共查询到20条相似文献,搜索用时 215 毫秒
1.
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
2.
Yu. L. Rebetsky 《Russian Journal of Pacific Geology》2009,3(5):477-490
The field of modern tectonic stresses was reconstructed for the Earth’s crust of the northwestern segment of the Pacific subduction
zones. For this purpose, we used the method of cataclastic analysis and data on the magnitude of the stresses released at
the source of the Simushir earthquake of 2006, which allowed us to determine both the orientation of the principal stress
axes and the magnitude of the stresses and to estimate the effective strength of rock masses. The effective cohesion was estimated
for this region of the Earth’s crust as 12 bar, and the maximum shear stresses are no higher than 300 bar. The analysis of
the reconstructed stress field in the zone of the preparation of the Simushir earthquake showed that this region was almost
free of domains with high stresses where brittle failure requires considerable energy inputs. The medium level of effective
pressure indicates that this region is most favorable for the development of a large-scale brittle failure. 相似文献
3.
The paper reports results of the analysis of the spatial distribution of modern (younger than 2 Ma) volcanism in the Earth’s
northern hemisphere and relations between this volcanism and the evolution of the North Pangaea modern supercontinent and
with the spatial distribution of hotspots of the Earth’s mantle. Products of modern volcanism occur in the Earth’s northern
hemisphere in Eurasia, North America, Greenland, in the Atlantic Ocean, Arctic, Africa, and the Pacific Ocean. As anywhere
worldwide, volcanism in the northern hemisphere of the Earth occurs as (a) volcanism of mid-oceanic ridges (MOR), (b) subduction-related
volcanism in island arcs and active continental margins (IA and ACM), (c) volcanism in continental collision (CC) zones, and
(d) within-plate (WP) volcanism, which is related to mantle hotspots, continental rifts, and intercontinental belts. These
types of volcanic areas are fairly often neighboring, and then mixed volcanic areas occur with the persistent participation
of WP volcanism. Correspondingly, modern volcanism in the Earth’s northern hemisphere is of both oceanic and continental nature.
The latter is obviously related to the evolution of the North Pangaea modern supercontinent, because it results from the Meso-Cenozoic
evolution of Wegener’s Late Paleozoic Pangaea. North Pangaea in the Cenozoic comprises Eurasia, North and South America, India,
and Africa and has, similar to other supercontinents, large sizes and a predominantly continental crust. The geodynamic setting
and modern volcanism of North Pangaea are controlled by two differently acting processes: the subduction of lithospheric slabs
from the Pacific Ocean, India, and the Arabia, a process leading to the consolidation of North Pangaea, and the spreading
of oceanic plates on the side of the Atlantic Ocean, a process that “wedges” the supercontinent, modifies its morphology (compared
to that of Wegener’s Pangaea), and results in the intervention of the Atlantic geodynamic regime into the Arctic. The long-lasting
(for >200 Ma) preservation of tectonic stability and the supercontinental status of North Pangaea are controlled by subduction
processes along its boundaries according to the predominant global compression environment. The long-lasting and stable subduction
of lithospheric slabs beneath Eurasia and North America not only facilitated active IA + ACM volcanism but also resulted in
the accumulation of cold lithospheric material in the deep mantle of the region. The latter replaced the hot mantle and forced
this material toward the margins of the supercontinent; this material then ascended in the form of mantle plumes (which served
as sources of WP basite magmas), which are diverging branches of global mantle convection, and ascending flows of subordinate
convective systems at the convergent boundaries of plates. Subduction processes (compressional environments) likely suppressed
the activity of mantle plumes, which acted in the northern polar region of the Earth (including the Siberian trap magmatism)
starting at the latest Triassic until nowadays and periodically ascended to the Earth’s surface and gave rise to WP volcanism.
Starting at the breakup time of Wegener’s Pangaea, which began with the opening of the central Atlantic and systematically
propagated toward the Arctic, marine basins were formed in the place of the Arctic Ocean. However, the development of the
oceanic crust (Eurasian basin) took place in the latter as late as the Cenozoic. Before the appearance of the Gakkel Ridge
and, perhaps, also the oceanic portion of the Amerasian basin, this young ocean is thought to have been a typical basin developing
in the central part of supercontinents. Wegener’s Pangaea broke up under the effect of mantle plumes that developed during
their systematic propagation to the north and south of the Central Atlantic toward the North Pole. These mantle plumes were
formed in relation with the development of global and local mantle convection systems, when hot deep mantle material was forced
upward by cold subducted slabs, which descended down to the core-mantle boundary. The plume (WP) magmatism of Eurasia and
North America was associated with surface collision- or subduction-related magmatism and, in the Atlantic and Arctic, also
with surface spreading-related magmatism (tholeiite basalts). 相似文献
4.
