Home – Home – Jornals – Avtometriya 2007 number 1

We discuss problems of the origin, settings, and age of Neoproterozoic A -type leucogranites widespread in the Yenisei Ridge. Combined analysis of geological, petrological, and geochemical (including isotope) data shows that some granitoids (Glushikha complex) were formed at the postcollisional stage (750-720 Ma), and others (Tatarka complex), in an anorogenic environment (680-630 Ma). The anorogenic complex contains diverse igneous rocks, including alkaline varieties and carbonatites. Leucogranites form separate plutons within different igneous complexes. They have high contents of potassium (up to ultrapotassic composition in the Glushikha complex), iron, and fluorine and are depleted in europium. Postcollisional granitoids show the highest concentrations of Rb, Th, and U, extremely low concentrations of Ba and Sr, whereas anorogenic granitoids are rich in Ta, Nb, Y, Sm, and HREE. The obtained data point to the augmented mantle contribution to the formation of continental crust of the Yenisei Ridge between 750 and 630 Ma. We also report new results of U-Pb zircon dating, including SHRIMP and Ar-Ar data.

We investigate extension events in the southern Siberian craton between 1.8 and 0.7 Ga. Signature of Late Paleoproterozoic within-plate extension in the Northern Baikal region is found in 1674 ± 29 Ma dike swarms. A Mesoproterozoic extension event was associated with intrusion of the 1535 ± 14 Ma Chernaya Zima granitoids into the Urik-Iya graben deposits. Neoproterozoic extension recorded in the Sayan-Baikal dike belt (740-780 Ma dike complexes) was concurrent with the breakup of the Rodinia supercontinent and the initiation of the Paleoasian passive margin along the southern edge of the Siberian craton. The scale of rifting-related magmatism and the features of the coeval sedimentary complexes in the southern Siberian craton indicate that Late Paleoproterozoic and Early Mesoproterozoic extension did not cause ocean opening, and the Paleoasian Ocean opened as a result of Neoproterozoic rifting.

The paper summarizes paleomagnetic results obtained from the Neoproterozoic rocks of the western margin of the Siberian craton. On the basis of the obtained paleomagnetic poles and available paleomagnetic data for the Precambrian of Siberia, a new version of the Neoproterozoic segment of the apparent polar wandering path (APWP) is proposed for the craton and is compared with the Laurentian APWP. The superposition of these paths suggests that in the Neoproterozoic the southern margin of the Siberian craton (in modern coordinates) faced the Canadian margin of Laurentia. Most likely, in the end of the Mesoproterozoic and during the Neoproterozoic the Siberian craton and Laurentia were connected to form the supercontinent Rodinia. At 1 Ga the western margin of the Siberian craton was a northern (in modern coordinates) continuation of the western margin of Laurentia. The available paleomagnetic data on Laurentia and continental blocks of Eastern Gondwana (Australia, Antarctica, India, South China) and the proposed APWP trend allowed a new model for the breakup of this segment of Rodinia. Analysis of a total of the data available suggests that strike-slip movements on the background of the progressive opening of the oceanic basin between Siberia and Laurentia were predominant in the south of the Siberian craton during the Neoproterozoic. Similar kinematics is typical of the western margin of Laurentia, where strike-slip motions are probably associated with the progressive opening of the ocean basin between Laurentia and eastern Gondwana.

We suggest new age constraints for regional stratigraphic units and a model of the Neoproterozoic geodynamic evolution of the southern Siberian craton proceeding from our data on genesis and lithology of sedimentary and volcanosedimentary complexes and their correlation combined with published geochronological and chemostratigraphic evidence. Large-scale rifting events in the region may have occurred between 1000 and 850 Ma in the east and between 780 and 730 Ma in the west. The latter time span correlates with the breakup of the Rodinia supercontinent. The interval of 780-680 Ma corresponding to the deposition of the Dalnyaya Taiga regional stratigraphic unit was marked by the onset of collision and the development of an island arc and a back-arc basin in the eastern part of the territory. The basal strata of the Baikal and Oselok Groups and their equivalents presumably deposited at about 730 Ma, and their signature of glacial events correlates with the global Sturtian Glacial. The deposition of the Zhuya unit between 680 and 630 Ma was associated with development of a foreland basin which gave way to a system of orogenic foredeeps in the Early Vendian (since 630 Ma). Our studies furnish new data on the stratigraphy of the Baikal Group and shed more light on its complex structure and ambiguously interpreted deposition sequence.

