The effect of dissolved magnesium on diffusion creep in calcite

Herwegh, Marco; Xiao, Xiaohui; Evans, Brian

doi:10.1016/s0012-821x(03)00284-x

Cited by 74 publications

(131 citation statements)

References 38 publications

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“…Some grains show relatively straight grain boundaries, equilibrium angles at neighboring grain triple junctions, and abundant dislocations, often close to grain boundaries. Weak crystallographic textures of deformed magnesio-calcite may indicate grain boundary sliding (GBS) as an important deformation mechanism (Raj and Ashby 1971;Gifkins 1976), which agrees with triaxial deformation experiments on polycrystalline magnesio-calcite samples (Herwegh et al 2003). Herwegh et al (2003) suggested a combination of grain boundary sliding and grain boundary diffusion creep at temperatures between 750 and 800 °C and stresses <40 MPa, almost independent of magnesium content.…”

Section: Deformation Mechanisms and Strengthsupporting

confidence: 71%

“…Weak crystallographic textures of deformed magnesio-calcite may indicate grain boundary sliding (GBS) as an important deformation mechanism (Raj and Ashby 1971;Gifkins 1976), which agrees with triaxial deformation experiments on polycrystalline magnesio-calcite samples (Herwegh et al 2003). Herwegh et al (2003) suggested a combination of grain boundary sliding and grain boundary diffusion creep at temperatures between 750 and 800 °C and stresses <40 MPa, almost independent of magnesium content. In the high-strain part of twisted samples, magnesio-calcite grains show dislocation walls forming low-angle grain boundaries, implying a non-conservative movement of dislocations via climb.…”

Section: Deformation Mechanisms and Strengthsupporting

confidence: 71%

“…Large magnesio-calcite grains next to pure calcite show convex grain boundaries and often straight boundaries with neighboring grains including 120° triple junctions. The curved grain boundaries of magnesiocalcite toward pure calcite indicate that growth of grains occurs by chemically induced grain boundary migration accompanied by diffusion processes (Evans et al 1986;Herwegh et al 2003).…”

Section: Reaction Rim Microstructuresmentioning

confidence: 99%

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Influence of stress and strain on dolomite rim growth: a comparative study

Helpa

Rybacki

Morales

et al. 2015

Contrib Mineral Petrol

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Section: Deformation Mechanisms and Strengthsupporting

confidence: 71%

Section: Deformation Mechanisms and Strengthsupporting

confidence: 71%

Section: Reaction Rim Microstructuresmentioning

confidence: 99%

See 1 more Smart Citation

Influence of stress and strain on dolomite rim growth: a comparative study

Helpa

Rybacki

Morales

et al. 2015

Contrib Mineral Petrol

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“…Strain rates in diffusion creep and GBS are therefore highly sensitive to grain size, which is supported by experimental data Herwegh et al, 2003;Xu et al, 2009;Rogowitz et al, 2015).…”

Section: Strain Rate Laws and Deformation Mapssupporting

confidence: 52%

“…For dislocation creep, values for n range between 3 and 9 (Herwegh et al, 2003) and m varies but is always lower than diffusion and can approach zero (i.e. insensitive to grain size) or turn negative (i.e.…”

Section: Strain Rate Laws and Deformation Mapsmentioning

confidence: 99%

Millimetre-Scale Localisation of Strain and Dissolution in Oolitic Grainstone

Lynch¹

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Millimetre-scale localisation of strain and dissolution in oolitic grainstone ii KeywordsCarbonate, clay dissolution, cement, CPO, ductile, deformation mechanisms, EBSD, grain boundary sliding, geological history, initial interfaces, microfabric, ooid, oolite, porosity, pressure solution, SPO, strain localisation, stylolite, viscosity, XFMMillimetre-scale localisation of strain and dissolution in oolitic grainstone iii AbstractLocalisation of finite strain in rocks is commonly explained by variations in loading conditions, rock mechanical properties and rock fabric. In a geological sequence of layered rocks where loading conditions (such as temperature and far-field stress) are similar, strain variations are commonly constrained to layers with differing material properties. The examined Gudman Oolite presents a unique and interesting example of how variable finite strain is influenced by minor variations in material properties.The Carboniferous Gudman Oolite features alternating millimetre-to centimetre-thick layers of coarse ooids (mean diameter ~1-3mm) and fine ooids (mean diameter ~0.5-1mm) within a sparitic cement (30-300µm grains). Each layer is predominantly (>95%) calcite, formed in the same depositional environment and experienced the same tectonic history. However, the coarse-ooid layers show high non-coaxial deformation and extensive stylolite textures. In contrast, the fine-ooid layers appear nearly undeformed, and are almost devoid of dissolution textures.To shed light on the reasons for this marked localisation of deformation and dissolution, the rock mechanical properties and rock fabric were measured using a combination of X-ray Fluorescence Microscopy (XFM), Electron Backscatter Diffraction (EBSD), X-ray Diffraction (XRD), palaeotemperature analysis and petrographic methods including Scanning Electron Microscopy (SEM), Cathodoluminescence (CL) and transmitted light microscopy. Examination of overprinting relationships in the coarse-ooid layer shows that localised dissolution (D1) occurred prior to localised non-coaxial strain (D2). Primitive stylolite textures suggest that dissolution seams formed in concentric mica-rich layers within ooids which occasionally linked to surrounding ooids to form laterally extensive stylolite seams. I argue that the relatively larger ooids in the coarse-ooid layer contain more extensive micaceous layers which promoted linking and dissolution to form laterally continuous stylolite seams.I conclude that D1 dissolution destroyed the C3 cement framework and reduced the strength of the coarse-ooid layer relative to the largely preserved fine-ooid layer. The later D2 shear deformation event localised strain in the weakened coarse-ooid layer.

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The Minimized Power Geometric model: An analytical mixing model for calculating polyphase rock viscosities consistent with experimental data

2014

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Here we introduce the Minimized Power Geometric (MPG) model which predicts the viscosity of any polyphase rocks deformed during ductile flow. The volumetric fractions and power law parameters of the constituting phases are the only model inputs required. The model is based on a minimization of the mechanical power dissipated in the rock during deformation. In contrast to existing mixing models based on minimization, we use the Lagrange multipliers method and constraints of strain rate and stress geometric averaging. This allows us to determine analytical expressions for the polyphase rock viscosity, its power law parameters, and the partitioning of strain rate and stress between the phases. The power law bulk behavior is a consequence of our model and not an assumption. Comparison of model results with 15 published experimental data sets on two-phase aggregates shows that the MPG model reproduces accurately both experimental viscosities and creep parameters, even where large viscosity contrasts are present. In detail, the ratio between experimental and MPG-predicted viscosities averages 1.6. Deviations from the experimental values are likely to be due to microstructural processes (strain localization and coeval other deformation mechanisms) that are neglected by the model. Existing models that are not based on geometric averaging show a poorer fit with the experimental data. As long as the limitations of the mixing models are kept in mind, the MPG model offers great potential for applications in structural geology and numerical modeling.

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The effect of dissolved magnesium on diffusion creep in calcite

Cited by 74 publications

References 38 publications

Influence of stress and strain on dolomite rim growth: a comparative study

Influence of stress and strain on dolomite rim growth: a comparative study

Millimetre-Scale Localisation of Strain and Dissolution in Oolitic Grainstone

The Minimized Power Geometric model: An analytical mixing model for calculating polyphase rock viscosities consistent with experimental data

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