Dynamic recrystallization and strain softening of olivine aggregates in the laboratory and the lithosphere

Drury, M. R.

doi:10.1144/gsl.sp.2005.243.01.11

Cited by 54 publications

(55 citation statements)

References 67 publications

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“…The values for σ t span a wide range: 2 · 10 6 − 3 · 10 9 Pa, comparable to the transition stresses in figure 6 from Drury (2005). Nevertheless, once the power-law behavior is dominant at higher stresses, the right panel of figure 1 shows that the rheology follows a narrow band for all tested parameters.…”

Section: Average Ductile Lithosphere Rheologysupporting

confidence: 69%

“…Poirier (1980); Bercovici and Karato (2002)), by mechanisms such as recrystallization (Karato et al, 1980) or shear heating (Regenauer-Lieb and Yuen, 1998). The amount of weakening or strengthening due to strain softening or hardening, respectively, in shear zones is however debated (De Bresser et al, 2001;Drury, 2005;Platt and Behr, 2011;Tasaka et al, 2017). Alternatively, in settings with highly varying stresses, power-law creep may result in high rates of deformation, as the strain rate will localize stronger than the stress itself.…”

Section: Introductionmentioning

confidence: 99%

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New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

Broerse¹,

Norder²,

Govers³

et al. 2018

Preprint

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Stress-dependent nonlinear upper mantle rheology has a firm base in rock mechanical tests, where this nonlinearity results from dislocation creep of minerals. In the last few decades there has been some attention to nonlinear, power-law, materials for application in scaled analogue experiments for tectonic processes. However, studies describing the rheology of analogue materials with the same nonlinear dependency on stress as observed for lithospheric mantle materials at relevant stress levels, are still lacking.In this study we have developed and rheologically tested materials based on combinations of silicone polymers and plasticine, with the aim of obtaining a material that can serve as a laboratory analogue to the power-law rheology of olivine aggregates at lithospheric mantle conditions. From our steadystate creep tests we find that it is possible to obtain such a power-law material, with effective viscosities over relevant model stress ranges We apply the developed material to a process where localized deformation of the lithosphere can be expected: slab break-off. We study this process using analogue models, where we apply the new nonlinear material to the lithospheric mantle domains, while we use Newtonian glucose to represent the low viscous asthenosphere. Now that we properly manage power-law behavior in our analogue lithosphere materials, we are able to model localized lithospheric tearing.

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Section: Average Ductile Lithosphere Rheologysupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

Broerse¹,

Norder²,

Govers³

et al. 2018

Preprint

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“…In naturally deformed mantle rocks, strain localisation is typically associated with grain size reduction and a switch from grain size-insensitive creep to grain sizesensitive creep (Drury, 2005). Recent observations on natural samples highlighted the importance of the grain-size-dependent dislocation-accommodated grain boundary sliding (disGBS) of olivine as controlling the rheology of mantle shear zone (Précigout et al, 2007;Warren and Hirth, 2006).…”

Section: / Geological Constraintsmentioning

confidence: 99%

“…Based on field observations in the Ronda peridotite (southern Spain) and the experimental data of Hirth and Kohlstedt (2003), Précigout et al (2007) proposed a strain-dependent mantle rheology in which the overall strain rate ̇ is the sum of four ductile deformation mechanisms: dislocation creep ( ̇), diffusion creep ( ̇), disGBS ( ̇) and exponential creep ( ̇) (Hirth and Kohlstedt, 2003;Drury, 2005;Précigout et al, 2007). Each mechanism contributes to the bulk strain rate ( ) of an olivine aggregate according to:…”

Section: / Mantle Rheologymentioning

confidence: 99%

“…To date, shear heating has probably received the most extensive theoretical treatment (Brun and Cobbold, 1980; Fleitout and Froidevaux, 1980; Regenauer-Lieb and Yuen, 1998;Kaus and Podladchikov, 2006;Crameri and Kaus, 2010). However, field observations indicate that metamorphic reactions, fluid infiltration and grain size reduction play a crucial role in enabling shear localization (Poirier, 1980;Park et al, 2006;Wintsch et al, 1995; Warren et al, 1996;Gueydan et al, 2003;Drury, 2005;Gerbi et al, 2010;Toy et al, 2010;Platt and Behr, 2011; Rennie et al, 2013;Sullivan et al, 2013). It is thus important to characterize the rheological effect of these processes.…”

