-net–two-pyroxene and two-pyroxene granulites in the Early Precambrian metamorphic complex of the An-gara–Kan terrane as well as the U–Pb age and trace-element and Lu–Hf isotope compositions of zircon from these rocks and the zircon/garnet REE distribution coefficients. The temperatures of metamorphism of two-pyroxene granulites are estimated as 800–870 to ~900 ºC. Mafic garnet–two-pyroxene granulites contain gar-net coronas formed at 750–860 ºC and 8–9.5 kbar. The formation of the garnet coronas proceeded probably at the retrograde stage during cooling and was controlled by the rock composition. The age (1.92–1.94 Ga) of zircon cores, which retain the REE pattern typical of magmatic zircon, can be taken as the minimum age of protolith for the mafic granulites. The metamorphic zircon generation in the mafic granulites is represented by multifaceted or soccerball crystals and rims depleted in Y, MREE, and HREE compared to the cores. The age of metamorphic zircon in the garnet–two-pyroxene (~1.77 Ga) and two-pyroxene granulites (~1.85 and 1.78 Ga) indicates two episodes of high-temperature metamorphism. The presence of one generation (1.77 Ga) of metamorphic zircon in the garnet–two-pyroxene granulites and, on the contrary, the predominance of 1.85 Ga zircon in the two-pyroxene granulites with single garnet grains suggest that the formation of the garnet coro-nas proceeded at the second stage of metamorphism. The agreement between the zircon/garnet HREE distribu-tion coefficients and the experimentally determined values at 800 ºC suggests the simultaneous formation of ~1.77 Ga metamorphic zircon and garnet. Zircon formation by dissolution/reprecipitation or recrystallization in a closed system without exchange with the rock matrix is confirmed by the close ranges of 176Hf/177Hf val-ues for the core and rims. The positive εHf values (up to +6.2) for the zircon cores suggest that the protoliths of mafic granulites were derived from depleted-mantle source. The first stage of metamorphism of the mafic granulites and paragneisses of the Kan complex (1.85–1.89 Ga) ended with the formation of collisional grani-toids (1.84 Ga). The second stage (~1.77 Ga) corresponds to the intrusion of the second phase of subalkalic leucogranites of the Taraka pluton and charnockites (1.73–1.75 Ga).
Omphacite is a typomorphic mineral of eclogites, which is inappropriate to mineral assemblages of per-idotites. Nevertheless, findings of this mineral in inclusions in peridotitic diamonds can be considered as indi-rect evidence for the existence of this paradoxical mineral assemblage. In this paper we present experimental results on the interaction between carbonate-bearing amphibolite and olivine that model processes operated at the crust–mantle boundary in subduction zones. The experiments demonstrate growth of omphacite at the in-terface between acid melt and peridotite media at 2.9 GPa and 850–900 ºC; the omphacite coexists either with garnet and orthopyroxene or with phlogopite. The synthetic omphacite is exclusively of reactive-magmatic origin and does not form in metasomatic way. Findings of omphacite inclusions in peridotitic diamonds and in some pyroxenites from kimberlites are discussed in scope of the obtained experimental data.
Upper-mantle xenoliths in Cenozoic basalts of northwestern Spitsbergen are rocks of peridotite (spinel lherzolites) and pyroxenite (amphibole-containing garnet and garnet-free clinopyroxenites, garnet clinopyroxenites, and garnet and garnet-free websterites) series. The upper mantle section in the depth range 50-100 km is composed of spinel peridotites; at depths of 80-100 km pyroxenites (probably, dikes or sills) appear. The equilibrium conditions of parageneses are as follows: in the peridotites - 730-1180 ºC, 13-27 kbar, and oxygen fugacity of -1.5 to +0.3 log.un.; in the pyroxenites - 1100-1310 ºC, 22-33 kbar. The pyroxenite minerals have been found to contain exsolved structures, such as orthopyroxene lamellae in clinopyroxene and, vice versa, clinopyroxene lamella in orthopyroxene. The formation temperatures of unexsolved phases in orthopyroxene and clinopyroxene are nearly 100-150 ºC higher than the temperatures of the lamellae-matrix equilibrium and the parageneses in the rock. The normal distribution of cations in the spinel structure and the equilibrium distribution of Fe2+ among the M1 and M2 sublattices in the orthopyroxenes point to the high rate of xenolith ascent from the rock crystallization zone to the surface. All studied Spitsbergen rock-forming minerals from mantle xenoliths contain volatiles in their structure: OH-, crystal hydrate water H2Ocryst, and molecules with characteristic CH and CO groups. The first two components are predominant, and the total content of water (OH- + H2Ocryst) increases in the series olivine → garnet → orthopyroxene → clinopyroxene. The presence of these volatiles in the nominally anhydrous minerals (NAM) crystallized at high temperatures and pressures in the peridotites and pyroxenites testifies to the high strength of the volatile-mineral bond. The possibility of preservation of volatiles is confirmed by the results of comprehensive thermal and mass-spectral analyses of olivines and clinopyroxene, whose structures retain these components up to 1300 ºC. The composition of hypothetic C-O-H fluid in equilibrium (in the presence of free carbon) with the underlying mantle rocks varies from aqueous (>80 % H2O) to aqueous-carbonic (~60 % H2O). The fluid becomes essentially aqueous when the oxygen activity in the system decreases. However, there is no strict dependence of the redox conditions on the depth of formation of xenoliths.
