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Computer modeling of granite gneiss diapirism in the Earth’s crust: Controlling factors,duration, and temperature regime 总被引：1，自引：0，他引：1
This paper is devoted to the modeling the granite gneiss formation by means of diapiric upwelling. The natural examples of
granitic diapirism in the Precambrian granite-greenstone belts and complexes of metamorphic cores are described. A new approach
is proposed to describe the partial melting and development of gravity instability in the crustal granitic layer, which experienced
heat impact and melting during intrusion of basaltic melt. Rheology of partially melted material and surrounding medium is
regarded to be temperature-dependent, following either plasticity or creep (non-Newtonian viscosity) law. Modeling results
show that crustal rheology plays a significant role in the character of diapirism (shape of upwelling bodies, duration of
the process, and width of thermal aureole). The rates of upwelling within the crust behaving as elastoplastic body are orders
of magnitude higher (meters to tens meters per year) than those obtained for creep (viscous) liquid model (0.8 cm/yr). Modeling
results revealed that the limiting depth of upwelling of partially crystallized melt, with allowance for temperature dependence
of creep, corresponds to the isotherm of 400°C. 相似文献
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V. V. Reverdatto A. V. Babichev I. I. Likhanov O. P. Polyansky 《Doklady Earth Sciences》2018,480(2):750-752
The rate of mineral transformations in rocks near magmatic intrusions may be estimated using mathematical modeling for study of the duration of metamorphism and geological and mineralogical data. At the contacts of the Anakit trappean massif on the Nizhnyaya Tunguska River, where the temperature reached 900°C, the rate of growth of a wollastonite rim at the boundary between the limestone and the siliceous nodule was ～3 × 10–10 cm/s. The zone of “spotted” hornfels with a width of 300?400 m was formed during metamorphism of chlorite–sericite–epidote–albite–quartz schist near the Kharlov gabbro massif in the foothills of the Altai Mountains. The movement rate of the metamorphic front during the formation of rock may be estimated as ～2 × 10–8 cm/s. It is suggested that the rate of metamorphism is controlled by the temperature and rock composition. As a whole, the rates of metamorphism of rocks near magmatic intrusive bodies exceed the rates of regional metamorphism. Upon accumulation of the actual data, this may be applied for diagnostics of the types of metamorphism. 相似文献
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O.P. Polyansky A.V. Prokopiev O.V. Koroleva M.D. Tomshin V.V. Reverdatto A.V. Babichev V.G. Sverdlova D.A. Vasiliev 《Russian Geology and Geophysics》2018,59(10):1217-1236
Possible mechanisms of rifting and the thermal regime of the lithosphere beneath the rift zone of the Vilyui sedimentary basin are considered based on the available isotopic ages of dike swarms, rates of sedimentation, and results of numerical modeling. Temporal correlations between the intrusion of mafic magma and a sharp increase in the rate of subsidence and sedimentation in the rift basin prove the contribution of both plate-tectonic and magmatic factors to the formation of the Vilyui rift. The results show a relationship between the rapid extension of the lithosphere and the formation of mafic dike swarms in the Yakutsk-Vilyui Large Igneous Province of the Siberian Platform at the Frasnian-Famennian boundary, with a peak at ~ 374.1 Ma, and at the end of the Late Devonian, with a peak at ~ 363.4 Ma. There were two pulses of dike formation during rapid subsidence of the basin basement in the period 380-360 Ma, with a sedimentation rate of 100-130 m/Myr, at a background rate of 10-20 m/Myr. Analysis of numerical thermomechanical models revealed that the best-fit model is that combining the mechanisms of intraplate extension (passive rifting) and the ascent of a mantle magmatic diapir (active rifting). A conclusion about the nature of the heat source of trap magmatism has been drawn: The plume-driven regime of the lithosphere can better explain the dynamics of extension during rifting than the decompression melting mechanism. 相似文献
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O.P. Polyansky A.V. Prokop'ev A.V. Babichev S.N. Korobeynikov V.V. Reverdatto 《Russian Geology and Geophysics》2013,54(2):121-137