Robert Tenzer Pavel Novák Peter Vajda Vladislav Gladkikh Hamayun 《Computational Geosciences》2012,16(1):193-207
We developed and applied a novel numerical scheme for a gravimetric forward modelling of the Earth’s crustal density structures
based entirely on methods for a spherical analysis and synthesis of the gravitational field. This numerical scheme utilises
expressions for the gravitational potentials and their radial derivatives generated by the homogeneous or laterally varying
mass density layers with a variable height/depth and thickness given in terms of spherical harmonics. We used these expressions
to compute globally the complete crust-corrected Earth’s gravity field and its contribution generated by the Earth’s crust.
The gravimetric forward modelling of large known mass density structures within the Earth’s crust is realised by using global
models of the Earth’s gravity field (EGM2008), topography/bathymetry (DTM2006.0), continental ice-thickness (ICE-5G), and
crustal density structures (CRUST2.0). The crust-corrected gravity field is obtained after modelling and subtracting the gravitational
contribution of the Earth’s crust from the EGM2008 gravity data. These refined gravity data mainly comprise information on
the Moho interface and mantle lithosphere. Numerical results also reveal that the gravitational contribution of the Earth’s
crust varies globally from 1,843 to 12,010 mGal. This gravitational signal is strongly correlated with the crustal thickness
with its maxima in mountainous regions (Himalayas, Tibetan Plateau and Andes) with the presence of large isostatic compensation.
The corresponding minima over the open oceans are due to the thin and heavier oceanic crust. 相似文献
5.
We developed a simple algorithm allowing automated generation of map slices and cross sections from discrete values of geological
and geophysical parameters described by 3D data sets. The data input and output were handled in the standard formats of Word,
DOS, and the Surfer 8 package, which make it possible to be widely used by small scientific and technical teams in the processing
of geological information and the interpretation of local GISs. The practical implementation of the proposed algorithm is
exemplified by the study of the density properties in the Earth’s crust and upper mantle of Transbaikalia and Sikhote-Alin. 相似文献
6.
V. B. Kaplun 《Russian Journal of Pacific Geology》2012,6(2):131-142
The results of magnetotelluric sounding along the 350-km long Blagoveshchensk-Birakan profile are discussed. The profile begins
in the Longjiang-Selemdzha orogenic belt and ends in the Jiamusi-Bureya massif, thus intersecting the southern Amur-Zeya sedimentary
basin from the northwest to the southeast. Twelve soundings have been performed in the broad range from 1 × 104 to 2 × 10−4 Hz. Geoelectric sections have been constructed for the depths of 2 and 150 km with the determination of the geoelectric parameters
of the sedimentary cover within the basin and the identification of the zones of anomalous conductivity in the Earth’s crust
and upper mantle. 相似文献
7.
B. Homuth U. Löbl A. G. Batte K. Link C. M. Kasereka G. Rümpker 《International Journal of Earth Sciences》2016,105(6):1681-1692
Shear-wave splitting measurements from local and teleseismic earthquakes are used to investigate the seismic anisotropy in the upper mantle beneath the Rwenzori region of the East African Rift system. At most stations, shear-wave splitting parameters obtained from individual earthquakes exhibit only minor variations with backazimuth. We therefore employ a joint inversion of SKS waveforms to derive hypothetical one-layer parameters. The corresponding fast polarizations are generally rift parallel and the average delay time is about 1 s. Shear phases from local events within the crust are characterized by an average delay time of 0.04 s. Delay times from local mantle earthquakes are in the range of 0.2 s. This observation suggests that the dominant source region for seismic anisotropy beneath the rift is located within the mantle. We use finite-frequency waveform modeling to test different models of anisotropy within the lithosphere/asthenosphere system of the rift. The results show that the rift-parallel fast polarizations are consistent with horizontal transverse isotropy (HTI anisotropy) caused by rift-parallel magmatic intrusions or lenses located within the lithospheric mantle—as it would be expected during the early stages of continental rifting. Furthermore, the short-scale spatial variations in the fast polarizations observed in the southern part of the study area can be explained by effects due to sedimentary basins of low isotropic velocity in combination with a shift in the orientation of anisotropic fabrics in the upper mantle. A uniform anisotropic layer in relation to large-scale asthenospheric mantle flow is less consistent with the observed splitting parameters. 相似文献
8.
