Rheology of eclogites: Comparison of high pressure-temperature deformation experiments and natural examples

2017-2020: Austrian Science Fund (FWF) P 29539-N29

Principal Investigators:

Anna Rogowitz (University of Vienna)
­­Bernhard Grasemann (University of Vienna)


Joerg Renner (Ruhr-University Bochum, Germany)


Katrin Kraus (University of Vienna)

The rheological behaviour of rocks is directly reflected by the formation of tectonic structures like folds, boudins or shear zones and is one of the main controlling factors of deformation at the plate boundaries and interiors.
Besides temperature the rheological behaviour of a rock is largely controlled by the relative amount, distribution and strength of its minerals.

In this project we will study the rheological behaviour and microstructural evolution of eclogites composed of omphacite and garnet in varying fractions and in different strain, strain rate, pressure and temperature conditions.

Owing the formation and presence of potentially large amounts of eclogite their deformation behaviour is of great importance for the rheology of the lithosphere in continental collision and subduction zones.

The investigations will be based on triaxial deformation tests at high temperature and high pressure conditions characteristic for in-situ conditions at plate boundaries.
The samples will be synthesized in a piston cylinder apparatus to control the relative proportions of omphacite and garnet.
Rheological laws for eclogites of different compositions in different regimes will be determined suitable for large scale modelling.
Additionally detailed microfabric analysis of experimentally and naturally deformed eclogites from the Type-locality (Koralpe and Saualpe, Austria) will be performed using optical microscopy and high resolution techniques (scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy).
By comparing experimental microstructures and associated deformation mechanisms to natural ones we will get information on deformation conditions and mechanisms of the natural deformed eclogites.

The results of this study will provide important constraints for our understanding of the rheology and deformation behaviour of eclogites, and thus improve the understanding of processes at greater depths in subduction and collision zones. Additionally crucial insights for the behaviour of two-phase rocks will be gained.