Influence of water fugacity and activation volume on the flow properties of fine‐grained anorthite aggregates

Rybacki, E.; Gottschalk, Matthias; Wirth, Richard; Dresen, Georg

doi:10.1029/2005jb003663

Cited by 181 publications

(186 citation statements)

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“…Temperature steps of 10°C-20°C performed on individual samples yield a significantly higher mean value of 371 ± 76 kJ mol −1 and an increase of Q with increasing temperature. This activation energy is close to the value of ≈350 kJ mol −1 obtained for dislocation creep of wet fine-grained anorthite aggregates [Rybacki and Dresen, 2000;Rybacki et al, 2006]. However, the dislocation density after deformation is similar to the starting material.…”

Section: Deformation Mechanismmentioning

confidence: 56%

“…"Wet" samples are assumed to be water-saturated at experimental conditions. Further details of sample preparation and characterization are described in the works of Rybacki and Dresen [2000] and Rybacki et al [2006]. The water content of starting material and deformed samples was similar within error bars, indicating that no water was lost during the runtime of the experiments.…”

Section: Starting Materialsmentioning

confidence: 89%

“…This precludes estimating water content in the grain interior. We expect higher water content along grain boundaries based on measurements of embedded anorthite single crystals in similar starting material [Rybacki et al, 2006]. "Wet" samples are assumed to be water-saturated at experimental conditions.…”

Section: Starting Materialsmentioning

confidence: 99%

“…Feldspar forms the major mineral constituent of rocks in the lower continental crust. Several experimental studies were recently conducted to examine the high-temperature rheology of fine-grained pure feldspar aggregates [Tullis and Yund, 1991;Tullis et al, 1996;Dimanov et al, 1998;Dimanov et al, 1999;Rybacki and Dresen, 2000;Rybacki et al, 2006]. These previous experiments were performed in triaxial compression at low axial strain < 30%.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Rybacki¹,

Wirth²,

Dresen³

2010

J. Geophys. Res.

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[1] We performed high-strain torsion experiments on fine-grained (≈4 mm) anorthite aggregates in a Paterson-type gas deformation apparatus. The dense hydrous (≈0.1 wt% H 2 O) samples contain < 3 vol% Si-enriched residual glass located at triple junctions. Specimens were twisted at constant rate to a maximum shear strain of about 5 at experimental conditions of 100-400 MPa confining pressure, temperatures of 950°C-1200°C, and shear strain rates of ≈2 × 10 −5 , 5 × 10 −5 , and 2 × 10 −4 s −1 . Resulting maximum shear stresses at the sample periphery were in the range of ≈2-80 MPa. The samples showed strain hardening at slow deformation rate and strain weakening at fast strain rate, respectively. Fitting the stress strain rate data to a power law yields linear viscous behavior. Microstructural analysis shows locally enhanced dislocation density, suggesting diffusion-assisted and/or dislocation-assisted grain boundary sliding as the dominant deformation mechanism. Deformed samples exhibit abundant cavities, nucleated mostly at grain triple junctions and at grain boundaries in response to cooperative grain boundary sliding. At shear strains ≥ 2, growth and coalescence of the cavities form an anastomozing network of regularly spaced strings oriented at about 30°to the direction of maximum compressive stress and ∼15°to the shear plane. Strain is localized along these shear bands associated with a shape-preferred orientation of high-aspect ratio feldspar grains and with segregation of initial pore fluids (residual glass) into the bands. More than one third of the samples were deformed to terminal failure that occurred suddenly at shear strains of ≈3-5. The experiments indicate that cavitation damage may facilitate fluid flow and deep seismicity in highly strained shear zones.Citation: Rybacki, E., R. Wirth, and G. Dresen (2010), Superplasticity and ductile fracture of synthetic feldspar deformed to large strain,