We studied geology and main rock assemblages of the Precambrian Kan, Arzybei, and Derba terranes of the Central Asian Fold Belt which border the Siberian craton in the southwest. The Precambrian terranes include three isotopic provinces (Paleoproterozoic, Mesoproterozoic, and Neoproterozoic) distinguished from the Sm-Nd isotope compositions of granitoids, felsic metavolcanics, and metasediments. The terranes formed in three stages of crustal evolution: 2.3-2.5, 0.9-1.1, and 0.8-0.9 Ga. Proterozoic juvenile crust was produced by subduction-related magmatism; it was originally of transitional composition and transformed into continental crust by potassic plutonism as late as the Late Vendian-Cambrian. Terrigenous sediments in the Arzybei and Derba terranes vary in T (DM) Nd model ages from 1.0 to 2.0 Ga. The Nd ages of the underlying metavolcanics and lowest T (DM) of metasediments indicate that terrigenous sedimentation started in the Neoproterozoic. It was maintained by erosion of Mesoproterozoic-Neoproterozoic crust and, to a lesser extent, of Early Precambrian rocks on the craton margin or in Paleoproterozoic terranes. Ar-Ar dating of amphiboles and biotites from metamorphic rocks and U-Pb dating of zircons from granitoids yielded 600-555 and 500-440 Ma, respectively, corresponding to the Vendian and Early Paleozoic stages of nearly synchronous metamorphism and plutonism. Accretion and collision events caused amalgamation of the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic terranes in the Vendian and their collision with the Siberian craton. The lateral growth of the paleocontinent completed in the Late Ordovician.

In the Late Cambrian-Ordovician, Gondwana-derived microcontinents such as Kokchetav, Altai-Mongolian, Tuva-Mongolian, and Barguzin, as well as the Kazakhstan-Tuva-Mongolian island arc or a system of island arcs were involved in intense accretion-collision processes in similar geodynamic settings on a vast territory of Central Asia - from West Kazakhstan to Lake Baikal. The processes were likely to be the result of a large rebuilding of the Earth's crust possibly related to the increased mantle impact on the lithosphere as they were simultaneous to the opening of the Uralian and Mongolian-Okhotsk (Turkestan) Oceans. The 970-850 Ma breakup of Rodinia and the 760-700 Ma important tectonic events were followed by the Late Cambrian-Early Ordovician plume magmatism impulse at 500-480 Ma, which led to the opening of new oceans and accelerated the accretion of the Gondwana-derived blocks to the island arc and subsequent formation of an extended - more than 6000 km long - Kazakhstan-Baikal orogenic belt.

Blueschists are constituents of subduction-accretion complexes, where they occur either as separate tectonic slabs, slices, and lenses, or as exotic blocks in a melange. Often associated with ophiolites, blueschists are commonly metamorphosed members of ophiolite sections. Along with ophiolite, a typical component of high-pressure belts is alkaline ocean-island basalt comprehensively studied in the Uimon zone of Gorny Altai and Chara zone of Eastern Kazakhstan. This suggests active plume magmatism in the Early Paleozoic evolution of the Paleoasian Ocean. As inferred from sutures with high-pressure rocks, different parts of Paleoasian Ocean were closing successively.

We propose a model of the geodynamic evolution of the Dzhida island-arc system of the Paleoasian Ocean margin which records transformation of an oceanic basin into an accretion-collision orogenic belt. The system includes several Vendian-Paleozoic complexes that represent a mature oceanic island arc with an accretionary prism, oceanic islands, marginal and remnant seas, and Early Ordovician collisional granitoids. We have revealed a number of subunits (sedimentary sequences and igneous complexes) in the complexes and reconstructed their geodynamic settings. The tectonic evolution of the Dzhida island-arc system comprises five stages: (1) ocean opening (Late Riphean); (2) subduction and initiation of an island arc (Vendian-Early Cambrian); (3) subduction and development of a mature island arc (Middle-Late Cambrian); (4) accretion and formation of local collision zones and remnant basins (Early Ordovician-Devonian); and (5) postcollisional strike-slip faulting (Carboniferous-Permian).

