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A new numerical met...
A new numerical method to calculate inhomogeneous and time dependent large deformations of two-dimensional geodynamic flows with application to diapirism
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- Fuchs, Lukas (författare)
- Uppsala universitet,Mineralogi, petrologi och tektonik
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- Schmeling, Harro (författare)
- Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany
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(creator_code:org_t)
- 2013-05-09
- 2013
- Engelska.
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Ingår i: Geophysical Journal International. - : Oxford University Press (OUP). - 0956-540X .- 1365-246X. ; 194:2, s. 623-639
- Relaterad länk:
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https://academic.oup...
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visa fler...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- A key to understand many geodynamic processes is studying the associated large deformation fields. Finite deformation can be measured in the field by using geological strain markers giving the logarithmic strain f = log 10(R), where R is the ellipticity of the strain ellipse. It has been challenging to accurately quantify finite deformation of geodynamic models for inhomogeneous and time-dependent large deformation cases. We present a new formulation invoking a 2-D marker-in-cell approach. Mathematically, one can describe finite deformation by a coordinate transformation to a Lagrangian reference frame. For a known velocity field the deformation gradient tensor, F, can be calculated by integrating the differential equation DtFij = LikFkj, where L is the velocity gradient tensor and Dt the Lagrangian derivative. The tensor F contains all information about the minor and major semi-half axes and orientation of the strain ellipse and the rotation. To integrate the equation centrally in time and space along a particle's path, we use the numerical 2-D finite difference code FDCON in combination with a marker-in-cell approach. For a sufficiently high marker density we can accurately calculate F for any 2-D inhomogeneous and time-dependent creeping flow at any point for a deformation f up to 4. Comparison between the analytical and numerical solution for the finite deformation within a Poiseuille–Couette flow shows an error of less than 2 per cent for a deformation up to f = 1.7. Moreover, we determine the finite deformation and strain partitioning within Rayleigh–Taylor instabilities (RTIs) of different viscosity and layer thickness ratios. These models provide a finite strain complement to the RTI benchmark of van Keken et al. Large finite deformation of up to f = 4 accumulates in RTIs within the stem and near the compositional boundaries. Distinction between different stages of diapirism shows a strong correlation between a maximum occurring deformation of f = 1, 3 and 4, and the early, intermediate and late stages of diapirism, respectively. Furthermore, we find that the overall strain of a RTI is concentrated in the less viscous regions. Thus, spatial distributions and magnitudes of finite deformation may be used to identify stages and viscosity ratios of natural cases.
Ämnesord
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Multidisciplinär geovetenskap (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geosciences, Multidisciplinary (hsv//eng)
Nyckelord
- Numerical modelling
- Diapirism
- Finite Deformation
- Dynamics of lithosphere and mantle
- Diapir and diapirism
- convection currents
- mantle plumes
- Geovetenskap med inriktning mot mineralogi, petrologi och tektonik
- Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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