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confidence: 99%

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Strain weakening enables continental plate tectonics

2014

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Much debate exists concerning the strength distribution of the continental lithosphere, how it controls lithosphere-scale strain localization and hence enables plate tectonics. No rheological model proposed to date is comprehensive enough to describe both the weakness of plate boundary and rigid-like behaviour of plate interiors. Here we show that the duality of strength of the lithosphere corresponds to different stages of microstructural evolution. Geological constraints on lithospheric strength and large strain numerical experiments reveal that the development of layers containing weak minerals and the onset of grain boundary sliding upon grain size reduction in olivine cause strain localisation and reduce strength in the crust and subcontinental mantle, respectively. The positive feedback between weakening and strain localization leads to the progressive development of weak plate boundaries while plate interiors remain strong. 2 1/ IntroductionThe extrapolation of laboratory flow laws to geological scale suggests a complex layering of brittle and ductile layers within the continental lithosphere (Brace and Kohlstedt, 1980;Sawyer, 1985). For classical continental geotherm, the upper lithospheric mantle is expected to be brittle and support high stresses. Many analogue and numerical experiments indicate that such a rheological layering is important to reproduce first-order patterns of lithosphere deformation (Brun, 1999;Burov and Yamato, 2008). In particular, the presence of a brittle uppermost mantle is needed to explain strain localisation at lithospheric scale (Buck, 1991;Gueydan et al., 2008).However, recent geophysical studies question this classical view of the continental strength layering. Based on earthquakes distribution and elastic thicknesses of the continental lithosphere, including cratons, it has been proposed that the uppermost mantle could behave as ductile instead of brittle (Déverchère et al., 2001;Jackson, 2002;Maggi et al., 2000). However, the mechanical stability of cratons requires that the uppermost mantle supports high stresses (Burov, 2010). In addition, the post-seismic displacement field, i.e., the pattern of deformation at the surface of the Earth within weeks to years following an earthquake, suggests that the deep crust is stronger than the lithospheric mantle. (Bürgmann and Dresen, 2008;Thatcher and Pollitz, 2008). Note however that post seismic displacement field may also result from a complex combination of poro-elasticity and fault creep in the seismogenic layer and viscous flow in the lower crust (Barbot and Fialko, 2010). In this case, it may not be used to constrain strength ratios between the ductile crust 3 and lithospheric mantle. Finally, the recent discovery of non-volcanic tremors, i.e., long duration seismic events with small amplitudes, below the San Andreas fault suggests a zone of localized and easily modulated faulting in the lower crust (Nadeau and Guilhem, 2009;Thomas et al., 2009). Assuming high temperatures in plate boundaries such as the San Andreas...

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Observations of grain size sensitive power law creep of olivine aggregates over a large range of lattice‐preferred orientation strength

et al. 2016

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Grain size sensitive (GSS) power law creep of San Carlos olivine aggregates was investigated by comparing strain rates measured in laboratory deformation experiments to strain rates determined from a micromechanical model of intragranular dislocation processes. The plastic flow behavior of olivine aggregates due solely to intragranular slip was determined using flow laws for olivine single crystals in combination with grain orientations measured by electron backscatter diffraction. Measured strain rates were compared to results from the micromechanical model for samples deformed in compression to an axial strain of <0.2 and in torsion to a shear strain of up to 7.4. Olivine aggregates deform up to a factor of 4.6 times faster than the maximum possible rates determined from the micromechanical model of intragranular slip. Comparison of our data to published flow laws indicates that diffusion creep cannot account for this difference. The ratio of experimentally determined strain rates to those from the micromechanical model is strongly dependent upon grain size but is independent of stress and strength of lattice‐preferred orientation. These observations indicate that GSS power law creep, consistent with dislocation‐accommodated grain boundary sliding, occurs in both weakly and strongly textured olivine aggregates at the studied conditions.

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Dynamic recrystallization and strain softening of olivine aggregates in the laboratory and the lithosphere

Abstract: The effects of dynamic recrystallization on the deformation mechanisms and

Cited by 54 publications

References 67 publications

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

Strain weakening enables continental plate tectonics

Observations of grain size sensitive power law creep of olivine aggregates over a large range of lattice‐preferred orientation strength

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