Grain-size-sensitive flow and shear-stress enhancement at the brittle–ductile transition of the continental crust

Gueydan, Frédéric; Leroy, Yves M.; Jolivet, Laurent

doi:10.1007/s005310000160

Cited by 25 publications

(22 citation statements)

References 40 publications

(60 reference statements)

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“…Regarding the physical mechanism of plastic flow, in this study, we considered both diffusion creep and dislocation creep. For a given mineral, we assume that the same shear stress controls the two deformation mechanisms (e.g., Gueydan et al 2001;Montési and Hirth 2003). Under this assumption, the total strain rate ε total is expressed as the sum of the diffusion creep strain rate ε diff and the strain rate caused by dislocation creep ε disl .…”

Section: Rheologymentioning

confidence: 99%

Shear strain concentration mechanism in the lower crust below an intraplate strike-slip fault based on rheological laws of rocks

Zhang

Sagiya

2017

Earth Planets Space

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We conduct a two-dimensional numerical experiment on the lower crust under an intraplate strike-slip fault based on laboratory-derived power-law rheologies considering the effects of grain size and water. To understand the effects of far-field loading and material properties on the deformation of the lower crust on a geological time scale, we assume steady fault sliding on the fault in the upper crust and ductile flow for the lower crust. To avoid the stress singularity, we introduce a yield threshold in the brittle-ductile transition near the down-dip edge of the fault. Regarding the physical mechanisms for shear strain concentration in the lower crust, we consider frictional and shear heating, grain size, and power-law creep. We evaluate the significance of these mechanisms in the formation of the shear zone under an intraplate strike-slip fault with slow deformation. The results show that in the lower crust, plastic deformation is possible only when the stress or temperature is sufficiently high. At a similar stress level, ∼100 MPa, dry anorthite begins to undergo plastic deformation at a depth around 28-29 km, which is about 8 km deeper than wet anorthite. As a result of dynamic recrystallization and grain growth, the grain size in the lower crust may vary laterally and as a function of depth. A comparison of the results with constant and nonconstant grain sizes reveals that the shear zone in the lower crust is created by power-law creep and is maintained by dynamically recrystallized material in the shear zone because grain growth occurs in a timescale much longer than the recurrence interval of intraplate earthquakes. Owing to the slow slip rate, shear and frictional heating have negligible effects on the deformation of the shear zone. The heat production rate depends weakly on the rock rheology; the maximum temperature increase over 3 Myr is only about several tens of degrees.

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Section: Rheologymentioning

confidence: 99%

Shear strain concentration mechanism in the lower crust below an intraplate strike-slip fault based on rheological laws of rocks

Zhang

Sagiya

2017

Earth Planets Space

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“…Various phenomena can accelerate strain softening, such as shear heating, grain size reduction, metamorphic reactions, or fl uid circulation (White and Knipe, 1978;Marquer et al, 1985;Tullis and Yund, 1985;Wintsch et al, 1995;Gueydan et al, 2001;Gueydan et al, 2003); however, these mechanisms can work only once a certain degree of localization has occurred and has created channels. The initial processes for localizing deformation are yet to be described.…”

Section: Introductionmentioning

confidence: 97%

Strain localization during crustal-scale boudinage to form extensional metamorphic domes in the Aegean Sea

Jolivet¹,

Famin²,

Mehl³

et al. 2004

Gneiss Domes in Orogeny

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159

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Post-orogenic extension in the Aegean Sea has produced several metamorphic domes. Some domes ("b-type") are elongated perpendicular to the main N-S direction of extension, and they correspond to the exhumation of the middle crust along northdipping detachments. The example of Tinos shows the progressive localization of deformation from the initial boudinage at all scales to the formation of brittle structures at the tips of boudins and the selection of one of those, which becomes the main detachment. The progressive deformation leading to strain localization is described alongside the P-T-t evolution and the role of fl uid circulation. The second type of domes ("a-type") has a long axis parallel to the direction of extension. Extension is accommodated by a detachment that exhumes high-temperature gneisses issued from deeper parts of the Hellenic edifi ce. Shortening perpendicular to stretching has produced the extension-parallel folds that are also observed in b-type domes but to a lesser extent. The formation of b-type and then a-type domes during extension is discussed in terms of crustal collapse during slab retreat.

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“…To date there are only very few modeling approaches oriented in this direction. Pioneering work for investigating the relation between damage by brittle cracking and aseismic creep has been proposed (LYAKHOVSKY et al, 2005;LYAKHOVSKY and BEN-ZION, 2008), the role of crustal phase transition and grain size reduction have been investigated by (GUEYDAN et al, 2001; and the feedback between brittle instabilities by thermal-expansion and shear-heating and ductile instabilities by shearheating and accelerated creep have been presented YUEN, 2006, 2008). The latter point, thermal-mechanical coupling via shear-heating in fault zones has been stressed many times since DAVE GRIGGS (1969) as a key to the understanding of geodynamical processes.…”

Section: Instabilities In Crustal Deformationmentioning

confidence: 99%

Landslides, Ice Quakes, Earthquakes: A Thermodynamic Approach to Surface Instabilities

Regenauer-Lieb

Yuen

Fußeis

2009

Pure appl. geophys.

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The total rate of rock deformation results from competing deformation processes, including ductile and brittle mechanisms. Particular deformation styles arise from the dominance of certain mechanisms over others at different ambient conditions. Surprisingly, rates of deformation in naturally deformed rocks are found to cluster around two extremes, representing coseismic slip rates or viscous creep rates. Classical rock mechanics is traditionally used to interpret these instabilities. These approaches consider the principle of conservation of energy. We propose to go one step further and introduce a nonlinear far-from-equilibrium thermodynamic approach in which the central and explicit role of entropy controls instabilities. We also show how this quantity might be calculated for complex crustal systems. This approach provides strain-rate partitioning for natural deformation processes occurring at rates in the order of 10 -3 to 10 -9 s -1 . We discuss these processes using examples of landslides and ice quakes or glacial surges. We will then illustrate how the mechanical mechanisms derived from these near-surface processes can be applied to deformation near the base of the seismogenic crust, especially to the phenomenon of slow earthquakes.

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Grain-size-sensitive flow and shear-stress enhancement at the brittle–ductile transition of the continental crust

Abstract: Localized shear zones along low-angle normal faults have been identified in regions of extension at the brittle±ductile transition of the continental crust.

Cited by 25 publications

References 40 publications

Shear strain concentration mechanism in the lower crust below an intraplate strike-slip fault based on rheological laws of rocks

Shear strain concentration mechanism in the lower crust below an intraplate strike-slip fault based on rheological laws of rocks

Strain localization during crustal-scale boudinage to form extensional metamorphic domes in the Aegean Sea

Landslides, Ice Quakes, Earthquakes: A Thermodynamic Approach to Surface Instabilities

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