Three minerals of the mayenite supergroup have been found in fluorellestadite-bearing metacarbonate rock (former fragment of petrified wood of ankerite composition) from the burned dump of the Baturinskaya-Vostochnaya-1-2 mine. These are eltyubyuite Ca
12Fe
3+10Si
4O
32Cl
6, its fluorine analog Ca
12Fe
3+10Si
4O
30F
10, and chlormayenite-wadalite Ca
12(Al,Fe)
14O
32Cl
2-Ca
12(Al,Fe)
10Si
4O
32Cl
6. The first two phases occur in the reaction mantle around hematite, magnesioferrite, and Ca-ferrite aggregates (“calciohexaferrite” CaFe
12O
19, “grandiferrite” CaFe
4O
7, and “dorrite phase” Ca
2(Fe
3+5Mn
3+0.5Mg
0.5)(Si
0.5Fe
3+5.5)O
20) and, rarely, as individuals in the fluorellestadite-cuspidine (± larnite ± rusinovite Ca
10(Si
2O
7)
3Cl
2) granular aggregate. Assemblages of zoned chlormayenite-wadalite crystals are found in the fluorellestadite-cuspidine granular aggregate, which lacks Ca-ferrite aggregates. Also, harmunite CaFe
2O
4, chlorellestadite, fluorapatite, anhydrite, rondorfite Ca
8Mg(SiO
4)
4Cl
2, fluorine analog of rondorfite Ca
8Mg(SiO
4)
4F
2, “Mg-cuspidine” Ca
3.5(Mg,Fe)
0.5(Si
2O
7)F
2, fluorite, barioferrite BaFe
12O
19, zhangpeishanite BaFCl, and other rare phases are identified in this rock. Data on the chemical composition and Raman spectroscopy of the mayenite supergroup minerals are given. The genesis of metacarbonate rock is considered in detail: “oxidizing calcination” of Ca-Fe-carbonates with the formation of hematite and lime; reaction between hematite and lime with the formation of different Ca-ferrites; formation of larnite as a result of reaction between SiO
2 and lime or CaCO
3; and reactionary impact of hot Cl-F-S-bearing gases on early assemblages. Eltyubyuite and its fluorine analog crystallized at the stages of gas impact. It is presumed that the maximum temperature during the formation of rock reached 1200-1230 ºC.
The 1370 km long 4-AR reference profile crosses the North Barents Basin, the northern end of the No-vaya Zemlya Rise, and the North Kara Basin. Integrated geophysical studies including common deep point (CDP) survey and deep seismic sounding (DSS) were carried out along the profiles. The DSS was performed using autonomous bottom seismic stations (ABSS) spaced 10–20 km apart and a powerful air gun producing seismic signals with a step size of 250 m. As a result, detailed P- and S-wave velocity structures of the crust and upper mantle were studied. The basic method was ray-tracing modeling. The Earth’s crust along the entire profile is typically continental with compressional wave velocities of 5.8–7.2 km/s in the consolidated part. Crustal thickness increases from 30 km near the islands of Franz Josef Land to 35 km beneath the North Barents Basin, 50 km beneath the Novaya Zemlya Rise, and 40 km beneath the North Kara Basin. The North Barents Basin 15 km deep is characterized by unusually low velocities in the consolidated crust: The upper crust layer with velocities of 5.8–6.4 km/s has a thickness of about 15 km beneath the basin (usually, this layer wedges beneath deep sedimentary basins). Another special property of the crust in the North Barents Basin is the destroyed structure of the Moho.