A possible mechanism of the ascent of material within the Earth’s crust and mantle is the mechanism of hydroextrusion, i.e.,
the effect of squeezing of material under excess pressure. The major factors that predetermine the high plasticity of the
material and its ability to produce hydroextrusions are high lithostatic pressures and temperatures. The phenomenon of hydroextrusion
can be most clearly illustrated by the example of the origin of salt diapirs. The driving force of hydroextrusions of material
in the crust and mantle is excess pressure, which can result from lateral differences between the densities of rocks (as is
the case during the development of salt diapirs) and phase transitions associated with a volume increase. When the material
of the upper mantle undergoes partial melting with the derivation of basaltic melts at depths of 60–100 km, excess pressures
reach 80 MPa, whereas the plasticity limit of 20% melted rocks is no higher than 5 MPa. As a result, the partially molten
material is forced from the melting region toward zones with lower lithostatic pressures. A local temperature increase in
the transitional zones in the Earth’s mantle at positive dP/dT values of the phase transitions also gives rise to excess pressures, whose values can range from 100 to 800 MPa at a 0.5–3.0%
volume change and which can be the driving force during the origin of mantle plumes.
Original Russian Text ? V.N. Anfilogov, Yu.V. Khachai, 2006, published in Geokhimiya, 2006, No. 8, pp. 873–878. 相似文献
9.
According to their genesis, meteorites are classified into heliocentric (which originate from the asteroid belt) and planetocentric
(which are fragments of the satellites of giant planets, including the Proto-Earth). Heliocentric meteorites (chondrites and
primitive meteorites genetically related to them) used in this study as a characteristic of initial phases of the origin of
the terrestrial planets. Synthesis of information on planetocentric meteorites (achondrites and iron meteorites) provides
the basis for a model for the genesis of the satellites of giant planets and the Moon. The origin and primary layering of
the Earth was initially analogously to that of planets of the HH chondritic type, as follows from similarities between the
Earth’s primary crust and mantle and the chondrules of Fe-richest chondrites. The development of the Earth’s mantle and crust
precluded its explosive breakup during the transition from its protoplanetary to planetary evolutionary stage, whereas chondritic
planets underwent explosive breakup into asteroids. Lunar silicate rocks are poorer in Fe than achondrites, and this is explained
in the model for the genesis of the Moon by the separation of a small metallic core, which sometime (at 3–4 Ga) induced the
planet’s magnetic field. Iron from this core was involved into the generation of lunar depressions (lunar maria) filled with
Fe- and Ti-rich rocks. In contrast to the parent planets of achondrites, the Moon has a olivine mantle, and this fact predetermined
the isotopically heavier oxygen isotopic composition of lunar rocks. This effect also predetermined the specifics of the Earth’s
rocks, whose oxygen became systematically isotopically heavier from the Precambrian to Paleozoic and Mesozoic in the course
of olivinization of the peridotite mantle, a processes that formed the so-called roots of continents. 相似文献
10.
The kinetics of hydrogen diffusion in enstatite was studied by hydrogen–deuterium exchange experiments in the range of 1–5,000 bar and 700–850°C using synthetic single crystals of pure and Cr-doped enstatites. The OH- and OD-content in the samples was quantified after each thermal treatment with Fourier transformed infrared spectroscopy. H–D-exchange rates were measured parallel to the three crystallographic axes. In addition, in order to visualize diffusion profiles, OH and OD were mapped for some samples, utilizing synchrotron IR micro-spectroscopy. Hydrogen self-diffusivities derived from D/H exchange experiments at one atmosphere are very similar to the chemical diffusivity of hydrogen in natural Fe-bearing orthopyroxene, which was reported previously (Stalder and Skogby 2003) to exhibit a small, but significant anisotropy (D[001] > D[100] > D[010]). Activation energies are estimated to be 211 (±31) kJ/mol for diffusion parallel [100] and 185 (±28) kJ/mol for diffusion parallel [010]. Lattice diffusion of hydrogen is decelerated by more than one order of magnitude when Cr is dissolved in enstatite. In comparison to the chemical composition, pressure seems to have only a minor influence on hydrogen diffusion. Compared to other minerals in the Earth’s upper mantle, enstatite exhibits the highest activation energy for hydrogen diffusion, suggesting faster diffusion than in other mafic minerals at mantle temperatures, but slower diffusion at crustal conditions. Thus under upper mantle conditions, physical properties that are expected to be influenced by hydrogen mobility, such as electrical conductivity, may in enstatite be more intensely affected by the presence of hydrogen than in other upper mantle minerals. 相似文献
11.