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Section: Deformation Mechanismmentioning

confidence: 56%

Section: Starting Materialsmentioning

confidence: 89%

Section: Starting Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Rybacki¹,

Wirth²,

Dresen³

2010

J. Geophys. Res.

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“…C. G. Goetze (personal communication, 1975) proposed this to his colleagues, and the comparison of laboratory measurements and field-based observations of rock strength by Brace and Kohlstedt [1980] put the idea on a firm footing. Goetze's and Brace and Kohlstedt's logic was based largely on the different creep properties of quartz and olivine, but subsequent studies have shown feldspar to be somewhat weaker than olivine at the same temperatures, at least when both are enriched in hydrogen ("wet") Dresen, 2000, 2004;Rybacki et al, 2006]. Although it seems likely that in some regions, a "dry" lower crust over a "wet" uppermost mantle could make the lower crust the stronger, most imagine that a low-viscosity zone characterizes the lower or middle continental crust of tectonically active regions.…”

Section: Introductionmentioning

confidence: 99%

Effects of a low‐viscosity lower crust on topography and gravity at convergent mountain belts during gravitational instability of mantle lithosphere

Molnár

Houseman

2015

JGR Solid Earth

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We examine the gravitational stability of a stratified structure consisting of a low-density crust through which viscosity decreases exponentially, over a denser mantle lithosphere of constant viscosity, which in turn overlies an inviscid, slightly less dense layer like the asthenosphere. The most important aspect of the viscosity structure is the contrast in viscosity at the Moho. Surface uplift above a mantle downwelling is greatest when the viscosity contrast at the Moho is negligible. The surface is depressed when the viscosity of the lowermost crust is much greater than mantle viscosity. For a wide range of viscosity structures, calculated gravity anomalies and in particular admittances (ratios of the Fourier transform of gravity to that of topography) produced by Rayleigh-Taylor instability differ markedly from those observed across convergent mountain belts. In particular, whereas values of calculated admittance are negative, or very small, observed admittances are consistently positive. Thus, if downwelling of mantle lithosphere directly beneath mountain ranges plays an important role in the construction of mountain belts, it cannot be the main process that induces crustal thickening.

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A friction to flow constitutive law and its application to a 2‐D modeling of earthquakes

Shimamoto

Noda

2014

JGR Solid Earth

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Establishment of a constitutive law from friction to high-temperature plastic flow has long been a challenging task for solving problems such as modeling earthquakes and plate interactions. Here we propose an empirical constitutive law that describes this transitional behavior using only friction and flow parameters, with good agreements with experimental data on halite shear zones. The law predicts steady state and transient behaviors, including the dependence of the shear resistance of fault on slip rate, effective normal stress, and temperature. It also predicts a change in velocity weakening to velocity strengthening with increasing temperature, similar to the changes recognized for quartz and granite gouge under hydrothermal conditions. A slight deviation from the steady state friction law due to the involvement of plastic deformation can cause a large change in the velocity dependence. We solved seismic cycles of a fault across the lithosphere with the law using a 2-D spectral boundary integral equation method, revealing dynamic rupture extending into the aseismic zone and rich evolution of interseismic creep including slow slip prior to earthquakes. Seismic slip followed by creep is consistent with natural pseudotachylytes overprinted with mylonitic deformation. Overall fault behaviors during earthquake cycles are insensitive to transient flow parameters. The friction-to-flow law merges "Christmas tree" strength profiles of the lithosphere and rate dependency fault models used for earthquake modeling on a unified basis. Strength profiles were drawn assuming a strain rate for the flow regime, but we emphasize that stress distribution evolves reflecting the fault behavior. A fault zone model was updated based on the earthquake modeling.

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Influence of water fugacity and activation volume on the flow properties of fine‐grained anorthite aggregates

Cited by 181 publications

References 62 publications

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Effects of a low‐viscosity lower crust on topography and gravity at convergent mountain belts during gravitational instability of mantle lithosphere

A friction to flow constitutive law and its application to a 2‐D modeling of earthquakes

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