6 results on '"Petrunin, A.G."'
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2. Thickness of sediments in the Congo basin based on the analysis of decompensative gravity anomalies
- Author
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Kaban, M.K., Delvaux, D., Maddaloni, F., Tesauro, M., Braitenberg, C., Petrunin, A.G., El Khrepy, S., Tectonics, Tectonics, Kaban, M. K., Delvaux, D., Maddaloni, F., Tesauro, M., Braitenberg, C., Petrunin, A. G., and El Khrepy, S.
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010504 meteorology & atmospheric sciences ,Inversion (geology) ,Fragmentation (computing) ,Geology ,Structural basin ,Congo basin ,Decompensative gravity anomaly ,Sediments ,Upper crust ,010502 geochemistry & geophysics ,01 natural sciences ,Gravity anomaly ,Tectonics ,Basement (geology) ,Lithosphere ,Sediment ,Sedimentary rock ,Geomorphology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
The Congo basin is one of the largest intracratonic basins in the World, locating within a cold lithospheric plate. The structure of the thick sedimentary layer is investigated by seismic studies only in limited places. Here, we present a map of sedimentary thickness for the whole Congo basin, based on the inversion of the decompensative gravity anomalies. Contrary to the conventional Bouguer or isostatic gravity anomalies, the effect of the isostatic compensation of sediments is reduced in the decompensative anomalies, which provides a possibility to recover the full effect of low-density sediments. The calculated decompensative correction reaches ±70 mGal and exceeds the amplitude of the isostatic anomalies, especially in the long wavelengths. The final decompensative anomalies are negative over the whole basin and their patterns well correspond to its tectonic fragmentation. By inverting these anomalies with the predefined density-depth relationship we have obtained the sedimentary thickness map for the whole Congo basin. The maximum basement depth exceeding 10 km is found in the Lokoro basin and basins in the South. In the Lomami basin, thickness of sediments reaches about 6.5 km. It is important to note, that these deep depressions, are not covered by seismic studies. Furthermore, we found a new deep basin adjacent to the Lokonia High (on the SW side) that we propose to name as the Salonga basin.
- Published
- 2021
3. Strength variations of the Australian continent: Effects of temperature, strain rate, and rheological changes
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Tesauro, M., Kaban, M.K., Petrunin, A.G., Aitken, A.R.A., Tectonics, Tectonics, Tesauro, M., Kaban, M. K., Petrunin, A. G., and Aitken, A. R. A.
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Effective Elastic Thickne ,010504 meteorology & atmospheric sciences ,02 engineering and technology ,Yilgarn Craton ,Oceanography ,01 natural sciences ,Thermal Model ,Lithosphere ,0202 electrical engineering, electronic engineering, information engineering ,Australian Lithosphere ,Crustal Rheology ,Effective Elastic Thickness ,Strength Model ,Petrology ,0105 earth and related environmental sciences ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,020206 networking & telecommunications ,Crust ,Strain rate ,Craton ,Tectonics ,Seismic tomography ,Intraplate earthquake ,Geology - Abstract
The Australian continent is composed of several geologic provinces, showing a general age progression from Archean in the west to Phanerozoic in the east. The lithospheric heterogeneity and complex tectonic history of this region make it a key area for studying the thermal and rheological structure of the geological provinces and testing the influence of different conditions, such as temperature, rheology, and strain rate on the plate strength. In a previous study, temperature and compositional variations of the Australian upper mantle have been determined based on a joint interpretation of the seismic tomography and gravity data. In this study, we further implement a thermal model of the crust, based on available surface heat flow data from regional and global database. The crustal and upper mantle thermal models show different anomalies distribution, indicating a significant variation of the thermal conditions with depth. The new thermal models are used to estimate strength and effective elastic thickness (Te) distribution in the lithosphere. For this aim, we assigned the rheology of the crust based on the seismic velocities provided by the AuSREM model and used the strain rate values obtained from a global mantle flow model, constrained by seismic and gravity data. The maximal strength and Te are found in the West Australian Craton, on account of the low temperatures in the lithospheric mantle. We found that locations of the intraplate earthquakes attend to sharp changes in the lithospheric strength. Comparison of the results with those obtained for uniform rheology and strain rate, indicate that in the Officer basin the variations of the crustal rheology enhance the effect of temperature changes, while in the Yilgarn craton they reduce it. On the other hand, the lower values of the strain rate in the cratons than in the Phanerozoic regions influence the strength/Te in the opposite way with respect to temperatures.