We studied changes in the properties of the geologic environment in the vicinity of the stationary 40-ton vibration source at time intervals between the vibration sessions. Experiments have shown that the quantity of the energy released in the environment with time depends on the frequency of an amplitude spectrum. We introduced parameter α characterizing this dependence and have established a linear regular increase in its module between the series of switch-on of the vibration source during the field observations. A hypothesis is put forward that there are zones that can rapidly change their stressed state, both accumulating and giving the accumulated energy. Comparative analysis of the stressed state of the experimental zone showed significant differences in the spatial distribution of the gradient of a new parameter (β) before and after active low-frequency impacts on the geologic environment.
The magnetic viscosity of geologic media exerts a significant, often high and sometimes predominant influence on the pulse induction characteristics measured in the laboratory and in the field. Compared with the frequency methods, measurement of pulse magnetization parameters has advantage, namely, magnetic viscosity is observed in the absence of the primary field, and the transitive pulse parameter is measured over a wide time range. This reduces the error of measurement of parameters characterizing magnetic viscosity. In contrast to the transitive parameter, its derivative, i.e., a pulse parameter, is not influenced by a constant (slowly decreasing) component of the total residual magnetization. This eliminates the problem of the uncertainty on the separation of low-viscosity component from the total magnetization. The temporal decrease in the pulse parameters of magnetization is described by the power function a · t-b , where a is the initial value (varies over a wide range) and b is the exponent close to unity. As shown by the measurements made with the use of induction coil systems, the parameter a shows a strong linear correlation with the frequency-dependent magnetic susceptibility Δ k , which is commonly used to evaluate the content of superparamagnetic particles. This suggests that the pulse induction systems can be used for an express study of a large number of samples in order to identify SP-particles and estimate their contents. Although the exponent b differs negligibly from unity, this difference is much higher than the error of determination of this parameter from the experimental data. Mathematical modeling of the pulse parameters of magnetization has shown that both are influenced by the distribution of the particle volume, which makes prerequisites for solving the inverse problem, i.e., finding the distribution that provides the best explanation of the experimental pulse parameters.
In this paper the results of magnetostratigraphic studies of the Upper Cretaceous penetrated by two wells (S-124 and S-114) drilled in the Tomsk structural-facies zone (Bakchar iron ore deposit) are presented. The obtained biostratigraphic data show that the sediments formed in the Campanian–Maastrichtian time in-terval. The high-temperature component of the remanent magnetization identified in the rocks allowed us to compile paleomagnetic columns for each well and correlate the columns, using paleontological data, with each other and with the general magnetostratigraphic and magnetochronological scales. In magnetostratigraphic sections of two wells, the Campanian reverse-polarity Slavgorod Formation (R(km)) with a normal-polarity horizon is correlated with Chron C33(r) (top) and C33(n) (bottom) of the Gradstein scale, and the Maas-trichtian normal-polarity Gan’kino Formation with a thin reverse-polarity horizon (N(mt)) is correlated with Chron C30 of this scale.
Three levels of the periodicity of volcanic eruptions with different causes and effects are recognized. The first, small-scale, level lasts tens to thousands of years and is due to the periodic accumulation of melt in the intermediate chambers and its periodical effusion both for internal reasons and under the trigger effect of external factors (solar activity, tidal changes in the Earth’s rotation rate). The second, medium-scale, level lasts hundreds of thousands to millions of years and is due to the periodicity of restructuring of spreading and subduction zones. The third, largest-scale and most prolonged, level of periodicity (30-120 Ma) is related to periodic accumulations of melt at the core-mantle boundary, ascent of mantle plumes, and subsequent acceleration of convection. These reasons are probably the major regulator of the average periodicity. Acceleration of convection in the asthenosphere, caused by periodic pulses of mantle jets, determines the changes in the group of moving plates through the changes of spreading zones. The intermediate periodicity level (hundreds of thousands of years to the first millions of years) is demonstrated by the example of Kamchatka and Japan, where the periodic changes in the intensity of subduction magmatism are due to the restructuring of back-arc basins (Shikoku, Sea of Japan, and South Kuril basin).
