On the mechanism of dislocation creep of calcite at high temperature: Inferences from experimentally measured pressure sensitivity and strain rate sensitivity of flow stress

Abstract

[1] Previous laboratory experiments on coarse grained calcite materials at intermediate conditions of stress and temperature have shown low strain rate sensitivity of flow stress, expressed by standard power law stress exponents n ! 7. This conflicts with conventional models for creep controlled by dislocation climb (n = 3-4.5), a recovery mechanism widely used to explain steady-state dislocation creep. This paper addresses the question whether dislocation cross slip rather than climb is the mechanism controlling creep of calcite at intermediate conditions. New uniaxial compression tests were performed on calcite single crystals and Carrara marble at T = 800-1000°C, _ e = 10 À4 -2 Â 10 À7 s À1, and P = 100-600 MPa. Emphasis was on the pressure (P) and strain rate (_ e) sensitivity of flow stress, because these form potential ways for discriminating between climb and cross slip models. Both single crystals and Carrara marble demonstrated a small increase in flow stress with increasing pressure ($1.6% per 100 MPa) at constant strain rate and temperature. The low strain rate sensitivity of flow stress was confirmed, though n gradually changes with stress or temperature rather than taking a constant value. Evaluation of the experimental data against microphysical models indicated that cross slip controlled by dissociation of dislocations offers the best explanation for the observed mechanical behavior. If the associated creep equation is used to estimate flow stresses under natural conditions, the resulting values at T < 500°C are substantially less than those following from previous flow laws. The influence of pressure on the behavior of marble, however, can be safely ignored for most practical purposes.INDEX TERMS: 3902 Mineral Physics: Creep and deformation; 3904 Mineral Physics: Defects; 5120 Physical Properties of Rocks: Plasticity, diffusion, and creep; 8159 Tectonophysics: Evolution of the Earth: Rheology-crust and lithosphere; KEYWORDS: calcite, dislocation cross slip, pressure, creep Citation: De Bresser, J. H. P., On the mechanism of dislocation creep of calcite at high temperature: Inferences from experimentally measured pressure sensitivity and strain rate sensitivity of flow stress,

The influence of dynamic recrystallization on the grain size distribution and rheological behaviour of Carrara marble deformed in axial compression

“…Rather, it has been suggested that deformation of marble under conditions similar to those investigated in the present study is controlled by cross slip of dislocations (De Bresser & Spiers 1990). A detailed evaluation of mechanical data for calcite against dislocation cross-slip models is beyond the scope of this paper, but is the subject of a separate study that includes new deformation experiments on Carrara marble (see De Bresser 2002). In this separate study, cross slip is presented as a mechanism capable of dislocation recovery (as is dislocation climb), that thus prevents continuous work hardening (Poirier 1976;De Bresser 1991).…”

Mechanical behavior and microstructure of simulated calcite fault gouge sheared at 20–600°C: Implications for natural faults in limestones

“…An extensive data set exists on the rheology of dense calcite polycrystals in the temperature range of 300°C to 1000°C [ Rutter , ; Schmid et al ., , ; Walker et al ., ; De Bresser , ; De Bresser et al ., ; Renner et al ., ; Herwegh et al ., ], resulting in relatively well‐constrained deformation mechanism maps (DMMs) for calcite [e.g., Herwegh et al ., ; Rogowitz et al ., ]. Despite the important differences in experimental and sample characters between our tests and those reported in the abovementioned studies (water‐saturated gouge versus relatively dry dense polycrystals), a comparison of the predicted rheology of dense calcite polycrystals with the experimental conditions imposed in our experiments may help to elucidate the processes that played a role in our experiments at T ≈ 400–600°C.…”

“…[] for the grain size‐sensitive (GSS) field and by Walker et al . [] for the GSS + grain size‐insensitive (GSI) field and using the experimental data of De Bresser [] fitted to an exponential‐type flow equation [ Rutter , ; Schmid et al ., ] to represent the GSI field (Figure ) [see Appendix A; for a summary of GSI and GSS mechanisms, see Herwegh et al ., ]. These flow laws were determined for axial compression.…”

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

“…Also note that, at the temperatures and grain sizes investigated in the Morcles nappe, the paleopiezometer calibrations of schmid et al (1980) and rutter (1995) bound the predictions of the paleowattmeter, when the dislocation creep flow law of renner et al (2002) (rp) is used. Variations in the stress predicted by the several piezometers may arise owing to differences in technique used to the measure grain size (rutter 1995;De bresser 2002). In this study, we simply use the reported grain-size values, without attempting to resolve differences in techniques.…”