Based on a comparative study of geochemistry of metavolcanics and metasediments of two large terranes, Baikal-Muya and Khamar-Daban-Ol'khon, as well as of the Baikal-Patom passive margin and Olokit accretionary wedge, we have recognized volcanosedimentary series accumulated in the settings of island arcs of different maturities and fragments of volcanosedimentary complexes of back-arc and fore-arc basins. Metabasalts of the Medvezhy and Tyya Formations in the basement of passive-margin sequence and the Olokit Group are similar in geochemistry to plateau basalts and mark the beginning of rifting on the platform periphery. The abundance of metavolcanics and turbidites in the Olokit Group permits this structure to be considered an accretionary wedge of the Baikal-Muya island arc. According to the metavolcanics composition, the Baikal-Muya terrane formed in the environment of oceanic ensimatic island arcs and back-arc and inter-arc basins with the minimum amounts of sediments and contains ophiolite slices. The geochemistry of metavolcanics and metasediments of the Ol'khon, Talanchan, and Slyudyanka complexes evidences their formation in the environment of ensialic back-arc sediment-rich basin (Slyudyanka, Ol'khon, and Svyatoi Nos series), mature island arc (Anga-Talanchan paleoarc, Anga and Talanchan Groups), and fore-arc basin (Khangarul' Group). According to chemistry and evolution history, all these complexes must be assigned to the Khamar-Daban-Ol'khon terrane.

Geochemical and geochronological studies of the main types of granitoids of the Angara-Vitim batholith (AVB) and granites of the Zaza complex in western Transbaikalia were carried out. U-Pb (SHRIMP-II) and Rb-Sr dating yielded the age of autochthonous gneiss-granites of the Zelenaya Griva massif (325.3 ± 2.8 Ma), quartz syenites of the Khangintui pluton (302.3 ± 3.7 Ma) and intruding leucogranites of the Zaza complex (294.4 ± 1 Ma), monzonites of the Khasurta massif (283.7 ± 5.3 Ma), and quartz monzonites of the Romanovka massif (278.5 ± 2.4 Ma). The U-Pb and Rb-Sr dates show that the Late Paleozoic magmatism in western Transbaikalia proceeded in two stages: (1) 340-320 Ma, when predominantly mesocratic granites of the Barguzin complex, including autochthonous ones, formed, and (2) 310-270 Ma, when most AVB granitoids formed. We suggest that at the early stage, crustal peraluminous granites formed in collision geodynamic setting. At the late (main) stage, magmatism occurred in postorogenic-extension setting and was accompanied by the formation of several geochemical types of granitoids: (1) typical intrusive mesocratic granites of the Barguzin complex, similar to those produced at the first stage; (2) melanocratic granitoids (monzonitoids, quartz syenites), which were earlier dated to the early stage of the AVB evolution; (3) leucocratic medium-alkali (peraluminous) granites of the Zaza intrusive complex; and (4) some alkali-granite and syenite intrusions accompanied by alkaline mafic rocks. The diversity of granitoids that formed at the late stage of magmatism was due to the heterogeneous composition of crust protoliths and different degrees of mantle-magma participation in their formation.

The Erdenet-Ovoo magmatic center (EOMC) lies within the North Mongolian magmatic area formed through the interaction of a Permo-Triassic plume with the lithosphere in an environment of active continental margin. Two stages are recognized in the EOMC history: subduction stage with participation of basalt-andesite-dacite-rhyolite series and rifting stage with trachybasalt series. The granitoid magmatism (258-220 Ma) is expressed as the Selenge, Shivota, and ore-bearing porphyry complexes. The formation of the Selenge and Shivota granitoids was preceded by the intrusion of gabbroids. Trachybasalts formed during the granitoid magmatism after the Selenge complex, nearly synchronously with the Shivota and ore-bearing porphyry complexes. At the subduction stage of the EMC evolution, the plume influence is documented from the appearance of gabbros both depleted and enriched in lithophile trace elements similar to volcanic rocks of trachybasalt series and basaltoids of bimodal series in northern Mongolia. The Rb-Sr and Sm-Nd isotope characteristics of the enriched gabbros suggest the participation of a lower mantle source in their formation. The plume, as a heat carrier, led to a large-scale manifestation of volcanism and, obviously, a wide development of basic rocks of this stage at depth. The basic rocks were the source of granitoid magma that produced the Selenge granitoids. The protolith melted in the >50 km thick crust preventing the wide manifestation of basaltoid volcanism in that period. The increased plume influence, rifting, uplift of the region, and extension of the crust favored the basaltoid and granitoid (Shivota and ore-bearing porphyry) magmatism activity.