- Published
- 2020
4. Strength and elastic thickness variations in the Arabian Plat: A combination of temperature, composition and strain rates of the lithosphere
- Author
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Tesauro, M., Kaban, Mikhail K., Petrunin, A.G., El Khrepy, S., Al-Arifi, N., Tectonics, Tectonics, Tesauro, Magdala, Kaban, Mikhail K., Petrunin, Alexey G., El Khrepy, Sami, and Al-Arifi, Nassir
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010504 meteorology & atmospheric sciences ,media_common.quotation_subject ,Plate ,Inversion (geology) ,Geometry ,Rigidity (psychology) ,010502 geochemistry & geophysics ,01 natural sciences ,Asymmetry ,Strength and effective elastic thickness of the lithosphere ,Physics::Geophysics ,Gravitational field ,Lithosphere ,Shield ,Lithospheric structure ,Geophysic ,0105 earth and related environmental sciences ,media_common ,Earth-Surface Processes ,Arabian Plate ,Strain rate variations ,Geophysics ,Arabian ,Tectonics ,Seismic tomography ,Strain rate variation ,Geology - Abstract
The Arabian Plate shows a strong asymmetry between its Shield and Platform, in terms of topography, seismic velocity and density structure of the upper mantle. This asymmetry also results in significant rheological differences between these blocks, as revealed by the effective elastic thickness (EET) estimates, obtained using a spectral gravity method. However, these estimates may be biased due to various factors: therefore, other approaches based on a direct rheological modeling of the lithospheric structure should be employed to verify these results. In this study, we use a recent model of the lithosphere, based on an integrative interpretation of the gravity field and seismic tomography, to correct an initial thermal model obtained from the inversion of seismic velocity, assuming a uniform composition. The results are used together with the most recent crustal model of the Arabian Plate to construct two alternative models of strength and EET of the lithosphere. The first model (Model I) assumes a constant value of 10− 15 s− 1 for the strain rates. In the second model (Model II), we used the strain rates obtained from a global mantle flow model. Model I confirms the asymmetry in the rigidity of the Shield and Platform. In contrast, Model II shows that the influence of the variable strain rates causes a significant increase in the strength and EET of the central and eastern part of the Shield and in contrast to previous studies, reveals that most of the Arabian Plate is a long-term stable tectonic feature, predominantly characterized by large EET values (≥ 70 km). Do you want to read the rest of this article?Request full-text Strength and elastic thickness variations in the Arabian Plate: A combination of temperature, composition and strain rates of the lithosphere. Available from: https://www.researchgate.net/publication/314832634_Strength_and_elastic_thickness_variations_in_the_Arabian_Plate_A_combination_of_temperature_composition_and_strain_rates_of_the_lithosphere [accessed Apr 18, 2017].
- Published
- 2018
5. Siberian meimechites: origin and relation to flood basalts and kimberlites.
- Author
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Sobolev, A.V., Sobolev, S.V., Kuzmin, D.V., Malitch, K.N., and Petrunin, A.G.
