Dislocation and diffusion creep of synthetic anorthite aggregates

Rybacki, E.; Dresen, Georg

doi:10.1029/2000jb900223

Cited by 264 publications

(303 citation statements)

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“…Previously, Garrick-Bethell et al (2010) 16 (their Supporting Online Material Section 6) found that significant crustal flow was not likely to take place in less than 150 By. In those calculations, they used a creep flow law from Rybacki and Dresen (2000) 43 , with stress exponent n = 3 (indicating nonNewtonian dislocation creep), and an assumed basal temperature of 1175° C. However, in the present study, we calculated tidal heating cases with higher temperatures (Table S13). As described in the main text and Section S8.1, there are many uncertainties in the properties of the early crust, and while some temperatures we use may not be achieved, they illustrate the effect of progressively higher tidal heat fluxes on the shape parameters C 2,0 and C 2,2 .…”

Section: S82 -Lower Crustal Flowmentioning

confidence: 99%

“…Rybacki and Dresen (2000) 43 found that dry anorthosite likely flows via diffusion (Newtonian flow n = 0, m = 3) or dislocation creep (non-Newtonian, n = 3, m = 0), depending on σ and T. The driving stress for crustal flow is  Δρhg, where here Δρ is the crust-ocean density contrast, h is the thickness contrast, and g is gravity. For Δρ = 300 kg/m 3 and h = 10 km, σ  5 MPa.…”

Section: S82 -Lower Crustal Flowmentioning

confidence: 99%

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The tidal–rotational shape of the Moon and evidence for polar wander

Garrick‐Bethell

Perera

Nimmo

et al. 2014

Nature

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Summary paragraph: The origin of the Moon's large-scale topography is important for understanding lunar geology 1 , lunar orbital evolution 2 , and the Moon's orientation in the sky 3 .Previous hypotheses for its origin have included late accretion events 4 , large impacts 5 , tidal effects 6 , and convection processes 7 . However, testing these hypotheses and quantifying the Moon's topography is complicated by the large basins that have formed since the crust crystallized. Here we estimate the low-order lunar topography and gravity spherical harmonics outside these basins and show that the bulk of the degree-2 topography is consistent with a crustbuilding process controlled by early tidal heating throughout the Moon. The remainder of the degree-2 topography is consistent with a frozen tidal-rotational bulge that formed later, at a semimajor axis of 32 Earth radii. The probability of the degree-2 shape having these two separate tidal characteristics by chance is less than 1%. We also infer that internal density contrasts eventually reoriented the Moon's polar axis 36  4°, to the present configuration we observe today. Together, these results link the geology of the near and far sides, and resolve longstanding questions about the Moon's low-order shape, gravity, and history of polar wander. 2 Main TextThe theory of equilibrium figures of rotating fluid bodies is a classic problem in geophysics, and it has been helpful in understanding the shapes of the Sun and planets. However, the origin for the Moon's shape has remained an open problem in the last century 2,6,[8][9][10] , and the body's deviations from any simple tidal-rotational (spherical harmonic degree-2) figure are large 11 . This difficulty is surprising given the Moon's presumably simple early thermal history: born hot and quickly cooled, one might expect the Moon to be described by a simple figure of equilibrium.Researchers have traditionally suggested that the Moon's degree-2 spherical harmonic gravity coefficients, which have been used as proxies for the degree-2 shape, are especially large when compared to higher degree coefficients 9,12 . Figure 1 shows a power law or "Kaula's rule" fit to degrees n = 3 to 50 for the Moon's gravity 13 and topography data 14 . The power at degree 2 is 4.5 times and 2.6 times the power expected from extrapolating the best-fit power law, for gravity and topography, respectively, supporting the idea that the degree-2 coefficients are unique. Indeed, the fraction of excess power for topography is greater than the excesses for Venus, Earth, and Mars (SI). Authors have tried to interpret the Moon's strong degree-2 power as a frozen tidalrotational state inherited from when the Moon was closer to the Earth, known as the fossil bulge hypothesis 6 . An open problem, however, has been that the ratio of the C 2,0 and C 2,2 spherical harmonic coefficients is different from the expected value by a factor of 2. 6 (refs. 2,10).Adding to the fossil bulge idea and motivated by tidal processes in Europa's ice shell 15 , GarrickBet...

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Section: S82 -Lower Crustal Flowmentioning

confidence: 99%

Section: S82 -Lower Crustal Flowmentioning

confidence: 99%

The tidal–rotational shape of the Moon and evidence for polar wander

Garrick‐Bethell

Perera

Nimmo

et al. 2014

Nature

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“…Based on laboratory data (Rybacki and Dresen, 2000) that show a relatively strong rheology ("normal" models), we consider another two cases of lower crust viscosity with weaker rheology at the same temperature and stress. In the "weak" and "weakest" models, the parameter B n in the expression for dislocation creep (eq.…”

Section: Model Parametersmentioning

confidence: 99%

“…(1) Gleason and Tullis (1995) (2) Rybacki and Dresen (2000) (3) Hirth and Kohlstedt (1996) Source for diffusion and Peierls' creep laws in mantle: Kameyama et al (1999).…”

Section: Figure Captionsmentioning

confidence: 99%

Three-dimensional numerical models of the evolution of pull-apart basins

Petrunin¹,

Sobolev²

2008

Physics of the Earth and Planetary Interiors

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To cite this version:A.G. Petrunin, S.V. Sobolev. Three-dimensional numerical models of the evolution of pullapart basins. Physics of the Earth and Planetary Interiors, Elsevier, 2008, 171 (1-4) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1

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“…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%

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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Dislocation and diffusion creep of synthetic anorthite aggregates

Cited by 264 publications

References 84 publications

The tidal–rotational shape of the Moon and evidence for polar wander

The tidal–rotational shape of the Moon and evidence for polar wander

Three-dimensional numerical models of the evolution of pull-apart basins

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

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