We present a comprehensive description of the blastomylonites of the Ikat thrust localized within the Ikat terrane in the East Transbaikalian branch of the Central Asian Fold Belt. The metamorphic rocks of the Garga block are thrust over the almost unmetamorphosed Cambrian deposits of the Ikat Formation. The geologic position of the thrust and the structure and mineral and petrochemical compositions of the blastomylonites in the suture zone are considered, and U-Pb dating of detrital zircon is carried out. The blastomylonites develop after the gneisses of the Garga block; the block protolith, admixed with felsic volcanic material, was no older than the Neoproterozoic (750-800 Ma). The
39Ar/
40Ar age of the thrust is estimated at 282 ± 0.4 Ma based on metamorphic biotite from the blastomylonites. The thrust marks the transpression period during the Late Paleozoic processes of tectonometamorphic activity related to the subsidence of the Mongol-Okhotsk oceanic crust beneath the Siberian continent.
We studied the geologic position, mineralogy, petrography, chemical composition, and age of granitoids of the Gamov batholith located in the Laoelin-Grodekovo terrane, southern Primorye (Russia). The studies have revealed four intrusive rock phases, from gabbro to leucogranites, in the massif. U-Pb zircon dating of tonalites of phase II and leucogranites of phase IV (254 ± 4 and 259 ± 2 Ma, respectively) shows that the intrusion of granitoids took place in the Late Permian without a significant gap in time. Structural investigations gave evidence for the intrusion in the sublatitudinal-compression setting. Geochemical studies have revealed granitoids of strongly different compositional types in the intrusive massif: gabbroids, quartz diorites and tonalites with characteristics of low-alumina TTG, calc-alkalic granodiorites and I-type granites, and medium-alkali leucogranites. The obtained data, together with the results of previous research into the Permo-Triassic granitoids of southern Primorye, reject the relationship of their formation with the evolution of the Solonker oceanic structures and suggest a more intricate tectonic scenario, which calls for additional study.
New data on metasomatic processes in the lithospheric mantle in the central part of the Arkhangelsk diamondiferous province (ADP) are presented. We studied the major and trace-element compositions of minerals of 26 garnet peridotite xenoliths from the V. Grib kimberlite pipe; 17 xenoliths contained phlogopite. Detailed mineralogical, petrographic, and geochemical studies of peridotite minerals (garnet, clinopyroxene, and phlogopite) have revealed two types of modal metasomatic enrichment of the lithospheric mantle rocks: high temperature (melt) and low-temperature (phlogopite). Both types of modal metasomatism significantly changed the chemical composition of the peridotites. Low-temperature modal metasomatism manifests itself as coarse tabular and shapeless phlogopite grains. Two textural varieties of phlogopite show significant differences in chemical composition, primarily in the contents of TiO2, Cr2O3, FeO, Ba, Rb, and Cs. The rock-forming minerals of phlogopite-bearing peridotites differ in chemical composition from phlogopite-free peridotites, mainly in higher FeO content. Most garnets and clinopyroxenes in peridotites are the products of high-temperature mantle metasomatism, as indicated by the high concentrations of REE and their pattern in these minerals. Fractional-crystallization modeling gives an insight into the nature of melts (metasomatic agents). They are close in composition to picrites of the Izhmozero field, basalts of the Tur’ino field, and carbonatites of the Mela field of the ADP. The REE patterns in the peridotite minerals make it possible to determine the sequence of metasomatic enrichment of the lithospheric mantle beneath the V. Grib kimberlite pipe.