青藏高原的隆升由印度-欧亚板块的碰撞而驱动,其生长演化,特别是从内到外的扩展机制仍尚存争议。祁连山地处青藏高原向东北扩展的前缘位置,其地壳结构与各向异性对于理解青藏高原向北扩展的生长机制具有重要意义。祁连山中部是青藏高原东北缘地壳遭受挤压强烈变形的区域,已有的研究已经揭示出地壳内部非耦合不均匀变形的几何行为,揭露其对应机制是亟待探索的前沿科学问题。此前该区域的各向异性研究大多基于面状台网数据,台站间距大,无法反映横跨祁连山地壳各向异性的精细变化。为此,本研究选用一条密集线性地震台阵,使用H-κ-c叠加方法,得到了横过祁连山中部的地壳厚度,泊松比以及地壳各向异性的横向变化。结果显示,在中祁连以及南祁连北部地壳厚度最大,平均泊松比最低,反映了地壳加厚过程中铁镁质下地壳的丢失以及长英质中上地壳的水平缩短。此外,偏长英质成分的泊松比值也不支持地壳流在该区域存在。在祁连山内部,地壳各向异性快波的偏振方向与地壳向外扩展方向一致,而与地幔各向异性快波方向近垂直,揭示了壳幔变形可能是解耦的。而在地壳较薄的南祁连和北祁连南部区域,快波方向与古缝合线的走向一致,说明早古生代的构造格局仍对现今的祁连山缩短隆升产生影响。 相似文献
12.
V. B. Piip 《Moscow University Geology Bulletin》2009,64(5):296-305
The paper discusses the mantle structure along superlong seismic profiles in Russia examined using the method of homogenous
functions. Two-dimensional heterogeneous sections of the upper mantle were calculated from travel-time curves to a depth of
500–600 km with allowance for the Earth’s curvature without using any a priory information. The presentation of sections as
surfaces with a shaded relief combined with velocity contours allowed discerning the principal interfaces in the lithosphere
and in the upper mantle, the internal structure of layers, and local heterogeneities of different shapes (convective cells
and slabs) in the sections. 相似文献
13.
L. N. Kogarko 《Geochemistry International》2006,44(1):3-10
Alkaline magmatism has occurred since 2.5–2.7 Ga and its abundance has continuously increased throughout the Earth’s history.
Alkaline rocks appeared on the Earth with changes in the geodynamic regime of our planet, i.e., when plume tectonics was supplemented
by plate tectonics. Global-scale development of plate tectonics at the Archean—Proterozoic boundary initiated subduction of
already significantly oxidized oceanic crust enriched in volatiles and large-scale mantle metasomatism caused the formation
of enriched reservoirs as sources of alkaline and carbonatite magmatism. Study of metasomatized mantle material showed the
occurrence of traces of primary carbonatite melts, which are strongly enriched in rare elements, according to ion-microprobe
analyses. The results obtained allowed us to propose a new two-stage genetic model for Ca-rich carbonatites including (1)
metasomatic wehrlitization and carbonatization of mantle material and (2) partial melting of wehrlitized mantle with formation
of carbonate-rich melts or three immiscible liquids (at high alkali contents), i.e., silicate, carbonatitic, and sulfide (at
high sulfur activity).
Original Russian Text L.N. Kogarko, 2006, published in Geokhimiya, 2006, No. 1, pp. 5–13. 相似文献
14.
