Home – Home – Jornals – Contemporary Problems of Ecology 2008 number 4

This paper reviews available the mantle plume models and formulates seven questions, which can be solved using geological and geochemical data in terms of the thermochemical plume model.
The main features of thermochemical plumes, including calculated plume parameters, are presented. It has been estimated how the power of a plume depends on water concentration in melt at variable melt portions and diffusion coefficients (Lewis numbers). A correlation between the latter and temperature drop at the base of a plume has been shown.
The obtained plume parameters are compared with model plume localities, such as the Hawaiian and East African plumes, Siberian and Emeishan flood basalts, etc. Based on the oceanic plate movement pattern and He, Os, and Sr isotope data, the Hawaiian plume was proved to be generated within the D₂ lower mantle layer; the diameter of the plume channel is about 100 km, the plume channel rotated and migrated to 100-200 km every 2 Ma; the plume power is about 3 · 10⁸ kW, changing each 15 Ma. The reconstruction of complex core material-plume melts and Layer C-asthenosphere interactions is possible only by isotopic data and primary olivine composition.
The plume model was applied to large igneous provinces (Siberian, Emeishan, and Ontong Java LIPs) using detailed mechanisms of plume head interaction with the lithosphere. Taking into account the similar age and evolution of the Tunguska syncline (Siberian LIP) and West Siberia, the plume-lithosphere interactions are deduced from the relationships between sedimentary and magmatic units, different modes of rifting, and variations of Sr and Nd isotopes.

The paper reports data on the age, composition, and geodynamic environments of Permian ultramafic-mafic complexes in the Zaisan-Gobi zone in the eastern Gobi-Tien Shan rift belt. The synchronous formation of these complexes with Early Permian lava alkali and tholeiitic basalts discovered beneath the cover of the Tarim and Junggar platform blocks suggests that they are derivates of the Tarim plume related to the Permo-Triassic Siberian superplume. This is evidenced from the composition and metallogeny of the complexes similar to those of magnesian trap intrusions on the western periphery of the Siberian Platform.
In the area of influence of the Tarim plume, including the Zaisan-Gobi zone and other structures of the Gobi-Tien Shan belt, diverse Cu-Ni-PGE, Ni-Co-As, Au-Hg, Cu-Mo, and ore deposits related to plume magmatism formed. Their composition, formation conditions, and relationship with magmatism are discussed.

New structural and petrological data have been obtained for the zone of Siberia-Kazakhstan oblique collision for Permian time. In terms of classical tectonics, the area coincides with the Zaisan folded area produced by closure of the Char paleo-ocean in the Late Carboniferous. However, the extent, structure, and composition of magmatism at the Carboniferous-Permian (280 ± 10 Ma) and Permian-Triassic (250 ± 5 Ma) boundaries require an active control from Morgan-type lower mantle plumes (Tarim and Siberian plumes). Structure formation in the lithosphere and heat sources of magmatism have been simulated in a 3D model including lithospheric strain rates (with regard to viscosity layering) and subcontinental upper mantle convection. According to our model, heat supply from slab break-off and/or delamination of lithosphere is insufficient to maintain large-scale mantle-crustal magmatism in the case of oblique collision between 80-100 km thick plates (

We have shown that the occurrences of Permo-Triassic magmatism in northern Vietnam compose the southwestern and southeastern flanks of the Emeishan large igneous province, shifted along the large-amplitude Ailao Shan-Red River shear zone. Based on new geochronological (U-Pb and Ar/Ar) data, two stages of magmatism related to the Emeishan plume have been recognized. At the first, Permian, stage (260 Ma), abundant picritoids of the Song Da and Song Hien zones formed, and at the second, gabbro-syenite and gabbro-monzodiorite associations of the Lo Gam zone, layered peridotite-gabbro massifs of the Nui Chua complex, high-alumina granites of the Phia Bioc complex, and basalt-rhyolite association of the Song Hien zone were produced. The metallogenic specialization of the Permo-Triassic magmatism of northern Vietnam is considered.

We investigate the dynamics of multilevel subcontinental melting beneath a lithosphere of variable thickness as a model simulating generation of melts that produced flood basalt in the Siberian Trap province. The inferred sequence of volcanic events correlates with upper mantle decompression melting above hotspots and related conductive melting of metasomatized depleted lithosphere. Numerical experiments show that complex mafic magmatic systems of this kind are at least two-stage with a zone of decompression melting in upwelling mantle flow and a sub-Moho lithospheric melting region; the shallower lithospheric melting region can be disconnected from the mantle zone of decompression melting along the edges of the magmatic system; the lithospheric melting region has a particular layered structure with its top at a depth of 60-70 km and a maximum size exceeding the length of the erupted lava field; mafic melts produced at different levels of the system have different compositions.