The paper is concerned with study of melt inclusions in minerals of ijolite xenoliths at Oldoinyo Lengai Volcano. Melt inclusions with different phase compositions occur in forsterite macrocrysts and in diopside, nepheline, fluorapatite, Ti-andradite, and Ti-magnetite crystals. Nepheline contains primary melt inclusions (silicate glass + gas-carbonate globule ± submicron globules ± sulfide globule ± daughter/trapped phases, represented by diopside, fluorapatite, Ti-andradite, and alumoakermanite). The gas-carbonate globule consists of a gas bubble surrounded by a fine-grained aggregate of Na-Ca-carbonates (nyerereite and gregoryite). Fluorapatite contains primary carbonate-rich melt inclusions in the core, which consist of nyerereite, gregoryite, thenardite, witherite, fluorite, villiaumite, and other phases. In mineral composition they are similar to natrocarbonatite. Primary melt inclusions (glass + gas bubble ± daughter phases) are rare in diopside and Ti-andradite. Diopside and forsterite have trails of secondary carbonate-rich inclusions. Besides the above minerals, these inclusions contain halite, sylvite, neighborite, Na-Ca-phosphate, alkali sulfates, and other rare phases. In addition, diopside contains sulfide inclusions (pyrrhotite ± chalcopyrite ± djerfisherite ± galena ± pentlandite). The chemical compositions of silicate glasses in the melt inclusions vary widely. The glasses are characterized by high Na, K, and Fe contents and low Al contents. They have high total alkali contents (16-23 wt.% Na
2O + K
2O) and peralkalinity index [molar (Na + K)/Al] ranging from 1.1 to 7.6. The carbonate-rich inclusions in the ijolite minerals are enriched in Na, P, S, and Cl. The data obtained evidence that the parental melt in the intermediate chamber was heterogeneous and contained silicate, natrocarbonate, and sulfide during the ijolite crystallization. According to heating experiments with melt inclusions, silicate-carbonate liquid immiscibility occurred at >580 °C.
The relationships and chemical compositions of silver sulfoselenides in the ores of the Rogovik gold-silver deposit (northeastern Russia) were studied to refine the low-temperature field of the Ag
2S-Ag
2Se phase diagram and identify contradictions between natural and experimental data. Two types of relationships between the phases of the system Ag
2S-Ag
2Se have been recognized using optical and scanning electron microscopy: (1) Se-acanthite and S-naumannite occur as monomineral microinclusions or fill cracks in the grains or the interstices of other minerals, and acanthite (free of impurities) forms rims on Fe-sphalerite; (2) Se-acanthite forms rims on S-naumannite. Electron probe microanalysis of silver sulfoselenides from the Rogovik ores revealed 0-7.9 wt.% Se in acanthite and 0-3.2 wt.% S in naumannite, which corresponds to the acanthite series Ag
2S-Ag
2S
0.76Se
0.24 and naumannite series Ag
2S
0.28Se
0.72-Ag
2Se. The composition ranges of the studied acanthite and naumannite series are wider than those of natural silver sulfoselenides from the Guanajuato (Mexico), Silver City (USA), Salida (Indonesia), and other deposits (Ag
2S- Ag
2S
0.85Se
0.15 and Ag
2S
0.12Se
0.88-Ag
2Se, respectively) but are significantly narrower than the composition ranges of the synthetic samples: Ag
2S-Ag
2S
0.4Se
0.6 and Ag
2S
0.3Se
0.7-Ag
2Se. The presence of intergrowths of two phases of the Ag
2S-Ag
2Se series in the form of Se-acanthite rims on S-naumannite in the Rogovik ores and the absence of three-phase intergrowths of silver sulfoselenides Ag
2S
1-x Se
x from this and other deposits do not confirm the assumption on the existence of the third solid solution. The results of earlier studies of natural solid solutions Ag
2(S,Se) show the existence of two solid solutions (of the acanthite and naumannite series) in the system Ag
2S-Ag
2Se and confirm the experimental data. It is necessary to carry out a detailed examination of natural silver sulfoselenides falling in the interval from Ag
2S
0.4Se
0.6 to Ag
2S
0.3Se
0.7 in order to identify the limits of two-phase immiscibility.
The paper is concerned with geologic processes in river valleys, such as the movement of alluvial placers and mudflows, regarded as viscous fluids. The dynamics of distribution of the placer mineral and mud-and-gravel material in a river valley was studied by modeling. Moving material was examined as an independent flow of solid particles (solid flow), free of the enclosing rocks. The flow-environment interaction was specified by mass forces, friction forces, and substance sources (drains). For the mathematical description of a solid flow, a set of viscous-liquid equations was used. The placer and mudflow parameters obtained during the numerical experiments agree satisfactorily with the full-scale data for real objects.