Isotopic compositions of He (27 samples) and Ar (7 samples) as well as major and trace elements have been determined in Cenozoic effusive rocks and hosted olivine and pyroxene phenocrysts from northern and central Mongolia. The R = ³He/⁴He values are within (0.1-13) · 10^-6. Abnormally high R value, 13 · 10^-6, atypical of Cenozoic basaltic-volcanism areas in Mongolia, has been first revealed at one of the sites of the Hangayn upland. In composition the rocks under study correspond to tephrites, trachybasalts, and subalkalic andesite-basalts. Analysis of their REE patterns and spidergrams shows that the elements participating in the formation of basalt fields of the Hangayn upland were supplied from the enriched mantle (EM1). These patterns are similar to the OIB ones; (La/Yb) _n = 9-53. The R values in the olivine phenocrysts are higher as compared with the pyroxene phenocrysts and the bulk rock compositions of the same samples. Based on the elemental composition of the rocks, their contents of radiogenic ⁴He and ³He were calculated. The rate of ³He formation is 5.65 · 10^-2 at/(g · year). The calculated and measured R values in the rock samples point to the presence of trapped mantle helium.

The study was inspired by information on Paleozoic andesites, dacites, and diabases in Bel'kov Island in the 1974 geological survey reports used to reconstruct the tectonic evolution of the continental block comprising the New Siberian Islands and the bordering shelf. We did not find felsic volcanics or Middle Paleozoic intrusions in the studied area of the island. The igneous rocks are mafic subvolcanic intrusions, including dikes, randomly shaped bodies, explosion breccias, and peperites. They belong to the tholeiitic series and are similar to Siberian traps in petrography and trace-element compositions, with high LREE and LILE and prominent Nb negative anomalies. The island arc affinity is due to continental crust contamination of mantle magma and its long evolution in chambers at different depths. The 252±5 Ma K-Ar biotite age of magmatism indicates that it was coeval to the main stage of trap magmatism in the Siberian craton at the Permian-Triassic boundary. The terrane including the New Siberian Islands occurred on the periphery of the Siberian trap province where magmatism acted in a rifting environment. Magma intruded semiliquid wet sediments at shallow depths, shortly after their deposition. Therefore, the exposed Paleozoic section in Bel'kov Island may include Permian or possibly Lower Triassic sediments, of younger ages than it was believed earlier.

The Borgulikan ore field is localized in the west of the Umlekan-Ogodzha volcanoplutonic belt made up of various igneous (upper-Amur granite-granodiorite (140-134 Ma), Burunda monzodiorite-granodiorite (130-127 Ma), and Taldan andesite (127-123 Ma)) and superposed (Early Cretaceous Gal'ka trachybasalt-rhyolite (119-115 Ma) and Late Cretaceous trachybasalt-trachyandesite (97-94 Ma)) complexes. ⁴⁰Ar/³⁹Ar dating of porphyry intrusions breaking through the Taldan volcanic complex and associated with Cu-Mo-(Au) mineralization yielded the following ages: early (dark)

The paper summarizes paleomagnetic and rock-magnetic data on the Late Cretaceous diatremes and associated dikes from the Minusa trough located within the southwestern Siberian Platform. It is shown that the stable characteristic component of magnetization is superimposed magnetization (in physical sense). It is linked to Fe-rich titanomagnetite produced by the decay and oxidation of Ti-rich titanomagnetite derived from a primary magma. This process, however, coincides in time with the intrusion cooling, which is supported by paleomagnetic tests. Correlation of magnetic polarity with ³⁹Ar/⁴⁰Ar ages suggests that the acquired stable characteristic component of magnetization corresponds to magnetic Chrons C33-C32 and characterizes the Middle Campanian magnetic field (74-82 Ma). The mean paleomagnetic pole for this span is located at 82.8

We discuss main tectonic features of the Little Qinling gold belt in Central China, located along the northern border of the eastern Qinling E-W tectonic zone, which hosts hydrothermal lode gold deposits. The distribution of deposits and the strike of ore bodies are controlled by the Dayueping-Jinluoban anticlinorium and the related faults, namely large ductile-shear faults on its flanks striking parallel to the uplift axis and some large faults in the north and south. Mineralization is associated with smaller-scale mylonite zones of brittle-ductile deformation. The Dayueping-Jinluoban dome went through several stages of tectonic evolution (compression → folding → doming → strike-slip faulting → extensional faulting → reshearing) accompanied by regional deformation, metamorphism, migmatizition and mineralization.