Geological, petrological, geochemical, and isotope data from the Yenisei Ridge indicate three stages of rifting and attendant within-plate magmatism at 750, 700, and 670 Ma. The igneous rocks of the three stages are, respectively, metarhyolite-basalt, trachybasalt-trachyte, and alkali ultramafic (alkali picrite) associations. Magmatism was concurrent with terrigenous deposition of the Neoproterozoic Upper Vorogovka, Chingasan, and Chapa Groups. The volcanosedimentary complexes were deposited in narrow rift-like graben along faults. The earlier consolidated flanking uplifts of the graben experienced granitoid magmatism synchronously with rifting and within-plate volcanism. The respective plutonic events produced granitoid intrusions of the Ayakhta (760-750 Ma), Kutukas (690-700 Ma), and Middle Tatarka (~700 Ma) alkaline complexes, and the later (about 650-670 Ma) alkali ultramafic Chapa complex of carbonatites and metasomatites. Basalts and alkaline rocks are chemically similar to ocean-island and continental-rift basalts which have been reliably attributed to mantle plumes. Neoproterozoic rifting and within-plate magmatism were possibly related to the plume activity responsible for the breakup of Rodinia. These events in the Yenisei Ridge appear to be coeval with rifting and within-plate magmatic processes in other continental blocks which may have been parts of the Rodinia supercontinent.

We investigated local geology of Meso-Cenozoic basalt complexes in the Tien Shan and collected the first samples that represent nearly the entire area of within-plate basaltic magmatism in Central Asia (over 285,000 km²). According to their ⁴⁰Ar/³⁹Ar ages, the Tien Shan basalts erupted for a relatively short time span between 61 and 76 Ma, in the Late Cretaceous-Paleogene. The trace- and rare-earth-element compositions of rocks show that most of the studied basaltic series in the Tien Shan formed in within-plate magmatic systems related to mantle plume sources. Some melts bear evidence of crustal contamination. The compositions of melt inclusions and patterns of trace and rare-earth elements in them are consistent with the plume origin of the melts and with the evolution of magmatic systems toward an increase in K, Al, and Fe contents. The melt inclusion data show a direct dependence of the crystallization temperatures of parental melts of the Meso-Cenozoic Tien Shan basalts on their Mg#: 1220-1250

We report new isotope dates and metallogenic and chemical characteristics of granitoids from the Hangayn area (central Mongolia) with implications for the time and tectonic settings of their formation. Proximal U-Pb and Ar-Ar ages of 241.3 ± 1.5 Ma and 238.2 ± 2.5 Ma have been obtained for the Triassic Guchin Us and Hurmen Gol intrusions, respectively, and an Early Permian age (288.7 ± 2.3 Ma, Ar-Ar) for the Bayanulaan granite and for granite porphyry from the Saran Uul Cu-Mo-(Au) deposit. Granitoids of the Egiyn Davaa, Hangayn, and Shar Us Gol complexes in the southwestern Hangayn area are of two geochemical types. Some intrusions that were formerly attributed to these complexes have been reinterpreted as resulting from multiple plutonic pulses of different ages. According to our new data and published evidence, most of granitoids in the area may have been produced by Early-Middle Triassic (255-230 Ma) rather than Permian and Late Triassic-Early Jurassic events. The Hangayn granitoids are of low mineral potential. Gold mineralization in the area is confined within the Hangayn gold belt and appears to be independent of the intrusions.

In the 1980s, Ag-Sb deposits were discovered in a new ore cluster of the Delyun-Yustyd back-arc rift basin in southeastern Altai and northwestern Mongolia. The Delyun-Yustyd basin is filled with up to 9 km thick Devonian volcanosedimentary and terrigenous rocks lying over Vendian-Cambrian carbonate-terrigenous strata. Volcanosedimentary rocks are intruded by D₃-C₁ granites of the Yustyd complex, as well as by pre-granite mafic rocks, post-granite gabbro-diabase, diabase porphyry dikes, and younger lamprophyre dikes of the Chuya complex (245-236 Ma Ar-Ar biotite age). Ag-Sb ores in the Yustyd cluster formed at the Early Mesozoic stage at 240 ± 1.6 Ma (Early-Middle Triassic boundary) and were thus nearly coeval with the Chuya lamprophyre intrusion. The age of Cu-Ag-Sb-Hg mineralization is about 234.4 ± 1.0 Ma (Ar-Ar, sericite). Sb-Hg mineralization is the latest in the province (231.5 ± 1.0 Ma, Ar-Ar, sericite). Gradual change of Ag-Sb (siderite-tetrahedrite) ores to complex Cu-Ag-Sb-Hg (Hg-Ag-tetrahedrite) and Sb-Hg (cinnabar with Sb sulfosalts and stibnite) mineralization along the Kurai-Kobdo and Terekta-Tolbonur large faults is interpreted as development of stage metallogenic zoning along major ore-controlling faults.