We demonstrate application of the time-domain characteristics of induced polarization (IP) to the solution of prospecting problems on the flanks of the Julietta gold-silver deposit. The IP time-domain characteristics were analyzed by the Debye decomposition, which permits reconstruction of distribution of relaxation times. The experimentally determined dependences of the IP parameters on the main petrophysical properties of disseminated ores were used to interpret field data. Application of the Debye decomposition helped to distinguish zones with finely disseminated sulfide minerals in hydrothermally altered rocks, which were missed on the application of the standard technique for analysis of IP data. The estimated content of sulfide minerals in the altered rocks agrees with geological data.
Anisotropy of electrical conductivity in the lower mantle is regarded as a possible consequence of the phase transition of magnesiowϋstite from semiconductor into metallic state. We propose a method for obtaining information about the tensor of electrical conductivity of a deep anisotropic layer from geomagnetic data of the global network. It is possible to estimate the parameters of the electrical-conductivity tensor which are tangential components of the electromagnetic field by analysis of the characteristics of a magnetic mode. We present the results of processing of real data by the proposed method for the period from 1920 to 2009; the data were borrowed from the Net databank of the monthly values of components X, Y, and Z of the geomagnetic field.
O.P. Smekalin, A.V. Chipizubov, V.S. Imaev
Keywords: Paleoseismic surface ruptures, trenching, bracketing of the age of paleoearthquake
Subsection: GEOPHYSICS
In recent years, the Hustai, Gunji, and Kerulen paleoseismic structures have been discovered and examined within the Henteyn uplift. Their investigations revealed zones of probable earthquake foci, presenting a seismic hazard for Ulaanbaatar. We report the first data on the quantitative parameters of prehistoric earthquakes in the Meso - Cenozoic Upper Kerulen basin. The absolute age of two paleoevents determined by radiocarbon dating is within 1152 - 1702 BC and 5466 - 7201 BC. Seismogeological study of surface ruptures made it possible to estimate the type of tectonic stress during the formation of structures within the Henteyn uplift and to explain their nature. The horizontal-compression stress is mostly due to endogenous processes, which lead to the enlargement of the uplift area at the expense of the peripheral Mesozoic sedimentary basins.
In 2012, the renewable energy organization of Iran (SUNA) performed a gravity survey around hot springs of the Mahallat geothermal field in the Markazi Province of Central Iran, as part of the explorations and developments of geothermal energy investigation program in the region. The Mahallat region has the greatest geothermal field in Iran. This work presents interpretation results of various gravity maps and a calculated 3D inversion model. The residual gravity map shows three negative gravity anomaly zones (A1, A2, and A3) associated with the geothermal reservoirs in the region. The horizontal gradient maps reveal a complex fault system. In order to attain more information about the Khorhe geothermal reservoir, a 3D density contrast model was calculated using the Li–Oldenburg method. The attained 3D model provides an in-depth image of the evolution, showing the density contrast and the A1 zone having a high potential for the geothermal reservoir in the region. The results also show that the rocks which exist between 1000 and 3000 meters under the Earth’s surface in the Al zone are the most suitable aquifers for utilization of geothermal energy.
N. P. SAVINYKH1, V. A. CHERYOMUSHKINA2
a:2:{s:4:"TEXT";s:188:"1Vyatka State University of Humanities, 610007, Kirov, Leninа str., 198 2Central Siberian Botanical Garden, SB RAS, 630090, Novosibirsk, Zolotodolinskaya str., 101";s:4:"TYPE";s:4:"html";}
Keywords: biomorph, boimorphology, ontomorphogenesis, module, shoot formation model
On the basis of the concepts of I. G. Serebryakov (the founder of the science of plant life forms) and the analysis of current data the main directions of research and achievements of Russian botanists in the studying of life forms, as well as prospects for the development of biomorphology were shown. Plants were assessed as a distinctive group of living beings in the context of biological systems integrity. New approaches to habit characteristics, morphogenesis stages in relation to individual variations in ontogenesis, and classifications of plant life forms were considered. The role of systemic and dynamic approaches in description of plant life forms as modular organisms and the role of time as the forth dimension and fundamental category in plant habit formation were discussed. I. G. Serebryakov’s assumption of an evolutionary system of biomorphs as the system of parallel series of life forms similar to homologous series of hereditary variation was confirmed.
