Paleoproterozoic,High-Metamorphic,Metasedimentary Units of Siberian Craton     

Lena URMANTSEVA  Olga TURKINA 《《地质学报》英文版》2009,83(5):875-883

Abstract: Sensitive, high-resolution ion microprobe zircon U–Pb ages of Paleoproterozoic, high-grade, metasedimentary rocks from the south-western part of the Siberian Craton are reported. Early Precambrian, high-grade complexes, including garnet–biotite, hypersthene–biotite, and cordierite-bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4–3.1 Ga indicate Archean-to-Paleoproterozoic source provinces. Zircons from gneisses show core-rim textures in cathodoluminescence (CL) image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are: ≥2.7, ~2.3, and 1.95–2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga; therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High-grade metaterrigenous sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the Aldan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga (Wan et al., 2006). All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high-grade metamorphism was related to the consolidation of the Siberian Craton.  相似文献   

Young circumnuclear disks in elliptical galaxies     

Olga K. Sil’chenko 《Astrophysics and Space Science》2009,320(1-3):51-54

By means of integral-field spectroscopy with the Multi-Pupil Field/Fiber Spectrograph of the Russian 6-m telescope we have studied the central parts of NGC 759 and NGC 83— regular (non-interacting, without strong nuclear activity) round red luminous (M _B =?20.8–?21.6) elliptical galaxies which are however known to possess molecular gas. In both galaxies we have found central stellar disks with the extension of 1–2 kpc along the radius which are evidently being formed just now.  相似文献   

On an application of cluster analysis for classification of valley cross profiles using special orthonormal functions     

Olga J. Waelder 《Central European Journal of Geosciences》2009,1(2):232-239

Morphometric approaches deal with obtaining quantitative parameters of relief forms. In particular, such parameters can be used for the classification of diverse relief forms. There is a noticeable demand for such approaches in geosciences. For example, the differentiation of valley forms belongs to the research field of geomorphology. A valley form includes important information with respect to the valley genesis. It is assumed that the U-shape probably corresponds to a glacier-induced valley, but the V-shape reflects the fluvial genesis of a valley. A prior generalisation of valley cross-profiles is necessary in order to obtain their morphometric parameters. These parameters contribute to the valley differentiation. The conventional generalisation approaches are based on the approximation of such cross-profiles using a special function. This function can be a catenary curve, a special polynomial or a set of polynomials. An alternative model is the GPL model. In this paper we propose a new generalisation approach, which uses special orthonormal functions. Based on these functions, form coefficients can be obtained for use in cluster analysis, resulting in the shape classification of valley cross profiles. An application of our approach for a real data set is presented.  相似文献   

Debris flow hazards for mountain regions of Russia: regional features and key events     

Perov  Veniamin  Chernomorets  Sergey  Budarina  Olga  Savernyuk  Elena  Leontyeva  Tatiana 《Natural Hazards》2017,88(1):199-235

The total area of debris flow territories of the Russian Federation accounts for about 10% of the area of the country. The highest debris flow activity areas located in Kamchatka-Kuril, North Caucasus and Baikal debris flow provinces. The largest debris flow events connected with volcano eruptions. Maximum volume of debris flow deposits per one event reached 500 × 10⁶ m³ (lahar formed during the eruption of Bezymyanny volcano in Kamchatka in 1956). In the mountains of the Greater Caucasus, the maximum volume of transported debris material reached 3 × 10⁶ m³; the largest debris flows here had glacial reasons. In the Baikal debris flow province, the highest debris flow activity located in the ridges of the Baikal rift zone (the East Sayan Mountains, the Khamar-Daban Ridge and the ridges of the Stanovoye Highland). Spatial features of debris flow processes within the territory of Russia are analyzed, and the map of Debris Flow Hazard in Russia is presented. We classified the debris flow hazard areas into 2 zones, 6 regions and 15 provinces. Warm and cold zones are distinguished. The warm zone covers mountainous areas within the southern part of Russia with temperate climate; rain-induced debris flows are predominant there. The cold zone includes mountainous areas with subarctic and arctic climate; they are characterized by a short warm period, the occurrence of permafrost, as well as the predominance of slush flows. Debris flow events are described for each province. We collected a list of remarkable debris flow events with some parameters of their magnitude and impact. Due to climate change, the characteristics of debris flows will change in the future. Availability of maps and information from previous events will allow to analyze the new cases of debris flows.  相似文献   

A simplified method for assessing landslide damage indices   总被引：1，自引：0，他引：1  

Olga Petrucci  Giovanni Gullà 《Natural Hazards》2010,52(3):539-560

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A Europe–South America network for climate change assessment and impact studies     

Jean-Philippe Boulanger  G. Brasseur  Andrea Fabiana Carril  Manuel de Castro  Nicolas Degallier  Carlos Ereño  H. Le Treut  Jose Antonio Marengo  Claudio Guillermo Menendez  Mario Nestor Nuñez  Olga C. Penalba  Alfredo Luis Rolla  Matilde Rusticucci  Rafael Terra 《Climatic change》2010,98(3-4):307-329