In connection with the problem of water bloom in continental water reservoirs due to cyanobacteriae, the effect of hydrophysical (wind strength, intensity of photosynthetically active radiation, and atmospheric precipitation) and geochemical factors (concentrations of the forms of nitrogen and mineral phosphorus in water) on the fluorescence characteristics of eukaryotic microalgae and cyanobacteriae characterized by different abilities to light-dependent regulation of floatage is investigated in the surface layer of a small eutrophic water reservoir Bugach in 2002.

Plant introduction is considered now as the most promising way of biodiversity preservation. Collections of the Botanical Garden of the Institute of Biololy KSC UD RAS contain over 3.5 thousand decorative plant taxa (species and varieties), of which about 150 species are rare and protected in various regions of Russia and neighboring countries. Among the arboreal plants growing in the arboretum, 26 taxa belong to rare and endangered species, of them 19 taxa are exotics and 7 are native species. Among the plants growing in a glasshouse, 7 arboreal species belong to rare and endangered ones, all being introduced from other floristic areas. The paper presents results of the studies on biomorphological features of rare species, plant mutability in the course of adaptation and plant reproduction capacity under new ecological conditions.

Ten populations of Ribes nigrum L. (black currant) in the basin of the Ingoda river were investigated. The description of black currant participated phytocoenosis in which the researched populations grow was carried out. The ecological and geographical characteristic of population habitats of currant black was given.

Two forms of Siberian apple tree were revealed in the Selenginsky region of Buryatia that are distinguished by stunting, ability to propagate by root shoots, natural growth as a bush, shortened interstitials, as well as high decorative properties. These lines represent a very interesting material for investigation (microevolution processes, investigation of the genetic and biological foundations of dwarf state, selection of dwarf stocks, and introduction).

A multi

The composition and comparative analysis of the partial floras of habitat types of the post-drag landscapes of the model basin of the Suenga river in the Salair mountain ridge is revealed and presented.

The data on the ecology of Rhododendron mucronulatum, Rh. sichotense and Rh. dahuricum, as well as the results of investigation of the flowering system structure in these species in 5 coenopopulations in the Primorsky region and Chita region are presented. Understanding of the ecological requirements and morphological structure of the studied species is very important for the development of cultivation technology and systematic position of Rhododendron L. In natural coenopopulations, Rh. mucronulatum blooms one-two weeks earlier than Rh. sichotense and Rh. dahuricum. However, under the conditions of Vladivostok, Rh. sichotense begins to flower earlier; Rh. dahuricum and Rh. mucronulatum start to bloom one week later.

On the basis of the an

When using a collection of published data concerning forest-forming species of the Ural and adjacent regions in a number of 1230 plots of forest biomass (stems, branches, foliage, roots and understory) and 245 plots of annual primary production, the regression equations are designed. The first-group equations describe the dependence of forest biomass upon mass-forming factors

The southern coastal Baikal Lake area is characterized by the dampest climate in the Baikal region, the basic amount of rain preci

The data on the variability of the plant community formation of the n

A detailed systematic list of subaquatic epilithic and aquatic lichens inhabiting the surf zone and the littoral region of the test site Cape Berezovyi (Southern Baikal) is provided on the basis of investigations carried out within the years 2002

An investigation of plant cover conditions in the north of Middle Siberia was carried out. The study was based on lichenological data. The article describes approaches and methods of lichenoindication of plant cover condition using the an

The results of river water monitoring at the licensed oil field areas in the Middle Ob area are presented. The complex estimation of the river water ecological conditions is made using microbiological indication and biotesting. The number of heterotrophic saprophytic bacteria in the majority of rivers correspond to the satisfactory water quality. The faecal pollution indicators were detected in most rivers. The self-purification potential of the major part of streams was low. The Gram-positive coccus bacterial forms were dominant in microbial cenosis in the majority of rivers. Seven toxic samples were detected using the biotesting.

