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| Titel |
The role of mechanical heterogeneities during continental breakup: a 3D lithospheric-scale modelling approach |
| VerfasserIn |
Guillaume Duclaux, Ritske S. Huismans, Dave May |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104217
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| Publikation (Nr.) |
 EGU/EGU2015-3640.pdf |
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| Zusammenfassung |
| How and why do continents break? More than two decades of analogue and 2D plane-strain
numerical experiments have shown that despite the origin of the forces driving extension, the
geometry of continental rifts falls into three categories - or modes: narrow rift, wide rift, or
core complex. The mode of extension itself is strongly influenced by the rheology (and
rheological behaviour) of the modelled layered system. In every model, an initial thermal or
mechanical heterogeneity, such as a weak seed or a notch, is imposed to help localise the
deformation and avoid uniform stretching of the lithosphere by pure shear. While it is
widely accepted that structural inheritance is a key parameter for controlling rift
localisation - as implied by the Wilson Cycle - modelling the effect of lithospheric
heterogeneities on the long-term tectonic evolution of an extending plate in full 3D remains
challenging.
Recent progress in finite-element methods applied to computational tectonics along with the
improved accessibility to high performance computers, now enable to switch from plane
strain thermo-mechanical experiments to full 3D high-resolution experiments. Here we
investigate the role of mechanical heterogeneities on rift opening, linkage and propagation
during extension of a layered lithospheric systems with pTatin3d, a geodynamics modeling
package utilising the material-point-method for tracking material composition, combined
with a multigrid finite-element method to solve heterogeneous, incompressible visco-plastic
Stokes problems.
The initial model setup consists in a box of 1200 km horizontally by 250 km deep. It
includes a 35 km layer of continental crust, underlaid by 85 km of sub-continental
lithospheric mantle, and an asthenospheric mantle. Crust and mantle have visco-plastic
rheologies with a pressure dependent yielding, which includes strain weakening,
and a temperature, stress, strain-rate-dependent viscosity based on wet quartzite
rheology for the crust, and wet olivine for the mantle. A constant extension rate
is imposed on two opposite walls in the horizontal direction; the model’ surface
evolves freely; an isostatic boundary condition is imposed on the bottom wall. We
explore a range of weak notches geometries, as well as the presence of random noise
across a central region of the model. We compare the evolution of the geometry
of the surface rift segments, their linkage and faults propagation during ongoing
extension.
These models allow us to assess the importance of mechanical heterogeneities for controlling
passive margin geometries, and to precise the underlying physics governing continental
breakup. |
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