Shear localisation in anisotropic, non-linear viscous materials that develop a CPO

A numerical study

Tamara de Riese* (Corresponding Author), Lynn Evans, Enrique Gomez-Rivas, Albert Griera, Ricardo A. Lebensohn, Maria Gema Llorens, Hao Ran, Till Sachau, Ilka Weikusat, Paul D. Bons

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Localisation of ductile deformation in rocks is commonly found at all scales from crustal shear zones down to grain scale shear bands. Of the various mechanisms for localisation, mechanical anisotropy has received relatively little attention, especially in numerical modelling. Mechanical anisotropy can be due to dislocation creep of minerals (e.g. ice or mica) and/or layering in rocks (e.g. bedding, cleavage). We simulated simple-shear deformation of a locally anisotropic, single-phase power-law rheology material up to shear strain of five. Localisation of shear rate in narrow shear bands occurs, depending on the magnitude of anisotropy and the stress exponent. At high anisotropy values, strain-rate frequency distributions become approximately log-normal with heavy, exponential tails. Localisation due to anisotropy is scale-independent and thus provides a single mechanism for a self-organised hierarchy of shear bands and zones from mm-to km-scales. The numerical simulations are compared with the natural example of the Northern Shear Belt at Cap de Creus, NE Spain.

Original languageEnglish
Pages (from-to)81-90
Number of pages10
JournalJournal of Structural Geology
Volume124
Early online date3 Apr 2019
DOIs
Publication statusPublished - Jul 2019

Fingerprint

anisotropy
shear band
shear zone
dislocation creep
ductile deformation
shear strain
rheology
strain rate
mica
rock
cleavage
power law
material
ice
mineral
modeling
simulation

Keywords

  • Anisotropy
  • Self-organisation
  • Shear zones
  • Strain localisation
  • Strain-rate distribution

ASJC Scopus subject areas

  • Geology

Cite this

Shear localisation in anisotropic, non-linear viscous materials that develop a CPO : A numerical study. / de Riese, Tamara (Corresponding Author); Evans, Lynn; Gomez-Rivas, Enrique; Griera, Albert; Lebensohn, Ricardo A.; Llorens, Maria Gema; Ran, Hao; Sachau, Till; Weikusat, Ilka; Bons, Paul D.

In: Journal of Structural Geology, Vol. 124, 07.2019, p. 81-90.

Research output: Contribution to journalArticle

de Riese, T, Evans, L, Gomez-Rivas, E, Griera, A, Lebensohn, RA, Llorens, MG, Ran, H, Sachau, T, Weikusat, I & Bons, PD 2019, 'Shear localisation in anisotropic, non-linear viscous materials that develop a CPO: A numerical study', Journal of Structural Geology, vol. 124, pp. 81-90. https://doi.org/10.1016/j.jsg.2019.03.006
de Riese, Tamara ; Evans, Lynn ; Gomez-Rivas, Enrique ; Griera, Albert ; Lebensohn, Ricardo A. ; Llorens, Maria Gema ; Ran, Hao ; Sachau, Till ; Weikusat, Ilka ; Bons, Paul D. / Shear localisation in anisotropic, non-linear viscous materials that develop a CPO : A numerical study. In: Journal of Structural Geology. 2019 ; Vol. 124. pp. 81-90.
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AU - Llorens, Maria Gema

AU - Ran, Hao

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AU - Bons, Paul D.

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N2 - Localisation of ductile deformation in rocks is commonly found at all scales from crustal shear zones down to grain scale shear bands. Of the various mechanisms for localisation, mechanical anisotropy has received relatively little attention, especially in numerical modelling. Mechanical anisotropy can be due to dislocation creep of minerals (e.g. ice or mica) and/or layering in rocks (e.g. bedding, cleavage). We simulated simple-shear deformation of a locally anisotropic, single-phase power-law rheology material up to shear strain of five. Localisation of shear rate in narrow shear bands occurs, depending on the magnitude of anisotropy and the stress exponent. At high anisotropy values, strain-rate frequency distributions become approximately log-normal with heavy, exponential tails. Localisation due to anisotropy is scale-independent and thus provides a single mechanism for a self-organised hierarchy of shear bands and zones from mm-to km-scales. The numerical simulations are compared with the natural example of the Northern Shear Belt at Cap de Creus, NE Spain.

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