Results of modeling of the formation of the Vilyui sedimentary basin are presented. We combine backstripping reconstructions of sedimentation and thermal regime during the subsidence with a numerical simulation based on the deformable solid mechanics. Lithological data and stratigraphic sections were used to “strip” the sedimentary beds successively and calculate the depth of the stratigraphic units during the sedimentation. It is the first time that the evolution of sedimentation which is nonuniform over the basin area has been analyzed for the Vilyui basin. The rift origin of the basin is proven. We estimate the spatial distribution of the parameters of crustal and mantle-lithosphere extension as well as expansion due to dike intrusion. According to the reconstructions, the type of subsidence curves for the sedimentary rocks of the basin depends on the tectonic regime of sedimentation in individual basins. The backstripping analysis revealed two stages of extension (sediments 4–5 km thick) and a foreland stage (sediments > 2 km thick). With the two-layered lithosphere model, we conclude that the subcrustal layer underwent predominant extension (by a factor of 1.2–2.0 vs. 1.1–1.4 in the crust). The goal of numerical experiments is to demonstrate that deep troughs can form in the continental crust under its finite extension. Unlike the oceanic rifting models, this modeling shows no complete destruction or rupture of the continental crust during the extension. The 2D numerical simulation shows the possibility of considerable basement subsidence near the central axis and explains why mafic dikes are concentrated on the basin periphery. 相似文献
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This paper reports the results of the numerical modeling of gravitationally instable processes in the lithospheric mantle
of ancient cratons. The gravitational instability is considered as a result of melting at the lithosphere base owing to its
local heating by anomalous mantle. Modeling was based on a finite element method in 2D formulation and took into account the
geological structure and thermomechanical parameters of the lithosphere of the Siberian platform. Numerical results revealed
the main tendencies in the mantle diapirisim of the mafic and ultramafic magma ascending through the “cold” high-viscosity
lithosphere. It was shown that the shape of diapiric magmatic bodies is controlled by realistic visco-elastic-plastic rheology
of lithosphere. The ascent of diapir in lithosphere was modeled for diverse regimes differing in duration, temperature field,
and upwelling depth. It was concluded that the ascent of melt through lithosphere to the crust-mantle boundary is mainly controlled
by rheology, and conditions of oscillatory diapirism with recurrent magma replenishments were modeled. Modeling results may
shed light on some features related to the trap magmatism of the Siberian igneous province. The duration and rate of magma
upwelling as well as the parameters of periodical magma upwelling were estimated and attempt was made to explain the high-velocity
seismic anomalies that were recorded in the subcrustal regions of the Siberian platform. 相似文献
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A two-dimensional modelling study of sedimentation, fluid flow, and heat flow in the Baikal rift basin undergoing flank uplift and basin subsidence has been performed in order to understand the impact of these processes on the surface heat flow signal. Heat flow anomalies of different scales and magnitudes have been observed at the sediment surface of the lake Baikal basin, and the presence of a hydrothermal vent suggests that fluids play an important role in the regional distribution of heat flow. The BASIN-code applied for this study allows to simulate topographically and compaction-driven hydrodynamical fluid flow and coupled heat transfer.The flank uplift history provides the basis for a regional groundwater circulation towards the central basin area, with predicted Darcy velocities at present-day situation in the basement varying between 1 and 100 cm/year. Within the basin, the presence of aquifers and the pinch-out layering has a major control on the flow field, and compaction-driven flow velocities are strongly altered when combined with topography-driven flow. When velocities in the basement are larger than several centimeters per year, the regional fluid circulation is an effective mechanism of heat redistribution. Heat is brought from the flanks towards the basin area, with largest heat transported at a depth of 1–2 km at both sides. During the flank uplift, heat advection increases, with secondary variation related to the deposition of sedimentary layers. The heat flow is increased over the basin and reduced in the flanks, with a total heat output balance always positive. The extra heat output over the modelled transection is 2–10% of the initial heat output. The maximum computed heat fluxes are smaller than measured in the heat flow anomalies of the lake Baikal basin. Nevertheless, the model suggests that flow in the sedimentary basin combined with a topographically driven heat advection in the surrounding basement is a sufficient mechanism to account for the increased heat flow over the basin and the main features of the heat flow distribution. 相似文献