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ULTRABASIC rocks ,FLOOD basalts ,LAVA flows ,KIMBERLITE ,PETROLOGY ,ANALYTICAL geochemistry - Abstract
Abstract: Here we combine petrological-geochemical and thermomechanical modeling techniques to explain origin of primary magmas of both Maimecha–Kotui meimechites and the Gudchikhinskaya basalts of Norilsk region, which represent, respectively, the end and the beginning of flood magmatism in the Siberian Trap Province. We have analyzed the least altered samples of meimechites, their olivine phenocrysts, and melt inclusions in olivines, as well as samples of dunites and their olivines, from boreholes G-1 and G-3 within the Guli volcanoplutonic complex in the Maimecha–Kotui igneous province of the northern Siberian platform. The Mn/Fe and Ni/MgO ratios in olivines indicate a mantle peridotite source of meimechites. Meimechite parental magma that rose to shallow depths was rich in alkalis and highly magnesian (24 wt.% MgO), largely degassed, undersaturated by sulfide liquid and oxidized. At greater depths, it was, likely, high in CO
2 (6 wt.%) and H2 O (2 wt.%) and resulted from partial melting of initially highly depleted and later metasomatized harzburgite some 200 km below the surface. Trace-element abundances in primary meimechite magma suggest presence of garnet and K-clinopyroxene, in the mantle source and imply for genetic link to the sources of the early Siberian flood basalts (Gudchikhinskaya suite) and kimberlites. The analyzed dunite samples from the Guli complex have chemistry and mineralogy indicating their close relation to meimechites. We have also computed thermomechanical model of interaction of a hot mantle plume with the shield lithosphere of variable thickness, using realistic temperature- and stress-dependent visco-elasto-plastic rocks rheology and advanced finite element solution technique. Based on our experimental and modeling results we propose that a Permian–Triassic plume, with potential temperature of about 1650 °C transported a large amount of recycled ancient oceanic crust (up to 15%) as SiO2 -supersaturated carbonated eclogite. Low-degree partial melting of eclogite at depths of 250–300 km produced carbonate-silicate melt that metasomatized the lithospheric roots of the Siberian shield. Further rise of the plume under relatively attenuated lithosphere (Norilsk area) led to progressive melting of eclogite and formation of reaction pyroxenite, which then melted at depths of 130–180 km. Consequantly, a large volume of melt (Gudchikhinskaya suite) penetrated into the lithosphere and caused its destabilization and delamination. Delaminated lithosphere that included fragments of locally metasomatized depleted harzburgite subsided into the plume and was heated to the temperatures of the plume interior with subsequent generation of meimechite magma. Meimechites showed up at the surface only under thicker part of the lithosphere aside from major melting zone above because otherwise they were mixed up in more voluminous flood basalts. We further suggest that meimechites, uncontaminated Siberian flood basalts and kimberlites all shear the same source of strongly incompatible elements, the carbonated recycled oceanic crust carried up by hot mantle plume. [Copyright &y& Elsevier]- Published
- 2009
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6. Three-dimensional numerical models of the evolution of pull-apart basins
- Author
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Petrunin, A.G. and Sobolev, S.V.
- Subjects
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GEOLOGICAL basins , *STRUCTURAL geology , *EVOLUTIONARY theories , *GEODYNAMICS , *GEOLOGIC faults , *MATHEMATICAL models , *CRUST of the earth , *EARTH (Planet) - Abstract
Abstract: Pull-apart basins are depressions that form as the result of crustal extension along strike-slip systems where the sense of fault stepping or bending coincides with that of fault slip. They are common features of strike-slip systems. We perform a number of numerical thermomechanical experiments to explore how the rheology of the lithosphere influences basin evolution and lithospheric structure beneath the basin. Our modeling shows that basin subsidence results from the competition of extension of the brittle part of the lithosphere, which leads to its subsidence, and of the compensating flow of the deeper ductile part of the lithosphere, which pushes the extended brittle block upwards. The result of this competition is the subsidence rate. Strain partitioning beneath the basin and crustal structures is controlled by (i) the thickness of the brittle layer and basin width, (ii) the magnitude of strike-slip displacement, (iii) the rate of frictional softening of the crust, and (iv) the viscosity of the ductile part of the lithosphere. The thickness of the brittle layer and the viscosity of the underlying ductile part of the lithosphere in turn depend on temperature, composition and material softening. We interpret the modeling results, deducing simple analytical expressions based on the “brittle brick stretching” (BBS) approach, which despite its simplicity describes the structure and evolution of pull-apart basins reasonably well. We also demonstrate that the structure and evolution of the Dead Sea Basin, located at a left step of the Dead Sea Transform in the Middle East, is consistent with a BBS type of deformation with only a minor contribution from compensational flow in the ductile part of the lithosphere. Finally, we show that the formation of a deep narrow pull-apart basin in relatively cold lithosphere, as in the Dead Sea Basin, requires very low friction at major faults (lower than 0.1–0.2). If this condition is not satisfied, strike-slip deformation does not localise and deep basins do not form. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
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