We studied the 3D velocity structure of the crust and uppermost mantle beneath the Baikal region using tomographic inversion of ~25,000 P and S arrivals from more than 1200 events recorded by 86 stations of three local seismological networks. Simultaneous iterative inversion with a new source location algorithm yielded 3D images of P and S velocity anomalies in the crust and upper mantle, a 2D model of Moho depths, and corrections to source coordinates and origin times. The resolving power of the algorithm, its stability against variations in the starting model, and the reliability of the final results were checked in several tests. The 3D velocity structure shows a well-pronounced low-velocity zone in the crust and uppermost mantle beneath the southwestern flank of the Baikal rift which matches the area of Cenozoic volcanism and a high velocity zone beneath the Siberian craton. The Moho depth pattern fits the surface tectonic elements with thinner crust along Lake Baikal and under the Busiyngol and Tunka basins and thicker crust beneath the East Sayan and Transbaikalian mountains and under the Primorsky ridge on the southern craton border.

Analysis of the genetic relationship of Sn-bearing granitoids with ultrapotassic basic magmatism showed that their metallogeny was determined by the geochemistry of a specific reservoir localized in the continental lithosphere mantle (metasomatized mantle). The granitoid formation is well explained by the binary model of mixing of primary melts (products of the metasomatized mantle) with the continental crustal material. Geochemical studies of basic magmatism of different ages showed that the specific lithosphere reservoir formed in the Middle-Late Jurassic and existed at least till the late Late Cretaceous, i.e., during both tin metallogenic epochs of the Chukchi region.

A non-quadratic regularization algorithm modification is proposed. It ensures identifying and filtering angular spectrum false components by choosing regularizing functional parameters. The algorithm efficiency was proved by modeling while solving the problem of multibeam wavefield division using one input data realization.

Amplitude-phase representation of spatial group point objects given as quaternion signals is considered. The problem of estimating the rotation parameters and sequencing the point marks incorporated in a group object is solved. The obtained results allow using the matched filtering algorithm to solve the problem of recognizing spatial group point objects with unknown parameters of rotation and numbering of points in the object.

Methods for estimating the integral characteristics of electron microscope image periodograms, based on Hartley transform, Q-transform, and cosine transform, are proposed. It is shown that the cosine transform is more appropriate for filtering and improvement of psychophysical image perception on its basis. Various approaches to implementing matched filtering via cosine transform are considered. A procedure of electron microscope image decomposition with the use of various orthogonal transforms and filters based on Fourier patterns of Gauss and Morle wavelets is proposed and studied. It is shown that electron microscope image structure analysis using scalograms of orthogonal image transforms is promising

A measure of assessment of uncontrolled space image classification by a clustering technique based on a multivariate histogram is proposed. The measure is used to choose the best vector partitions corresponding to different detail of data representation. It is experimentally shown that well-separated unimodal clusters of the partitions correspond to representative information classes of a sensed land cover.

The data on the microelement composition of Siberian larch (Larix sibirica Ledeb.) growing in the Olkhon region

Seeding qualities and content of general and protein nitrogen in the seeds of Siberian spruce (Picea obovata Ledeb.), pine (Pinus sylvestris L.), Siberian larch (Larix sibirica L.) and Gmelin larch (Larix gmelinii Rupr.) from different regions of East Siberia were determined. It was revealed that the seeds of pine contain the highest level of total and protein nitrogen; the same seeds demonstrated the best seeding properties. A high correlation was found between the potential germination of the seeds of conifers under investigation and total nitrogen content in them. It was shown that the seeding qualities of the seeds and their nitrogen content vary depending on the region of seed collecting and exhibit an essential correlation with the mean July temperature in the regions and with the length of vegetative season.

The influence of environmental factors on the annual growth of crown organs (current year shoots and needles) of Scotch pine from Predbaikal forest-steppe zone was studied during 1976

The data on the understory renewal and analysis of height-age structure of maple (Acer platanoides L.) under the conditions of the Bashkir PreUrals (Ufa plateau) are reported on the basis of field research (during the years 1999

The data on the dynamics of diversity parameters for the grass suffruticous synfolium of the bilberry pine forest in the vicinity of the Reft electric power station are reported. Investigation showed that even with weakly expressed negative changes in parameters, as a rule, the dose

The polyvariation reality of response characteristics of balsam poplar (Populus balsamifera L.) on the sharp increase in metal concentration in the environment was established. It was shown that the metals stipulate changes in breath of poplar leaves. Is was shown that under the action of K⁺, Na⁺,

The state of winter dormancy and release for some evergreens, semi- and deciduous woody and shrubby plants growing under the natural and anthropogenic conditions in the Republic of Altay were investigated by means of recording fast and delayed fluorescence of chlorophyll. It was shown that the degree of winter dormancy, the rate of release and stability to thermal stress are the informative indices for early diagnostics of the injury of plants with industry-related emissions and biological indication of the level of environmental pollution in the region. It was noted that the brown colour of the leaves of Daurian rhododendron in winter has the adaptive importance.

