 |
| Titel |
Crust rheology, slab detachment and topography |
| VerfasserIn |
T. Duretz, T. V. Gerya |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060450
|
|
|
|
|
|
| Zusammenfassung |
| The collision between continents following the closure of an ocean can lead to the subduction
of continental crust. The introduction of buoyant crust within subduction zones triggers the
development of extensional stresses in slabs which eventually result in their detachment. The
dynamic consequences of slab detachment affects the development of topography, the
exhumation of high-pressure rocks and the geodynamic evolution of collision zones. We
employ two-dimensional thermo-mechanical modelling in order to study the importance of
crustal rheology on the evolution of spontaneous subduction-collision systems and the
occurrence of slab detachment. The modelling results indicate that varying the rheological
structure of the crust can results in a broad range of collisional evolutions involving slab
detachment, delamination (associated to slab rollback), or the combination of both
mechanisms. By enhancing mechanical coupling at the Moho, a strong crust leads to
the deep subduction of the crust (180 km). These collisions are subjected to slab
detachment and subsequent coherent exhumation of the crust accommodated by
eduction (inversion of subduction sense) and thrusting. In these conditions, slab
detachment promotes the development of a high (> 4.5 km) and narrow (< 200 km)
topographic plateau located in the vicinity of the suture. A contrasting style of collision is
obtained by employing a weak crustal rheology. The weak mechanical coupling at the
Moho promotes the widespread delamination of the lithosphere, preventing slab
detachment to occur. Further shortening leads to buckling and thickening of the crust
resulting in the development of topographic bulging on the lower plate. Collisions
involving rheologically layered crust are characterised by a decoupling level at
mid-crustal depths. These initial condition favours the delamination of the upper
crust as well as the deep subduction of the lower crust. These collisions are thus
successively affected by delamination and slab detachment and both processes
contribute to the exhumation of the subducted crust. A wide (> 200 km) topographic
plateau develops as the results of the buoyant extrusion of the upper crust onto
the foreland, this mechanism is further amplified by slab detachment. Our results
suggest that the occurrence of both delamination (Apennines) and slab detachment
(Himalayas) in orogens may highlight significant differences in their initial rheological
structure. |
|
|
|
|
|
|