During the Triassic collision of the Yangtze and Sino-Korean cratons, the leading edge of the Yangtze crust subducted to mantle depths and was subsequently exhumed as a penetratively deformed, coherent slab capped by a normal shear zone. This geometry requires a reverse shear zone at the base of the slab, and we suggest that the Yangtze foreland fold-and-thrust belt constitutes this zone. Lower Triassic rocks of the eastern foreland record NW–SE compression as the oldest compressional stress field; onset of related deformation is indicated by Middle Triassic clastic sedimentation. Subsequent Jurassic stress fields show a clockwise change of compression directions. Based on nearly coeval onset and termination of deformation, and on a common clockwise change in the principal strain/stress directions, we propose that the foreland deformation was controlled by the extrusion of the ultra high-pressure slab. Widespread Cretaceous–Cenozoic reactivation occurred under regional extension to transtension, which characteristically shows a large-scale clockwise change of the principal extension directions during the Lower Cretaceous. 相似文献
15.
Theoretical ideas based on the results of numerical modeling of mantle convection are presented. The thermochemical model
has taken into consideration such factors as two-layer structure of the mantle, formation of light substance in the D” layer
(owing to transition of metallic components into the core), and heavy substances in subduction zones (eclogite-alteration
of the oceanic crust). Numerical experiments have shown that this system allows phenomena of global mantle overturns, which
make possible to model the general pattern of the Earth’s geologic evolution. The suggested theory establishes cause-effect
relationships in the sequence of geological events and is conformed to all the empirical data. 相似文献
16.
Tuna Eken Jaroslava Plomerová Roland Roberts Ludek Vecsey Vladislav Babuška Hossein Shomali Reynir Bodvarsson 《Tectonophysics》2010,480(1-4):241-258
Body-wave analysis — shear-wave splitting and P travel time residuals — detect anisotropic structure of the upper mantle beneath the Swedish part of Fennoscandia. Geographic variations of both the splitting measurements and the P-residual spheres map regions of different fabrics of the mantle lithosphere. The fabric of individual mantle domains is internally consistent, usually with sudden changes at their boundaries. Distinct backazimuth dependence of SKS splitting excludes single-layer anisotropy models with horizontal symmetry axes for the whole region. Based upon joint inversion of body-wave anisotropic parameters, we instead propose 3D self-consistent anisotropic models of well-defined mantle lithosphere domains with differently oriented fabrics approximated by hexagonal aggregates with plunging symmetry axes. The domain-like structure of the Precambrian mantle lithosphere, most probably retaining fossil fabric since the domains' origin, supports the idea of the existence of an early form of plate tectonics during the formation of continental cratons already in the Archean. Similarly to different geochemical and geological constraints, the 3D anisotropy modelling and mapping of fabrics of the lithosphere domains contribute to tracking plate tectonics regimes back in time. 相似文献
17.
Yuan Xuecheng 《《地质学报》英文版》1989,63(3):211-225
Through recent study, the author considers that the north-south-trending Kangding-Honghe tectonic belt is not a marginal uplift zone of the Yangtze Platform but a Tethyan-type collisional tectonic belt of which the crust-upper mantle can be structurally divided into three layers. The upper layer is the brittle upper crust, dominated by overthrusting and imbrication; the middle layer is the plastic lower crust and part of the upper mantle, represented by compression and shortening; and the lower layer is the upper mantle, probably belonging to the Yangtze Platform in light of the thickness of the lithosphere. 相似文献
18.
Tectonics,stress state,and geodynamics of the Mesozoic and Cenozoic Rift basins in the Baikal region
The results of geological, structural, tectonic, and geoelectric studies of the dry basins in the Baikal Rift Zone and western
Transbaikalia, combined under the term Baikal region, are integrated. Deformations of the Cenozoic sediments related to pulsing
and creeping tectonic processes are classified. The efficiency of mapping of the fault-block structure of the territories
overlapped by loose and poorly cemented sediments is shown. The faults mapped at the ground surface within the basins are
correlated with the deep structure of the sedimentary fill and the surface of the crystalline basement, where they are expressed
in warping and zones of low electric resistance. It is established that the kinematics of the faults actively developing in
the Late Cenozoic testifies to the relatively stable regional stress field during the Late Pliocene and Quaternary over the
entire Baikal region, where the NW-SE-trending extension was predominant. At the local level, the stress field of the uppermost
Earth’s crust is mosaic and controlled by variable orientation of the principal stress axes with the prevalence of extension.
