Dislocation creep of calcite

Renner, Jörg; Evans, Brian; Siddiqi, Gunter

doi:10.1029/2001jb001680

Cited by 91 publications

(131 citation statements)

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“…2 and 8a). We limit our analysis to flow laws for fine-grained carbonates (schmid et al 1977;Walker et al 1990;renner et al 2002;Herwegh et al 2003) (table 3), as these are most applicable to the microstructures observed in the Morcles nappe. Note that the parameters in these flow laws were obtained from experiments run to relatively low strains in triaxial compression: we will address the role of strain softening, as observed by barnhoorn et al (2004) during high-strain torsion experiments on coarse-grained carrara marble, in the next section.…”

Section: Are Microstructures Indicative Of Deformation Conditions?mentioning

confidence: 99%

Strain localization in the Morcles nappe (Helvetic Alps, Switzerland)

Austin

Evans

Herwegh³

et al. 2008

Swiss J. Geosci.

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Deformation in orogenic belts is frequently accommodated in calcite-rich lithologies, owing to their relatively low strength, particularly compared to quartz-rich rocks. Here, we investigate the coupling between calcite grain size, the presence and mineralogy of second phases, and crystallographic preferred orientation (cPO) in a transect through deformed limestones, perpendicular to the dominant foliation in the inverted limb of the Morcles nappe of the swiss Helvetic Alps. calcite grain size becomes progressively finer as the thrust contact is approached, and there is a concomitant increase in cPO intensity, with the strongest cPO's in the finest-grained, quartz-rich limestones, nearest the thrust contact. to understand the distribution of strain and the extent of strain localization, we compared the paleowattmeter and calcite flow laws from laboratory studies to previously published observations of microstructure at a range of locations, with varying peak metamorphic temperatures, along the Morcles nappe. the strain-rates predicted by extrapolation of these laboratory relationships agree well with the geologic constraints. We then applied the same approach to the samples from the present study. the results indicate that strain became progressively localized towards the thrust contact of the Morcles nappe, leading to an increase in strain rate of >1 order of magnitude in a zone <0.50 m thick. For localization to occur system and/or material softening is necessary. If dislocation activity is positively correlated with cPO, then softening cannot have occurred by a complete transition to diffusion creep in the finest grained samples. rather, softening may have resulted from the formation of cPO, possibly coupled with effects related to the distribution of second phases and the overall geometry of the shear zone. strain localization in the Morcles nappe (Helvetic Alps, switzerland)

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Section: Are Microstructures Indicative Of Deformation Conditions?mentioning

confidence: 99%

Strain localization in the Morcles nappe (Helvetic Alps, Switzerland)

Austin

Evans

Herwegh³

et al. 2008

Swiss J. Geosci.

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“…[6] A number of studies have already documented the mechanical behavior of Carrara marble along regular triaxial path [Rutter, 1974;Fredrich et al, 1989;Renner et al, 2002;Schubnel et al, 2005]. These studies showed that below 50 MPa confinement, deformation is brittle.…”

Section: Experimental Set-up and Proceduresmentioning

confidence: 99%

“…A number of these studies have documented the mechanical behavior of Carrara marble [Rutter, 1974;Fredrich et al, 1989;Renner et al, 2002;Schubnel et al, 2005]. In the cataclastic flow regime, it was demonstrated that deformation is dominated by dislocation creep [Renner et al, 2002], twinning and cracking [Fredrich et al, 1989]. Schubnel et al [2005] showed that the interactions between plastic deformation and brittle processes induced the pore space to either dilate (in creep) or compact (in pure relaxation), without any strain localization taking place.…”

Section: Introductionmentioning

confidence: 99%

Transient creep, aseismic damage and slow failure in Carrara marble deformed across the brittle‐ductile transition

Schubnel

Walker²,

Thompson

et al. 2006

Geophysical Research Letters

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[1] Two triaxial compression experiments were performed on Carrara marble at high confining pressure, in creep conditions across the brittle-ductile transition. During cataclastic deformation, elastic wave velocity decrease demonstrated damage accumulation (microcracks). Keeping differential stress constant and reducing normal stress induced transient creep events (i.e., fast accelerations in strain) due to the sudden increase of microcrack growth. Tertiary creep and brittle failure followed as damage came close to criticality. Coalescence and rupture propagation were slow (60 -200 seconds with $150 MPa stress drops and millimetric slips) and radiated little energy in the e x p e r i m e n t a l f r e q u e n c y r a n g e ( 0 . 1 -1 M H z ). Microstructural analysis pointed out strong interactions between intra-crystalline plastic deformation (twinning and dislocation glide) and brittle deformation (microcracking) at the macroscopic level. Our observations highlight the dependence of acoustic efficiency on the material's rheology, at least in the ultrasonic frequency range, and the role played by pore fluid diffusion as an incubation process for delayed failure triggering. Citation: Schubnel,

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“…In both cases conditions were such that the local deformation mechanisms are probably dominated by dislocation creep (DE BRESSER and SPIERS, 1993;RENNER et al, 2002;RUTTER, 1974). Immediately below we compare the isostatic compaction data with previous studies on hot-pressed aggregates of monominerallic calcite to reveal some details of the effect of adding a second-phase.…”

Section: Discussionmentioning

confidence: 86%

Permeability Evolution During Non-linear Viscous Creep of Calcite Rocks

Xiao

Evans

Bernabé

2006

Pure appl. geophys.

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Permeability, storage capacity and volumetric strain were measured in situ during deformation of hot-pressed calcite aggregates containing 10, 20, and 30 wt% quartz. Both isostatic and conventional triaxial loading conditions were used. The tests were performed at confining pressure of 300 MPa, pore pressures between 50 to 290 MPa, temperatures from 673 to 873 K and strain rates of 3 · 10 )5 s )1 . Argon gas was used as the pore fluid. The initial porosities of the starting samples varied from 5% to 9%, with higher porosity correlated to higher quartz content. Microstructural observations after the experiment indicate two kinds of pores are present: 1) Angular, crack-like pores along boundaries between quartz grains or between quartz and calcite grains and 2) equant and tubular voids within the calcite matrix. Under isostatic loading conditions, the compaction rate covaries with porosity and increases with increasing effective pressure. Most of the permeability reduction induced during compaction is irreversible and probably owes to plastic processes. As has been found in previous studies on hot-pressed calcite aggregates, permeability, k, is nonlinearly related to porosity, /. Over small changes in porosity, the two parameters are approximately related as k / / n . The exponent n strongly increases as porosity decreases to a finite value (from about 4 to 6% depending on quartz content), suggesting a porosity percolation threshold. When subjected to triaxial deformation, the calcite-quartz aggregates exhibit shearenhanced compaction, but permeability does not decrease as rapidly as it does under isostatic conditions. During triaxial compaction the exponent n only varies between 2 and 3. Non-isostatic deformation seems to reduce the percolation threshold, and, in fact, enhances the permeability relative to that at the same porosity during isostatic compaction. Our data provide constraints on the governing parameters of the compaction theory which describes fluid flow through a viscous matrix, and may have important implications for expulsion of sedimentary fluids, for fluid flow during deformation and metamorphism, and melt extraction from partially molten rocks.

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Dislocation creep of calcite

Cited by 91 publications

References 57 publications

Strain localization in the Morcles nappe (Helvetic Alps, Switzerland)

Strain localization in the Morcles nappe (Helvetic Alps, Switzerland)

Transient creep, aseismic damage and slow failure in Carrara marble deformed across the brittle‐ductile transition

Permeability Evolution During Non-linear Viscous Creep of Calcite Rocks

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