The goal of the CLARIS project was to build an integrated European–South American network dedicated to promote common research strategies to observe and predict climate changes and their consequent socio-economic impacts taking into account the climate and societal peculiarities of South America. Reaching that goal placed the present network as a privileged advisor to contribute to the design of adaptation strategies in a region strongly affected by and dependent on climate variability (e.g. agriculture, health, hydro-electricity). Building the CLARIS network required fulfilling the following three objectives: (1) The first objective of CLARIS was to set up and favour the technical transfer and expertise in earth system and regional climate modelling between Europe and South America together with the providing of a list of climate data (observed and simulated) required for model validations; (2) The second objective of CLARIS was to facilitate the exchange of observed and simulated climate data between the climate research groups and to create a South American high-quality climate database for studies in extreme events and long-term climate trends; (3) Finally, the third objective of CLARIS was to strengthen the communication between climate researchers and stakeholders, and to demonstrate the feasibility of using climate information in the decision-making process.  相似文献   

Effects of heavy metals on some soil biological parameters   总被引：11，自引：0，他引：11  

Olga Mikanova 《Journal of Geochemical Exploration》2006,88(1-3):220

The soils most polluted by heavy metals are probably alluvial soils. One of them is the alluvium of the Litavka River. The heavy metal content was much higher in some cases than the threshold values, allowed by the Czech standards. The effect of soil contamination on enzyme activity is presented. Generally, the values of enzymatic activities were highest in the soil above the source of contamination and they decrease as they approach the source of contamination. All measured parameters were affected by heavy metal concentrations. Our results demonstrate that several parameters of microbial activity could be used as good indicators of increasing concentrations of Cd, Pb and Zn in soil.  相似文献   

Non-monotone spectral projected gradient method applied to full waveform inversion   总被引：1，自引：0，他引：1  

Noam Zeev  Olga Savasta  Debora Cores 《Geophysical Prospecting》2006,54(5):525-534

The seismic inversion problem is a highly non‐linear problem that can be reduced to the minimization of the least‐squares criterion between the observed and the modelled data. It has been solved using different classical optimization strategies that require a monotone descent of the objective function. We propose solving the full‐waveform inversion problem using the non‐monotone spectral projected gradient method: a low‐cost and low‐storage optimization technique that maintains the velocity values in a feasible convex region by frequently projecting them on this convex set. The new methodology uses the gradient direction with a particular spectral step length that allows the objective function to increase at some iterations, guarantees convergence to a stationary point starting from any initial iterate, and greatly speeds up the convergence of gradient methods. We combine the new optimization scheme as a solver of the full‐waveform inversion with a multiscale approach and apply it to a modified version of the Marmousi data set. The results of this application show that the proposed method performs better than the classical gradient method by reducing the number of function evaluations and the residual values.  相似文献   

Forest Carbon Dynamics in the Pacific Northwest (USA) and the St. Petersburg Region of Russia: Comparisons and Policy Implications     

Ralph J. Alig  Olga Krankina  Andrew Yost  Julia Kuzminykh 《Climatic change》2006,79(3-4):335-360

Forests of the United States and Russia can play a positive role in reducing the extent of global warming caused by greenhouse gases, especially carbon dioxide. To determine the extent of carbon sequestration, physical, ecological, economic, and social issues need to be considered, including different forest management objectives across major forest ownership groups. Private timberlands in the U.S. Pacific Northwest are relatively young, well stocked, and sequestering carbon at relatively high rates. Forests in northwestern Russia are generally less productive than those in the Northwestern U.S. but cover extensive areas. A large increase in carbon storage per hectare in live tree biomass is projected on National Forest timberlands in the U.S. Pacific Northwest for all selected scenarios, with an increase of between 157–175 Mg by 2050 and a near doubling of 1970s levels. On private timberlands in the Pacific Northwest, average carbon in live tree biomass per hectare has been declining historically but began to level off near 65 Mg in 2000; projected levels by 2050 are roughly what they were in 1970 at approximately 80 Mg. In the St. Petersburg region, average carbon stores were similar to those on private lands in the Pacific Northwest: 57 Mg per hectare in 2000 and ranging from 40 to 64 Mg by 2050. Although the projected futures reflect a broad range of policy options, larger differences in projected carbon stores result from the starting conditions determined by ownership, regional environmental conditions, and past changes in forest management. However, an important change of forest management objective, such as the end of all timber harvest on National Forests in the Pacific Northwest or complete elimination of mature timber in the St. Petersburg region, can lead to substantial change in carbon stores over the next 50 years.  相似文献   

MOF/MUF behavior over one European path     

Olga A. Maltseva  B. G. Barabashov  V. T. Rodionova  A. S. Shlyupkin 《Acta Geophysica》2007,55(3):424-440

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