We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Weakening Processes and Strain Localization in Viscously Deforming Rocks: Numerical Modeling based on Laboratory Torsion Experiments.
- Authors
Döhmann, Maximilian; Brune, Sascha; Nardini, Livia; Rybacki, Erik; Dresen, Georg
- Abstract
Localization processes in the viscous lower crust lead to the formation of deformation zones over a broad range of scales. Weakening mechanisms on the grain scale cause strength reduction of rocks during localization. To gain insight into the processes involved, we conduct centimeter-scale numerical models with the finite element software SLIM3D. Our 2D models are benchmarked to high-temperature and high-pressure torsion experiments on Carrara marble samples containing a single weak Solnhofen limestone inclusion (Nardini et al., 2018). Bulk stress-strain evolution and final strain distribution are successfully reproduced by the numerical models. In order to mimic rheological weakening, a simple, strain dependent softening law is applied that alters the pre-exponential factor of the flow law. By varying softening parameter values within this modeling framework, the impact of rheological weakening on localization and shear zone formation is quantified.We find that strain localization inside the host matrix is initiated by local stress concentrations at the inclusion tips. Rheological weakening is a precondition for shear zone formation within the matrix. At the tip of the propagating shear zone, weakening occurs within a process zone that evolves in four phases (P1) pre-weakening, (P2) onset and acceleration of weakening, (P3) deceleration of weakening and (P4) steady-state. The degree of softening controls the shear zone width. With the introduction of a second softening step at elevated local strain, a high strain layer develops inside the already localized shear zone, analogue to the formation of ultramylonite bands in mylonites.ReferenceNardini, L., Rybacki, E., Döhmann, M. J., Morales, L. F., Brune, S., & Dresen, G. (2018). High-temperature shear zone formation in Carrara marble: The effect of loading conditions. Tectonophysics, 749, 120-139.
- Subjects
WEAK localization (Quantum mechanics); SHEAR zones; TORSION; STRESS concentration; ROCK deformation; ROCKS; GEODYNAMICS
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article