Investigation of the faun

Under the conditions of the southern taiga in West Siberia, the highest level of seasonal catalase and anaerobic dehydrogenase activity of the forest reclaimed peat soil was revealed within the moisture content range 20

Two computer-aided algorithms of forest water protection zone allocation using the digital elevation model (DEM) and spatial an

The efficiency of photoluminescent (light-correcting) polymeric films on the enzymatic activity of microorganisms in oil-polluted soil was investigated under laboratory conditions. The effect of the use of films as a covering material containing organic and inorganic photoluminophores was studied under the UV-irradiation of the soil polluted with oil products in the concentration up to 50 g/kg. The application of light-correcting films increases the activtiy of enzymes in oil-polluted soil: catalase by a factor of 2

Accumulation of heavy metals in the system soil-plant caused by the application of increasing doses of sewage sediments under the conditions of Transbaikalia was considered. On the basis of the index of total pollution, an optimal dose of waste water sediments to be introduced was revealed. The use of sewage sediments that are accumulated in cities also solves the ecologically essential problem of sediment utilization.

The influence of heavy metal mobile forms on the number of ecological-trophical groups of microorganisms in the soil substratum of the placer gold mines in Priamurje is discussed. The investigated soil samples are characterized by stable enrichment with such elements as Co, Ni, Cr, Cu, Pb, Zn, As, Mo. The amount of mobile forms (with respect to total content) varies from 0.5 to 54 % depending on element. A dependence between the indices of pollution and the ranges of the number of main ecological-trophical groups of microorganism is revealed. Dependencies between increased concentrations of the mobile forms of some heavy metals and the microbiological indices are established and illustrated.

The pollution of the Amur river water with organic compounds at the Khabarovsk drinking water supply point is studied by means of gas chromatography

Diversity and the anatomic structure of the ectomycorrhizas of Siberian spruce in natural communities over the altitudinal gradient from 305 to 800 m above the sea level (northern taiga, the Denezhkin Kamen

A description of the system of ecological monitoring in the State Natural Reserve Stolby (Krasnoyarsk District) is presented. The degree of pollution of the ecosystems of the reserve with fluorine emitted by a high-capacity aluminium plant is determined.

Thermal radiation of forest fires of different kinds is investigated. The regions in which thermal radiation affects the forest stands and firemen are revealed.

Comparative investigation of the activity of li

The data on the important ecological feature of alder-tree

The method to account the rates of changes in relative humidity in one-years sprouts of coniferous wood plants is proposed. On the basis of the data of N. D. Nesterovich [1965], the account of the rates of humidity changes within one year is carried out for 8 coniferous wood plant species; the average relations of water content for a same month of each year is determined. The rates of changes in humidity within one year for one-years sprouts of coniferous wood plants are determined.

Pollen of 12 species of the Spiraea L. genus growing in differetn regions of Siberia and the Far East is investigated. The ultrasculpture of pollen grains is described. On the basis of aperture morphology and exine sculpture, the main types of pollen grains are sorted, and the key indices for their determination are revealed. It is noted that the species of the Spiraria section are distinguished by the large size of grains. Substantial variations of the size of pollen grains was established for S. media and S. alpina species. The level of natural polymorphism of palynological indices is shown.

203 species of vascular plants, 50 species of mosses and 41 species of lichens are found on gold mining sites. The list of these species is reviewed. The distribution over technogenic relief elements is indicated for each species. The main elements of the technogenic relief, their flora and vegetation are characterized. The species composition and ecological-coenological spectra of drag and hydraulic gun dumps are the most similar ones. The species diversity of vascular plants on gold mining sites is high in different regions.

The paper examines the results of the cluster analysis for 25 sections in the genus Oxytropis DC. on the basis of 50 quantitative alternative characters in morphology. It has mainly confirmed the division into subgenera and sections accepted by different investigators. It reveals the affinity (not identity) between subgenera Tragacanthopsis Vass. and Triticaria Vass. (difference: 44 %), and justifies the recognition of the section Chrysantha Vass. in the subgenus Oxytropis, as well as the recognition of the sections Dolichanthos Gontsch and Mongolia F. C. Fu, the latter being related to the subgenus Ptiloxytropis Bunge. In addition, unreasonableness of disjunction of the section Mesogaea Bunge off the Janthin

The paper presents the an