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E.?P.?DubininEmail author Yu.?I.?Galushkin A.?L.?Grokholskii A.?V.?Kokhan N.?M.?Sushchevskaya 《Geotectonics》2017,51(3):209-229
The paper describes the specific features of the bottom topography and morphostructural segmentation along the strike of the Southeast Indian Ridge (SEIR) and in the zones of influence of the Amsterdam–St. Paul hot spot and the anomalous zone of the relatively cold mantle in the area of the Australian–Antarctic discordance. Numerical estimates of changes of thermal state and strength of the crust in axial and off-axial zones of the SEIR were performed. Сorrelation between the thermal–rheological settings in the axial zone of the ridge with the seabed topography and the morphostructural segmentation and magmatism has been established. The numerical modelling results make it possible to assume the presence of along-axis asthenospheric flows under the axial zone of the SEIR. One of them, which was initiated by the Amsterdam–St. Paul point and the Kerguelen plume, is oriented from west to east, and the second, located east of the Australian–Antarctic discordance, is oriented from east to west. Taking into account the numerical modelling results of the thermal regime and the change in thickness of the brittle layer of the axial lithosphere, we performed a physical modelling of the influence of temperature anomalies in the mantle on the peculiarities of crustal deformation in the axial zones of the ridge. The experimental modelling showed that the presence of a thermal anomaly in the sublithosphere mantle in the form of a local heat source (hot spot) will noticeably influence the geometry of the rift axis and its position in relation to the hot spot. An area of anomalous topography forms under the influence of the hot spot, traces of which are preserved in the off-axis spreading flank zones, as in the case of the Amsterdam–St. Paul hot spot. More contrasting and dissected topography forms in zones with a relatively low typical mantle temperature in the process of crustal accretion. 相似文献
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Zayonchek A. V. Brekke H. Sokolov S. Yu. Ermakov A. V. Efimov V. N. Zaraiskaya Yu. A. Akhmedzyanov V. R. Kalinin N. D. Kokhan A. V. Moroz E. A. Ol’shanetskii D. M. Razumovskii A. A. Yampol’skii K. P. 《Doklady Earth Sciences》2010,430(2):265-270
Doklady Earth Sciences - 相似文献
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The rift zone??s relief, the spreading kinematics, and the experimental modeling of the Knipovich Ridge??s formation were analyzed. Its rift zone is formed in a transtension environment. Faulting is predominant in its northern part, while strike-slip is characteristic for the south. A system of short extension basins connected by deep strike-slip U-shaped troughs is observed in the south. A system of volcanic rises connected by short shallow basins is observed in the north. The rift valley is V-shaped. According to the experimental modeling data, these extension kinematics provide the formation of short extension basins connected by strike-slips and transtension faults. Their length and orientation depend on the spreading obliquity of each segment. 相似文献
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The tectonics, structure-forming processes, and magmatism in rift zones of ultraslow spreading ridges are exemplified in the Reykjanes, Kolbeinsey, Mohns, Knipovich, Gakkel, and Southwest Indian ridges. The thermal state of the mantle, the thickness of the brittle lithospheric layer, and spreading obliquety are the most important factors that control the structural pattern of rift zones. For the Reykjanes and Kolbeinsey ridges, the following are crucial factors: variations in the crust thickness; relationships between the thicknesses of its brittle and ductile layers; width of the rift zone; increase in intensity of magma supply approaching the Iceland thermal anomaly; and spreading obliquety. For the Knipovich Ridge, these are its localization in the transitional zone between the Gakkel and Mohns ridges under conditions of shear and tensile stresses and multiple rearrangements of spreading; nonorthogonal spreading; and structural and compositional barrier of thick continental lithosphere at the Barents Sea shelf and Spitsbergen. The Mohns Ridge is characterized by oblique spreading under conditions of a thick cold lithosphere and narrow stable rift zone. The Gakkel and the Southwest Indian ridges are distinguished by the lowest spreading rate under the settings of the along-strike variations in heating of the mantle and of a variable spreading geometry. The intensity of endogenic structure-forming varies along the strike of the ridges. In addition to the prevalence of tectonic factors in the formation of the topography, magmatism and metamorphism locally play an important role. 相似文献
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E. P. Dubinin A. L. Grokhol’skii A. V. Kokhan A. A. Sveshnikov 《Izvestiya Physics of the Solid Earth》2011,47(7):586-599
Specific features of the bottom topography structure and the character of morphostructural segmentation of the rift zone of
the Reykjanes Ridge change substantially along the ridge strike with increasing distance from Iceland’s hotspot. A clearly
pronounced regularity of changes is observed in the rift zone’s morphology from the axial uplift (in the northern part of
the ridge) to the rift valleys (in the southern part of the ridge) through an intermediate or transitional type of morphology.