The integrated tectonophysical model of the Mesozoic and Cenozoic rift basin is primarily characterized by the occurrence
of mountain thresholds, asymmetric morphostructure, and block-fault structure of the sedimentary beds and upper part of the
crystalline basement. The geological evolution of the Baikal region from the Jurassic to Recent is determined by alternation
of long (20–115 Ma) epochs of extension and relatively short (5.3–3.0 Ma) stages of compression. The basins of the Baikal
Rift System and western Transbaikalia are derivatives of the same geodynamic processes. 相似文献
19.
A. A. Stepashko 《Russian Journal of Pacific Geology》2010,4(3):228-241
It is shown that the deep structure of the lithosphere played a decisive role in the recent deformations and seismicity in
the Far East. The regional variations in the composition of the mantle xenoliths and Neogene-Quaternary basalts provided grounds
for mapping the NE-extending wedge-shaped block of the Fe-rich mantle at the base of Sikhote Alin. Its boundaries continue
the Yilan-Yiton and Fushun-Mishan strike-slip faults of the Tan-Lu zone, along which this mantle block was displaced along
the continental margin in the Jurassic-Cretaceous. The localization of strong (M ≥ 5.0) earthquake epicenters in the Amur
region shows that such a mantle structure determines the key features of the regional deformations and seismotectonics. Under
the dominant western compression due to the Amur Plate’s motion, the mantle wedge is extruded in the northeastern direction
to provide an additional stress at the Okhotsk Plate boundary. This process resulted in the formation of the Sakhalin high-seismicity
zone at the front of the mantle block. In its characteristics, the zone is similar to the convergence area between the Indian
and Eurasian plates. In both cases, the main deformation and seismicity features were caused by the horizontal pressure of
the tectonic block, the frontal part of which is marked by regularly alternating compression and extension zones. In Sakhalin,
strong earthquakes with M ≥ 6.0 are confined to the seismic suture 50 km wide with concentrated compression. This structure
is discordant relative to the main faults of the island, being parallel to the front of the mantle wedge. The two migration
cycles established for the Sakhalin earthquakes with M ≥ 6.0 correspond to periods of 1907–1971 and 1995–2007. During both
cycles, the first shocks occurred in the north and subsequently migrated in the southeastern direction simultaneously decreasing
in the depths of the earthquake foci. The systematic migration implies that asymmetrical compression is responsible for both
the extrusion of the mantle wedge and its southeastward clockwise rotation. The latter plays the decisive role in the initiation
of strong earthquakes on Sakhalin. 相似文献
20.
A. P. Sorokin V. B. Kaplun Yu. F. Malyshev A. T. Sorokina 《Doklady Earth Sciences》2011,439(2):1084-1087
The Zeya-Bureya Basin is a part of the East Asian intracontinental riftogenic belt, which includes oil-and-gas bearing and
Mesozoic-Cenozoic sedimentary basins perspective for oil and gas (Upper Zeya, Songliao, Liaohe, North Chinese). The basins
are characterized by certain geophysical features: reduced thickness of the Earth’s crust and lithosphere, a higher thermal
flow and a raised roof of the asthenosphere. The Zeya-Bureya Basin is composed of Mesozoic-Cenozoic sedimentary-volcanic units,
with respect to which the deep structure data are absent. In 2010, geoelectric studies were carried out in this territory
using the method of magnetotelluric sounding along the profile Blagoveshchensk-Birokan. These works yielded geoelectric sections
down to 2 and 200 km depth. The sedimentary cover is characterized by electric resistivity of 20–50 Ohm m and by thickness
of 1700 m. In the section, the Khingan-Olonoi volcanogenic trough is distinct for resistivity of 200–300 Ohm m at a background
of 500–1000 Ohm m of the basement rocks. The Zeya-Bureya Basin, in terms of its geophysical characteristics, differs from
oil-and-gas bearing basins of the riftogenic belt (thickness of the lithosphere is increased up to 120 km, thermal flow is
low, 40–47 mW/m2). The structure of mantle underplating is explicitly seen in the section. The geophysical characteristics close to those
of the Zeya-Bureya Depression are typical for gold-bearing structures of the Lower Amur ore district. Nevertheless, manifestations
of oil-and-gas bearing potential in particular grabens are possible. 相似文献