N. P. SAVINYKH, S. V. SHABALKINA, E. V. LELEKOVA
Vyatka State University of Humanities, 610007, Kirov, Lenin str., 198
Keywords: экологический тип, воздушно-водные растения, гелофиты, жизненная форма, побег, почка, адаптация, ecological type, air-water plants, helophyte, life form, shoot, bud, adaptation
Nine species of helophytes were described using the systematic approach: Alisma plantago-aquatica, Butomus umbellatus , Sagittaria sagittifolia, Sparganium emersum, Glyceria maxima, Phragmites australis, Scirpus lacustris, Typha latifolia, T. angustifolia. The species were divided into four groups according to their characteristics: monopodial rosette plants with a short rhizome, sympodial semirosette plants with a short rhizome, sympodial semirosette tuberous plants, sympodial plants with a long rhizhome. It was determined that maternal individuums and vegetative offsprings of polycarpic plants tended to become short-lived. This tendency was implemented in different ways.
N. M. DERZHAVINA
Orel State University, 302026, Orel, Komsomolskaya str., 95
Keywords: helophytes, hydrophytes, aerohydatophytes, acrophyllomic and laminаlic buds, hydropotes
On the basis of the study of helophytic and hydrophytic ferns, as well as literature data, adaptive strategies of their sporophytes were identified. A complex anаlysis of the photosynthetic apparatus of the plants was carried out at different levels of its organization : a) fronds, b) mesophyll cells, c) plastid apparatus. Among these species there had been a selection of the plants which were characterized by various biomorphs, active vegetative reproduction and accelerated passing of ontogenetic phases. As the result, the structures promoting aeration, maintenance of optimum water balance and effective photosynthesis had appeared.
The stages of ontomorphogenesis of willows and development of their life forms in different ecological environments were described. The willows belonged to different ecological groups, which structural features served as indicators of habitats. It was shown that the diversity of biomorphs was due to the morphogenesis process with species-specific morphobiological adaptations of shoot systems. At the same time the unique, genetically determined «architectural unit» of genus Salix L., — a triaxial biannual shoot complex, that formed willow’s crown, was retained.
M. V. Kostina, N. S. Barabanshchikova, G. V. Bityugova, O. L. Yasinskaya, A. M. Dubakh
Sholokhov Moscow State University for Humanities, 109240, Moscow, Tashkentskaya str., 18
Keywords: Betula pendula, annual shoot, architectural unit, reiterated complex, environmental conditions
The structure and formation of the crown of Betula pendula Roth. were studied from the perspective of the concept of architectural models and reiteration concept. Some peculiarities in formation and structure of an architectural unit and reiterated complexes due to total, partial, delayed, immediate, traumatic and automatic reiterations were detected. The specifics of these processes under different lighting conditions were identified. The trees crown structure in adverse environmental conditions in cities was studied. It was established that ecological plasticity and ontogenetic polyvariety of B. pendula were mostly determined by reiteration processes.
The shoot systems and ontomorphogenesis of Atragene sibirica L. were studied. Morphological and size polyvariety of all functional types of shoots were described. The high adaptive capacity of the shrub liana in terms of shoot formation in different environmental conditions was established.
Shoot formation and life forms of Thymus baicalensis were studied in different environmental conditions on the Olkhon island. Different life forms were typical for different habitats: in mountain steppes, on a hilltop — vegetatively-immobile aeroxylic dwarf shrubs, on a hillside — vegetatively-immobile prostrate dwarf shrubs, in sandy steppes — cushion-like life forms. The base part of the bush of adult individual forms was formed by the skeletal axis with monopodial and sympodial growth. Morphological adaptation mechanisms in different conditions is to change the structure of the axes, duration of the growth, the nature of rooting and position in space. The mechanism of morphological adaptation to different environmental conditions was expressed by changing the structure of the skeletal axes, duration of their growth, nature of rooting and position in space.
N. A. KARNAUKHOVA
Central Siberian Botanical Garden, SB RAS, 630090, Novosibirsk, Zolotodolinskaya str., 101
Keywords: Hedysarum L, ontomorphogenesis, life forms, adaptation, South Siberia
Sixteen species of
Hedysarum L. were studied in different eco-phytocenotic conditions in South Siberia. The peculiarities of vegetative reproduction, growth and dying of shoots, morphological structure, life span and modification of aboveground and underground shoots were described. The system of life forms of
Hedysarum L. was presented.