The results of numerical modeling showed that changes in the rift zone’s morphology along the Reykjanes Ridge strike are largely
caused by changes in the degree of mantle heating and depend on the intensity of magma supply. It is shown that under conditions
of ultraslow spreading, it is these parameters that control the presence or absence of crustal magma chambers, as well as
the thickness of the effectively-elastic layer of the axial lithosphere. The experimental modeling of topography-forming deformations
and structuring on the Reykjanes Ridge showed that under oblique extension, specific features of the formation of axial fractures
and the character of their segmentation mainly depend on the thickness of the axial lithosphere, its heating zone width, and
the kinematics of spreading. The experiments also showed that the tendency of fractures to develop obliquely to the extension
axis is caused by the action of the inclined zone of the location of the deformation, and shear deformations play a substantial
role in the lithosphere’s destruction as the inclination angle increases. 相似文献
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The off-axis topography of spreading ridges is a result of tectonic and magmatic processes occurring in the axial zone and operating off the ridge axis during further evolution of the crust. The results of physical and numerical simulations have shown that differences in topography roughness, rift valley depth, frequency and amplitude of normal faults, and geometric stability of the rift axis are determined by (a) the rate of extension and accretion of the new crust, (b) the thickness of the brittle lithospheric layer, and (c) the temperature of the underlying asthenosphere. Under conditions of the fast spreading, the stationary axial magma chamber in the crust predetermines the existence of the thinner and weakened lithosphere. As a result, the axis jumps for a short distance and the axis geometry remains almost rectilinear. The destruction of the thin axial lithosphere with a low mechanical strength results in formation of frequent and low-amplitude normal faultings. All these factors lead to the formation of the characteristic poorly dissected topography of fast-spreading ridges. Without a stationary axial magmatic chamber in the crust of slow-spreading ridges and with a thick and strong lithosphere, a deeply dissected axial and off-axis topography arises. The axis jumps for a significant distance within the rift valley, giving rise to geometric instability of the axis and development of transform and nontransform offsets. 相似文献
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E. P. Dubinin A. V. Kokhan D. E. Teterin A. L. Grokhol’sky E. S. Kurbatova N. M. Sushchevskaya 《Geotectonics》2016,50(1):35-53
Western, central, and eastern provinces are recognized in the Scotia Sea. They are distinguished by their bottom topography, geophysical characteristics, and crustal structure, which record their different origin and evolution. The western province is characterized by the oceanic crust that formed on the West Scotia Ridge, where active spreading may have ceased as a result of a collision between propagating rift and the structural barrier of the thick continental lithosphere of the Falkland Plateau. The central province is a series of blocks mainly composed of continental crust that subsided to various depths depending on the degree of extension in the course of rifting. These blocks are separated by local areas with oceanic crust formed due to the breakup of the continental crust and diffusive spreading. These areas are characterized by deep bottom and high values of Bouguer anomalies. The southern framework of the central province consists of subsided continental blocks and microcontinents divided by small spreading-type basins formed by lithospheric extension complicated by strike-slip faulting. The eastern province is composed of oceanic crust formed on the backarc spreading East Scotia Ridge. The results of density analysis, analog, and numerical simulations allowed us to explain some features of the structure and evolution of these provinces. The insight into tectonic structure of the provinces and their evolution allowed us to recognize several types of riftogenic basins differing in geodynamics, age, and geological and geophysical characteristics. 相似文献
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Geotectonics - The structure and evolution of the eastern part of the Southwest Indian Ridge are discussed. Based on geological-geophysical data and cartographic materials, analysis of spatial and... 相似文献
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