Representative regions of cedar plantations were revealed in different height-belt complexes of the Borus ridge (the northern part of the Zapadny Sayan Ridge). Test grounds were settled with sampling the model trees according to the differentiated procedure checked in the Sayan-Shusha reserve. A retrospective analysis of seminiferous characteristics and the growth of female shoots of Siberian cedar was carried out. The dynamics of seminiferity was determined for the cedar forests growing under different ecological conditions. A less expressed amplitude of productivity over years is characteristic of the under-cliff taiga cedar growth. A possible dependence of the next-year productivity on the growth of the shoots of female generative stage was analyzed: a substantial development of the female generative stage is observed during the year preceding a good crop.

The species of epiphytic lichens on bark of Mongolian and dentate oaks in the south of Khasan region (Primorsky Territory) were investigated. The list of lichens includes 67 species, 55 of which are registered on Mongolian oak and 42 occur on dentate oak. On the basis of the distribution of species on lichen plots, the analysis of paired floristic similarity of lichen plots was carried out. Two graphic models which reflect the structure of lichen groups on both species of oaks were constructed.

Microbial communities of the thermal alkaline spring Seya (the Barguzin valley, North Pri-Baikalia) are investigated. Physicohcemical parameters of the medium, species and structural-functional composition of microbial mates are determined. The dependence of production processes and diversity of phototrophic organisms on physicochemical conditions is demonstrated, first of all on temperature and hydrogen sulphide content. Production processes go on most actively at a temperature of 30

Study relating to changes in the physiological state of Duschekia fruticosa (Rupr) Pouzar buds and content of stilbene growth-inhibiting substances (pinosylvin and its monomethyl ether) in the annual cycle of its development was made. It is shown that the processes of day length shortening from early to mid-August and water level decrease in cells cause the state of true dormancy for axillary buds of Duschekia fruticosa growing in Central Yakutia. Pinosylvin and its monomethyl ether are stored in buds in the course of inhibition of growth processes. During true dormancy, the content of pinosylvin monomethyl ether in young bud leaves comes to maximal values (50

Variability of the flavonoid content in 30 individual plants of Artemisia dracunculus L. during 5 years (1998

The high explanatory potential of Brown-Blanke method for the investigation of biological diversity of plants was demonstrated for the forests of two reserves of the Republic of Bashkortostan as examples. The method allows one to establish the types of plant communities of different ranks in the most formalized manner and to estimate on this basis beta diversity of specific territories, as well as absolute and relative synthetic alpha diversity of the communities. It was shown that higher relative synthetic alpha diversity of the communities of forests of Zhulgan-Tash reserve is a reason of higher gamma diversity, in spite of the fact that this reserve possesses smaller area and smaller hyperspace of environmental conditions in comparison with the Bashkyr reserve.

The diversity of life forms of Siberian rowan in the forest and under-cliff belts in the mountains of the Kuznetsky Alatau is investigated. Seven life forms of Siberian rowan were described. It was shown that the character and width of the biomorphological spectrum of the species are determined by the ecological cenotic conditions of the habitat. On the basis of an

For 32 North-Asiatic species of 6 sections of Euphorbia genus, the features of cyathia arrangement in general inflorescence, such as quantity, arrangement and branching of inflorescence axes were studied. The differences between inflorescences of different species were established. The features of the general inflorescence structure were revealed, which have important diagnostic value on different taxonomical levels in the system of genus, such as differentiation of terminal umbel, number of rays of the umbel and axillary rays, number of secondary rays and degree of branching, etc. A key for the diagnostics of the studied species of Euphorbia using inflorescence features was worked out and short characteristics of inflorescences in each species were listed.

The possibility of effective application of a plasma technology to decompose the molybdenum sulphate concentrate, molybdenite, is under consideration. First, the model system MoS_2- N₂ and then the real concentrate underwent the thermodynamic analysis. It has been shown that in the case of the real system which contains quite a few carbon (~26 %), initial feedstock decomposes through a stage of refractory molybdenum carbide

Results of an experimental study of the ignition dynamics of propane-air premixed flows under pulsed-periodic laser irradiation are reported. Ignition of homogeneous flows emanating into free atmosphere is considered. A comparative analysis of experimental and predicted delay times for the ignition for a medium at rest is given.