EGU25-5144, updated on 30 Apr 2025
https://doi.org/10.5194/egusphere-egu25-5144
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
 On the role of transformation-induced physical changes on eclogite propagation: insights from thermo-mechanical numerical models.
Anaïs Cochet1, Philippe Yamato1, Marie Baïsset1, Loïc Labrousse2, and Thibault Duretz3
Anaïs Cochet et al.
  • 1Univ Rennes, CNRS, Géosciences Rennes - UMR 6118, F-35000 Rennes, France
  • 2Sorbonne Université, CNRS-INSU, Institut Des Sciences de La Terre Paris, ISTeP, UMR7193, Paris, France
  • 3Institüt für Geowissenschaften, Goethe Universität, 60438 Frankfurt am Main, Germany

In convergence zones, metamorphic transformations that affect the subducting lithosphere as due to changes in pressure and temperature significantly influence the mechanical behavior of rocks. For instance, eclogitization of lower crustal rocks, characterized by a notable densification has been associated with strain localization and seismic activity in several localities around the world. However, the mechanisms governing the propagation of this transformation once initiated remain insufficiently understood. In that prospect, this study investigates the process of eclogitization through thermo-mechanical numerical modeling, focusing on the deformation of an inclusion within a reactive matrix of different viscosity. This matrix-inclusion system is deformed under pure shear boundary conditions, and the physical properties of the initial materials evolve toward those of the transformation product in areas of the model where the pressure of the transformation is reached.

A parametric analysis is conducted to assess the influence of a heterogeneous pressure field generated by mechanical heterogeneities on the initiation and propagation of the transformation. Our results show that pressure overstepping and initial viscosity of the material are key factors to trigger the transformation. Other parameters such as (1) density variations during the transformation, (2) the initial viscosity contrast between the matrix and the inclusion, and (3) the shape/orientation of the inclusion instead enhance or inhibit the propagation of the transformation. Additionally, our results show that the direction of the eclogite propagation is systematically perpendicular to the shortening direction. These results show striking similarities with field observations and structural analyses of finger-shaped eclogite fronts on the island of Holsnøy (Norway).

How to cite: Cochet, A., Yamato, P., Baïsset, M., Labrousse, L., and Duretz, T.:  On the role of transformation-induced physical changes on eclogite propagation: insights from thermo-mechanical numerical models., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5144, https://doi.org/10.5194/egusphere-egu25-5144, 2025.

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