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V. A. San’kov A. V. Parfeevets A. V. Lukhnev A. I. Miroshnichenko S. V. Ashurkov 《Geotectonics》2011,45(5):378-393
Comprehensive analysis of the parameters characterizing contemporary and neotectonic deformations of the Earth’s crust and
upper mantle developed in the Mongolia-Siberia area is presented. The orientation of the axes of horizontal deformation in
the geodetic network from the data of GPS geodesy is accepted as an indicator of current deformations at the Earth’s surface.
At the level of the middle crust, this is the orientation of the principal axes of the stress-tensors calculated from the
mechanisms of earthquake sources. The orientation of the axes of stress-tensors reconstructed on the basis of structural data
is accepted as an indicator of Late Cenozoic deformations in the upper crust. Data on seismic anisotropy of the upper mantle
derived from published sources on the results of splitting of shear waves from remote earthquakes serve as indicators of deformation
in the mantle. It is shown that the direction of extension (minimum compression) in the studied region coincides with the
direction of anisotropy of the upper mantle, the median value of which is 310–320° NW. Seismic anisotropy is interpreted as
the ordered orientation of olivine crystals induced by strong deformation owing to the flow of mantle matter. The observed
mechanical coupling of the crust and upper mantle of the Mongolia-Siberia mobile area shows that the lithospheric mantle participated
in the formation of neotectonic structural elements and makes it possible to ascertain the main processes determining the
Late Cenozoic tectogenesis in this territory. One of the main mechanisms driving neotectonic and contemporary deformations
in the eastern part of the Mongolia-Siberia area is the long-living and large-scale flow of the upper mantle matter from the
northwest to the southeast, which induces both the movement of the northern part of the continent as a whole and the divergence
of North Eurasia and the Amur Plate with the formation of the Baikal Rift System. In the western part of the region, deformation
of the lithosphere is related to collisional compression, while in the central part, it is due to the dynamic interaction
of these two large-scale processes. 相似文献
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San’kov V. A. Lukhnev A. V. Parfeevets A. V. Miroshnichenko A. I. Ashurkov S. V. 《Doklady Earth Sciences》2011,436(1):159-164
The complex analysis of parameters characterizing the modern deformations of the Earth’s crust and upper mantle in the territory
of the Mongolia-Siberian Area is made. Directions of principal tension axes of stress-tensors, calculated with the use of
earthquake source mechanisms have been taken as parameters of modern deformations at the level of the middle crust; directions
of axes of horizontal strains in the geodesic network by the GPS data have been taken as such parameters at the level of the
Earth’s surface. The strain parameters for the mantle depths are the data on seismic anisotropy derived from the published
sources about the results of studies on splitting of transversal waves from distant earthquakes. Seismic anisotropy is interpreted
as the ordered orientation of olivine crystals, which appears with great strains resulting from the flow of the mantle material.
It has been shown that directions of extensional strain axes (minimal compression) by geodesic and seismological data coincide
with anisotropy directions in the upper mantle in the region whose median value is 310°–320°. The observed mechanical coupling
of the crust and the upper mantle of the Mongolia-Siberian Mobile Area shows the participation of the lithospheric mantle
in the formation of neotectonical structures and enables us to distinguish the principal processes determining the Late Cenozoic
tectogenesis in this territory. One of the leading mechanisms for the neotectonical and modern deformations of the Mongolia-Siberian
Region is the large-scale NW-SE material flow in the upper mantle causing both motion of the entire northern part of the continent
and divergence of the Eurasia and the Amurian Plate. Lithospheric deformations in the western part of the region are related
to collision-induced compression, while those in the central part are caused by interaction of these large-scale tectonic
processes. 相似文献
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The Cenozoic paleostress state of the Earth’s crust at the southwestern flank of the Baikal Rift System (Tunka system of basins) is reconstructed. With allowance for known facts about the geologic history of the Tunka system of basins, the evolution of the stress field and its formation conditions are established by comparison of the obtained reconstructions, including the dated stress fields, with the Pleistocene-Holocene deformations in active fault zones and the present-day stress state (seismotectonic deformations calculated from the focal mechanisms of earthquakes). The opening of basins in the NW-SE direction was proceeding in the transtensional regime from the Oligocene to the late Miocene or early Pliocene. At the early-late Pliocene boundary, this process was followed by the transpressional regime with compression in the NW direction. In the late Pliocene, the situation at the southwestern flank changed drastically. Since that time, deformation has occurred in the transpressional regime and the compression axis has been oriented in the NE direction. The alternative models of the evolution of the Tunka system of basins—oblique extension, the transform fracture zone, or a pull-apart system—are considered. Both models are combined in the framework of the suggested stress-field reconstruction. The oblique extension (transtension) was related to the early stages of evolution, whereas a possibility of forming pull-apart basin was existent at the late stages. 相似文献
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The paper addresses the Late Cenozoic fault tectonics and the stress state of the Earth’s crust within the Mongolian microplate,
embracing Central and Western Mongolia. We analyze the results of reconstructing the stress fields and the tectonic deformations
in the zones of active faulting, located at the uplands and in the intermountain trenches, which bound the microplate (Mongolian
Altai; Gobi Altai; Dolinoozersk trough; Khan-Taishir-Nuruu, Khan-Houkhei, and Bolnai uplands) and the Khangai dome. Deformations
related with the northeastern general-scale collisional compression are concentrated along the periphery of the Mongolian
microplate, and the maximum compression is focused on its western and southern boundaries, thus forming the right- and the
left-lateral transpressive structures of the Mongolian and Gobi Altai. The deformations associated with the shortening of
the Earth’s crust involve not only the mountain ridges framing the block, but also the intermountain troughs that separate
the Gobi and Mongolian Altai from the Khangai dome, and the southern portion of the Khangai Uplift. The diversity in the deformations
within the central Khengai region ensues from the coupling of tension caused by the dynamical impact of the mantle anomaly,
which is located east of 100°E, with a regional NE compression. Owing to the relatively rigid Khangai block, the deformations
are transferred to the northern bound of this structure, namely the seismically active North Khangai fault. The role of compression
increases to the west of the zone, where it conjugates with the transpressive structures of the Mongolian Altai. The tension
becomes more important in the western part of this zone where the releasing bends are formed. A region characterized by extra
tension is localized also to the east of 100° E. In terms of the gradient in the lithosphere thickness and the structure types
of the upper crust, the submeridional line running along 100°E is interpreted as the key interblock boundary. 相似文献
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