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31.
V. P. Trubitsyn 《Doklady Earth Sciences》2010,434(1):1205-1207
32.
In the available numerical models, mantle plumes are represented by homogeneous ascending streams of thermal convection. Pulses are considered to be possible only in thermochemical plumes within the compositionally inhomogeneous mantle. We show that pulses can also occur under regular thermal convection in the homogeneous mantle. As the intensity grows, the flow in the tail of a thermal plume first begins pulsing and then the plume breaks up into a set of sequentially emerging thermals. For the present-day mantle, the pulsation periods for plumes in the lower mantle can range up to 10 Ma and about 1 Ma in the upper mantle. 相似文献
33.
According to an opinion widespread in the literature, high viscosity regions (HVRs) in the mantle always affect the structure of mantle flows, changing it in both the HVR itself and the entire mantle. Moreover, a simplified relation is often adopted according to which the flow velocity in the HVR decreases in inverse proportion to viscosity. Therefore, in order to treat a smoother value, some authors introduce a new variable equal to the product of the flow velocity and the viscosity value in a given place. On the basis of numerical modeling, this paper shows that HVRs of two types should be distinguished in the mantle. If an HVR is immobile, mantle flows actually do not penetrate it. If the viscosity increase is more than five orders, the HVR behaves as a solid and flow velocities within it almost vanish. However, if an HVR is free, it moves together with the mantle flow. Then, the general structure of flows changes weakly and flow velocities within the HVR become approximately equal to the average velocity of flows in the absence of the HVR. Horizontal layers and vertical columns differing in viscosity from the mantle behave as regions of the first type, whose flow velocities can differ by a few orders. However, even such large-scale regions as the continental lithosphere, whose viscosity is four to five orders higher than in the surrounding mantle, float together with continents at velocities comparable to mantle flows, i.e., behave as regions of the second type. 相似文献
34.
V. P. Trubitsyn A. A. Baranov A. N. Evseev A. P. Trubitsyn E. V. Kharybin 《Izvestiya Physics of the Solid Earth》2006,42(12):979-986
Numerical simulation in recent years has revealed that the cold lithosphere, whose viscosity is three to four orders of magnitude higher than that of the underlying mantle, behaves during mantle convection as a stagnant lid. On the basis of model calculations, this paper shows how convection changes over to this regime with increasing viscosity. Spatially fixed high viscosity inclusions and those moving with the convective flow have fundamentally different effects on the structure of convective flows. The model calculations indicate that anomalously low viscosity asthenospheric regions also lead to a specific regime of convection. With a decrease in the viscosity by more than three orders of magnitude, a further reduction in the viscosity of the region ceases to influence the structure of convection in the outer region. The boundary with this region behaves as a freely permeable boundary. In the low viscosity asthenospheric region itself, autonomous convection can arise under certain conditions. 相似文献
35.
V. P. Trubitsyn A. A. Baranov A. N. Eyseev A. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2006,42(7):537-545
Presently, the study of the mantle flow structure is mainly based on numerical modeling. The most important stage of the development of a computer program is its testing. For this purpose, results of various test models of convection flows with a given set of parameters are compared. The solution of the Stokes equation, involving the derivative of viscous stresses, is most difficult. Exact analytical solutions of the Stokes equation are obtained in this work for various cases of special loads. These solutions can be used as benchmarks for testing programs of numerical calculation of viscous flows in both geophysics and engineering. The advantage of this testing technique is the exceptional simplicity of the solution form, the admissibility of any spatial viscosity variations, and the fact that solutions can be compared not for a narrow set of the solution parameters but for any distributions of velocities, viscous stresses, and pressures at all points of the space. 相似文献
36.
Doklady Earth Sciences - In general, stresses and strains in the oceanic plates are studied on the basis of the theory of elastic bending of thin plates. Due to the fact that the thickness of the... 相似文献
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Doklady Earth Sciences - The observed heat flux from the Earth is created mainly by the heat released due to radioactive decay, secular cooling of the Earth, and solidification of the growing inner... 相似文献
38.
V. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2010,46(10):807-816
In the existing kinematic theory of the tectonics of lithospheric plates, the position and the parameters of plates are assigned a priori in the initial and boundary conditions. However, in the self-consistent dynamic theory, the properties of oceanic plates (as well as the structure of the mantle’s convection) should appear automatically as the solution of the differential equations of energy, mass, and momentum transfer for a viscous fluid. In this case, the viscosity of the mantle’s substance as a function of temperature, pressure, shear stress, and chemical composition must be taken from the data of laboratory measurements. In the present work, the results of the numerical solution of the equations of convection are presented in the problem formulation mentioned above on a simple model of heated viscous fluid with properties that correspond to the mantle’s substance. In this case, to reveal the main reason for the generation of plates and their influence on the convection, a number of simplifications are introduced; in particular, temperature variations in the viscosity in the mantle are disregarded. In spite of the undertaken simplifications, the models show how the rigid lithosphere can be split into separate plates immersed in the mantle, how in the course of evolution the sizes of plates and their number can change, and how in this case the ridges and subduction zones can be displaced. 相似文献
39.
V. P. Trubitsyn 《Izvestiya Physics of the Solid Earth》2010,46(11):922-930
Basalts of mid-ocean ridges are depleted in incompatible elements that have passed into the continental crust. Basalts of
hot spots (oceanic islands and igneous provinces) have a chemical composition close to the primary uniform mantle and are
even somewhat enriched in incompatible elements. At present, for explaining the reason for this difference, there are different
qualitative schemes of differentiation and mixing of substance in the mantle. In the present work, the results of numerical
modeling of the two-component thermochemical convection in the mantle are given. They quantitatively demonstrate with which
parameters in the mantle the layers of different chemical composition can remain unchanged. Models with different density
contrasts and with variable viscosity are examined. The times of the partial mixing of layers depending on the values of these
parameters are calculated. For retaining the stratified mantle for two Ga, the density contrast must be more than 2%. If the
layer D″ contains a substance of the primary composition, then, its upper boundary can be the place of origin of the plumes that
feed the hot spots of the Earth. The enrichment in the incompatible elements and the variety of the chemical composition of
hot spots can be explained by the mixing of the substance of the slowly eroded D″ layer and the oceanic crust accumulated in it. 相似文献
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