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| Titel |
Triclinic Transpression in brittle shear zones evaluated via combined numerical and analogue modeling: the case of The Torcal de Antequera Massif, SE Spain. |
| VerfasserIn |
Leticia Barcos, Manuel Díaz-Azpiroz, Claudio Faccenna, Juan Carlos Balanya, Inmaculada Expósito, Alejandro Giménez-Bonilla |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081869
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| Zusammenfassung |
| Numerical kinematic models have been widely used to understand the parameters
controlling the generation and evolution of ductile transpression zones. However,
these models are based on continuum mechanics and therefore, are not as useful to
analyse deformation partitioning and strain within brittle-ductile transpression zones.
The combination of numerical and analogue models will potentially provide an
effective approach for a better understanding of these processes and, to a broader
extent, of high strain zones in general. In the present work, we follow a combined
numerical and analogue approach to analyse a brittle dextral transpressive shear zone.
The Torcal de Antequera Massif (TAM) is part of a roughly E-W oriented shear
zone at the NE end of the Western Gibraltar Arc (Betic Cordillera). This shear
zone presents, according to their structural and kinematic features, two types of
domains i) Domain type 1 is located at both TAM margins, and is characterized by
strike-slip structures subparallel to the main TAM boundaries (E-W). ii) Domain type
2 corresponds to the TAM inner part, and it presents SE-vergent open folds and
reverse shear zones, as well as normal faults accommodating fold axis parallel
extension. Both domains have been studied separately applying a model of triclinic
transpression with inclined extrusion. The kinematic parameters obtained in this
study (φ, Ï
and Wk) allows us to constrain geometrical transpression parameters.
As such, the angle of oblique convergence (α, the horizontal angle between the
displacement vector and the strike of the shear zone) ranges between 10-17º (simple shear
dominated) for domain type 1 and between 31-35º (coaxial dominated) for domain type
2.
According to the results obtained from the numerical model and in order to validate its
possible utility in brittle shear zones we develop two analogue models with α values
representative of both domains defined in the TAM: 15º for type 1 and 30º for type 2. In the
treatment and analysis of generated structures, we applied digital particle image
velocimetry method (PIV), which allows us to calculate a velocity field of incremental
deformation.
Results show a sharp contrast between both experiments. For, α = 15º the main structures
formed were typical of the strike-slip regime, with two dextral strike-slip master faults
parallel to the backstop and Riedel and anti-Riedel minor faults. On the other hand, for α =
30º, the deformation was accommodated by a shear zone where the displacement was
partitioned between strike-slip movements along boundaries-parallel faults and shortening
mainly accommodated by structures formed at ca. 45º to the strike of the shear zone. These
results fairly resemble some of the main structures observed in the TAM and particularly, the
strain partitioning between the two main domain types, in relation to different α angles.
Also, our results suggest the application of numerical modelling in transpressive
zones related to upper crustal deformation provides the opportunity to constrain the
geometrical parameters to reproduce the main structural and kinematic features. |
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