A few remarks on the kinetics of static grain growth in rocks

Evans, Brian; Renner, Jörg; Hirth, Greg

doi:10.1007/s005310000150

Cited by 259 publications

(255 citation statements)

References 58 publications

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“…Although diffusion creep depends on the evolving grain size, the interface between the rock's mineral phases (i.e., olivine and pyroxene) induces Zener pinning, which blocks grain growth (40)(41)(42). Thus, we assume grain size evolution is slaved to the evolution of the size of the pinning bodies r, which is equivalent to the characteristic radius of curvature, or roughness of the interface (27)(28)(29).…”

Section: Significancementioning

confidence: 99%

Abrupt tectonics and rapid slab detachment with grain damage

Bercovici

Schubert

Ricard

2015

Proc. Natl. Acad. Sci. U.S.A.

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A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.subduction zones | slab detachment | plate tectonics | continent rebound

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Section: Significancementioning

confidence: 99%

Abrupt tectonics and rapid slab detachment with grain damage

Bercovici

Schubert

Ricard

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The driving force for this process is usually derived from the specific surface energy (γ ) of the material and the local radius of curvature (r) of the grain boundary. This driving force is proportional to the reduction of the Gibbs free energy ( G) [25]. The energy for grain boundary migration derived from the reduction of the Gibbs free energy is largest for surfaces with a small radius of curvature (Equation 8).…”

Section: Grain Growthmentioning

confidence: 99%

“…In contrast to normal grain growth, abnormal grain growth can occur in aggregates where some large grains exist in an otherwise fine grained matrix. The larger grains will then grow at the cost of many small grains which will shrink or disappear [25].…”

Section: Grain Growthmentioning

confidence: 99%

“…Fluid films, inclusions, melt, pore size, and the chemical composition of fluids can all change the grain boundary mobility [24,25,33]. In our simulation we focus on the interaction of a second-phase volume fraction with a migrating grain boundary.…”

Section: Drag Force Of Mobile Particlesmentioning

confidence: 99%

“…In our simulation we focus on the interaction of a second-phase volume fraction with a migrating grain boundary. This second-phase can for example be fluid filled pores or a different mineral phase [23][24][25][33][34][35]. The interaction between the grain boundary and an impurity, which results in reduction of the driving force for migration, can be quantified by the so-called Zener drag.…”

Section: Drag Force Of Mobile Particlesmentioning

confidence: 99%

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Zebra pattern in rocks as a function of grain growth affected by second-phase particles

2015

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Alternating fine grained dark and coarse grained light layers in rocks are often termed zebra patterns and are found worldwide. The crystals in the different bands have an almost identical chemical composition, however second-phase particles (e.g., fluid filled pores or a second mineral phase) are concentrated in the dark layers. Even though this pattern is very common and has been studied widely, the initial stage of the pattern formation remains controversial. In this communication we present a simple microdynamic model which can explain the beginning of the zebra pattern formation. The two dimensional model consists of two main processes, mineral replacement along a reaction front, and grain boundary migration affected by impurities. In the numerical model we assume that an initial distribution of second-phase particles is present due to sedimentary layering. The reaction front percolates the model and redistributes second-phase particles by shifting them until the front is saturated and drops the particles again. This produces and enhances initial layering. Grain growth is hindered in layers with high second-phase particle concentrations whereas layers with low concentrations coarsen. Due to the grain growth activity in layers with low second-phase particle concentrations these impurities are collected at grain boundaries and the crystals become very clean. Therefore, the white layers in the pattern contain large grains with low concentration of second-phase particles, whereas the dark layers contain small grains with a large second-phase particle concentration. The presence of the zebra pattern is characteristic for regions containing Pb-Zn mineralization. Therefore, the origin of the structure is presumably related to the mineralization process and might be used as a marker for ore exploration. A complete understanding of the formation of this pattern will contribute to a more accurate understanding of hydrothermal systems that build up economic mineralization.

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Influence of mineral fraction on the rheological properties of forsterite + enstatite during grain size sensitive creep: 3. Application of grain growth and flow laws on peridotite ultramylonite

Tasaka

Hiraga

Michibayashi

2014

J. Geophys. Res. Solid Earth

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Microstructures of a layered peridotite ultramylonite from the Oman ophiolite are compared with that of experimentally deformed samples. Average grain sizes and grain size ratios of olivine and pyroxene from each layer are compared with respect to the fraction of pyroxene (f px ) in the layer. Grain size of the pyroxene is almost constant among different f px layers, whereas olivine grain size decreases significantly with increasing f px , both of which were characteristic features found in forsterite + enstatite aggregates after grain growth experiments . Furthermore, the Zener relationship (log d ol /d px versus log f px ) found in the ultramylonite is remarkably comparable to that observed in our experiments. These observations indicate effective pinning of olivine grain growth due to the presence of pyroxene grains during the deformation of the rocks. Olivine grains in layers with f px ≥ 0.03 do not exhibit lattice-preferred orientation (LPO), whereas the grains in layers with f px < 0.03 exhibit LPO, indicating that deformation proceeded via diffusion-and dislocation-accommodated creep in the former and the latter layers, respectively. We simulated the evolution of grain size and viscosity in the shear zone based on our grain growth and flow laws obtained for diffusion creep of forsterite + enstatite and successfully reproduced the observed grain sizes in the ultramylonite. We therefore conclude that the relative values of the kinetic parameters, some of which are functions of the f px , are applicable to nature.

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A few remarks on the kinetics of static grain growth in rocks

Cited by 259 publications

References 58 publications

Abrupt tectonics and rapid slab detachment with grain damage

Abrupt tectonics and rapid slab detachment with grain damage

Zebra pattern in rocks as a function of grain growth affected by second-phase particles

Influence of mineral fraction on the rheological properties of forsterite + enstatite during grain size sensitive creep: 3. Application of grain growth and flow laws on peridotite ultramylonite

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