Cooling induced strain localization in carbonate mylonites within a large-scale shear zone (Glarus thrust, Switzerland)

Ebert, Andreas W.; Herwegh, Marco; Pfiffner, Othmar-Adrian

doi:10.1016/j.jsg.2007.03.007

Cited by 73 publications

(118 citation statements)

References 90 publications

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“…see also Ebert 2006, Ebert et al 2007b calcite dissolution and vein formation are simultaneously active, as is indicated by the formation of calcite veins that were subsequently deformed. Hence, deformation is of a composite character and involves dislocation creep, as well as fracturing and mass transfer processes.…”

Section: Deformation Fabricsmentioning

confidence: 96%

“…in the younger Lt mylonites, different potential deformation processes were inferred from microstructural investigations (Ebert 2006, Ebert et al 2007b): (a) dislocation creep assisted grain boundary sliding (superplasticity, schmid et al 1977(superplasticity, schmid et al , Pfiffner 1982; (b) granular flow, whereby the rotation of grains was accommodated at grain boundaries by a combination of dissolution-precipitation processes and grain boundary sliding and (c) cataclastic deformation. in the last case, an ultra-fine grained carbonaceous gouge (ultracataclasite) would have developed, with syn-to post-kinematic fluid circulation resulting in slight coarsening of the grains and their cementation after cataclasis.…”

Section: Younger Low-temperature (Lt) Mylonitesmentioning

confidence: 99%

“…Both superplasticity and granular flow involve negligible or no contributions of intracrystalline plasticity towards the deformation of the aggregate. in case of the Glarus thrust, the striking evidence for synkinematic fluid flow and the associated components of mass transfer recently motivated Ebert et al (2007b) to favor the term 'granular flow' over the previously suggested term 'superplastic flow ' (schmid et al 1977;Pfiffner 1982). On the other hand, s. schmid proposed that one could also argue that mass transfer only occurred during intermittent cycles associated with brittle fracturing, induced by high pore pressure events.…”

Section: Younger Low-temperature (Lt) Mylonitesmentioning

confidence: 99%

“…recently, new developments in quantitative microfabric analysis (e.g. electron backscatter diffraction, digital image processing and analysis) provoked a series of new microstructural and geochemical investigations (Ebert 2006, Ebert et al 2007b, Hürzeler and abart 2008, which tried to link small-scale deformation and geochemical processes with the large-scale evolution of the Glarus thrust.…”

Section: Introductionmentioning

confidence: 99%

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The Glarus thrust: excursion guide and report of a field trip of the Swiss Tectonic Studies Group (Swiss Geological Society, 14.–16. 09. 2006)

et al. 2008

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the Glarus thrust 323 aBstract this excursion guide results form a field trip to the Glarus nappe complex organized by the swiss tectonic studies Group in 2006. the aim of the excursion was to discuss old and recent concepts related to the evolution of the Glarus thrust. the major aspects were (i) the interplay between deformation, fluid flow and geochemical alteration, (ii) episodic versus continuous deformation and fluid flow, and (iii) the link between large-scale structures, microstructures, and geochemical aspects. Despite 150 years of research in the Glarus nappe complex and the new results discussed during the excursion, there exist controversies that still are unsolved.

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Section: Deformation Fabricsmentioning

confidence: 96%

Section: Younger Low-temperature (Lt) Mylonitesmentioning

confidence: 99%

Section: Younger Low-temperature (Lt) Mylonitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Glarus thrust: excursion guide and report of a field trip of the Swiss Tectonic Studies Group (Swiss Geological Society, 14.–16. 09. 2006)

et al. 2008

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“…We conclude that the deformation mechanisms operating in a localized process zone are close to the field boundary. In natural carbonate-rich shear zones, localization may be further enhanced by second phase particles and stress or temperature-induced grain size reduction (Ebert et al, 2007a;Ebert et al, 2007b;Herwegh et al, 2008).…”

Section: Aggregate Strengthmentioning

confidence: 99%

Strain localization during high temperature creep of marble: The effect of inclusions

et al. 2014

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The deformation of rocks in the Earth's middle and lower crust is often localized in ductile shear zones. To better understand the initiation and propagation of high-temperature shear zones induced by the presence of structural and material heterogeneities, we performed deformation experiments in the dislocation creep regime on Carrara marble samples containing weak (limestone) or strong (novaculite) second phase inclusions. The samples were mostly deformed in torsion at a bulk shear strain rate of ≈ 1.9x10 -4 s -1 to bulk shear strains γ between 0.02 and 2.9 using a Paterson-type gas deformation apparatus at 900°C temperature and 400 MPa confining pressure. At low strain, twisted specimens with weak inclusions show minor strain hardening that is replaced by strain weakening at γ > 0.1 -0.2.Peak shear stress at the imposed conditions is about 20 MPa, which is ≈8% lower than the strength of intact samples. Strain progressively localized within the matrix with increasing bulk strain, but decayed rapidly with increasing distance from the inclusion tip.Microstructural analysis shows twinning and recrystallization within this process zone, with a strong crystallographic preferred orientation, dominated by {r} and (c) slip in .Recrystallization-induced weakening starts at local shear strain of about 1 in the process zone, corresponding to a bulk shear strain of about 0.1. In contrast, torsion of a sample containing strong inclusions deformed at similar stress as inclusion-free samples but do not show localization. The experiments demonstrate that the presence of weak heterogeneities initiates localized creep at local stress concentrations around the inclusion tips. Recrystallizationinduced grain size reduction may only locally promote grain boundary diffusion creep. Accordingly, the bulk strength of the twisted aggregate is close to or slightly below the lower (isostress) strength bound, determined from the flow strength and volume fraction of matrix and inclusions.

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Modeling episodic fluid‐release events in the ductile carbonates of the Glarus thrust

Poulet

Veveakis

Herwegh

et al. 2014

Geophysical Research Letters

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The exposed Glarus thrust displays midcrustal deformation with tens of kilometers of displacement on an ultrathin layer, the principal slip zone (PSZ). Geological observations indicate that this structure resulted from repeated stick-slip events in the presence of highly overpressured fluids. Here we show that the major characteristics of the Glarus thrust movement (localization, periodicity, and evidence of pressurized fluids) can be reconciled by the coupling of two processes, namely, shear heating and fluid release by carbonate decomposition. During this coupling, slow ductile creep deformation raises the temperature through shear heating and ultimately activates the chemical decomposition of carbonates. The subsequent release of highly overpressurized fluids forms and lubricates the PSZ, allowing a ductile fault to move tens of kilometers on millimeter-thick bands in episodic stick-slip events. This model identifies carbonate decomposition as a key process for motion on the Glarus thrust and explains the source of overpressured fluids accessing the PSZ.

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Cooling induced strain localization in carbonate mylonites within a large-scale shear zone (Glarus thrust, Switzerland)

Cited by 73 publications

References 90 publications

The Glarus thrust: excursion guide and report of a field trip of the Swiss Tectonic Studies Group (Swiss Geological Society, 14.–16. 09. 2006)

The Glarus thrust: excursion guide and report of a field trip of the Swiss Tectonic Studies Group (Swiss Geological Society, 14.–16. 09. 2006)

Strain localization during high temperature creep of marble: The effect of inclusions

Modeling episodic fluid‐release events in the ductile carbonates of the Glarus thrust

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