V. A. CHERYOMUSHKINA, A. A. GUSEVA
Central Siberian Botanical Garden, SB RAS, 630090, Novosibirsk, Zolotodolinskaya str., 101
Keywords: morphogenesis, life form, morphological adaptation, somatic evolution, Scutellaria supinа, Lamiaceae
The development of
Scutellaria supinа individuals was studied in the Asian part of the distribution range. Four life forms (subshrub, dwarf subshrub, taproot herbaceous polycarpic and long-rhizomatous-taproot herbaceous polycarpic) were described in different growing conditions. The mechanisms of structural transformations of individual plants and modes of morphological evolution of life forms of the species were detected.
The study concerned shoot formation and structural and morphological peculiarities of different life forms of
Nepeta pamirensis specimens, as well as their morphogenesis and its polyvariety in the conditions of the Pamir Mountains (Tajikistan). Depending on the habitat conditions,
Nepeta pamirensis specimens formed three life forms: herbaceous caudex taproot perennial plants, cushion semishrubs and aeroxylic semishrubs. For each life form the phases of morphogenesis were determined and the functional and zonal structure of shoot systems were described.
The mathematical model is developed and the swirling two-phase flow behind a sudden tube expansion is simulated numerically using the model of Reynolds stress transport. The gas phase is described by the three-dimensional RANS-equations taking into account the back effect of particles on transport processes in gas. To calculate the dispersed phase dynamics in a swirling confined flow, the Euler approach are used. It is found that with an increase in size, the particle are not involved into the separated flow and keep a positive value of the averaged axial velocity along the computational domain. Due to inertia of particle, the zone of reverse flows for the dispersed phase is noticeably smaller than the recirculation zone of gas phase. Performance of the developed mathematical model for description of the swirling two-phase flows in the presence of detachment areas is shown.
The model and the computer code FDS, albeit widely used in engineering practice to predict fire development, is not sufficiently validated for fire suppression by fine water sprays. In this work, the effect of numerical resolution of the large scale turbulent pulsations on the accuracy of predicted time-averaged spray parameters is evaluated. Comparison of the simulation results obtained with the two versions of the model and code, as well as that of the predicted and measured radial distributions of the liquid flow rate revealed the need to apply monotonic and yet sufficiently accurate discrete approximations of the convective terms. Failure to do so delays jet break-up, otherwise induced by large turbulent eddies, thereby excessively focuses the predicted flow around its axis. The effect of the pressure drop in the spray nozzle is also examined, and its increase has shown to cause only weak increase of the evaporated fraction and vapor concentration despite the significant increase of flow velocity.
The two-phase flow in the narrow short horizontal rectangular channels 1 millimeter in height was studied experimentally. The features of formation of the two-phase flow were studied in detail. It is shown that with an increase in the channel width, the region of the churn and bubble regimes increases, compressing the area of the jet flow. The areas of the annular and stratified flow patterns vary insignificantly.
Two-layer gas-liquid flows and evaporation intensity at the interface were studied. The influence of gas flow rate, longitudinal gradient of temperature, the Soret effect on the nature of flow and transfer processes was demonstrated. Experimental and theoretical results were compared; they show dependence of evaporation at the interface on gas flow rates.
The scheme of an integrated coal gasification combined-cycle power plant with small capacity is proposed. Using the built mathematical model a feasibility study of this unit was performed, taking into account the kinetics of physical and chemical transformations in the fuel bed. The estimates of technical and economic efficiency of the plant have been obtained and compared with the alternative options.
The phase-averaged velocity distributions were applied for calculation of parameters of a precessing vortex core; these were the input data for calculation of precession frequency by a formula derived from the helical vortex theory. It was demonstrated that the calculated frequency is within 10% error from the frequency measured in experiments. These results confirm the theory validity, and this opens opportunities for analysis of mechanisms controlling the precessing vortex core and external factors.
The constitutive effect of physical properties of liquid (pressure of saturated vapors and heat of vaporization) and the value of pressure in the vacuum chamber on the behavior of wall liquid film flowing into vacuum was determined experimentally. This behavior is characterized by liquid film rise, disintegration into droplets, and cooling down to freezing.
