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| Titel |
Shear localization in foliated media: numerical experiments with application to the Bethique (Spain). |
| VerfasserIn |
Laetitia Le Pourhiet, Philippe Agard, Benjamin Huet, Loïc Labrousse, Laurent Jolivet |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036232
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| Zusammenfassung |
| Field data have been gathered in the Bethique (Spain) and studied systematically
at map, outcrop and thin section scale. The field area has been chosen for being
lithologically homogeneous at map scale and the results indicates a systematic
angle of 22° between the shear bands and the schistosity. Trying to understand the
systematics in this observation, we have design a numerical parametric study that consists
of hundreds of numerical runs in which we consider a initial 4 by 1 rectangular
section filled by layers of two visco-elasto-plastic material of different viscosity. We
neglect the effect of temperature and gravity. Instead of modeling the whole crust,
we account for a confining pressure. The sections were sheared up to γ = 1.5 in
bulk.
We varied the angle between the pre-existing schistosity (S) and the shearing direction
(C) and found that depending on the sense of shearing versus the dipping direction of the
initial layering the model turns into boudinage or folding at angles less than 45°. However, as
the angle between the schistosity and the direction of shear increases towards 45° , the
obtained structure tends to loss their co-axiality. When the dip was forming an angle of more
than 45°, the initial foliation rotates passively until reaching the critical angle of
45°.
In all those cases, we computed the evolution of stress versus strain in the bulk, the strong
and the weak layers, as well as detailed map of the finite strain and neoformed foliation. We
find that the folding cases always require more work than the boudinage ones. The shear
banding instabilities (localization) tends to occurs with a constant angle of 20-25° to the
foliation accordingly to observations. |
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