The most frequent interfaces in olivine aggregates: the GBCD and its importance for grain boundary related processes

Marquardt, Katharina; Rohrer, Gregory S.; Morales, Luiz F. G.; Rybacki, E.; Marquardt, Hauke; Bo, Lin

doi:10.1007/s00410-015-1193-9

Cited by 29 publications

(40 citation statements)

References 96 publications

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“…The distribution of grain boundary misorientation angles (Figure 8) showing a peak at 90° is typical for a uniform distribution for orthorhombic crystal symmetry (Morawiec, 2004). The secondary peak at 10° matches well with observations from Marquardt et al (2015), who investigated the grain boundary character distribution of undeformed synthetic and natural polycrystalline olivine.…”

Section: Deformation Mechanisms and Microstructuresupporting

confidence: 85%

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Thieme

Demouchy

Mainprice

et al. 2018

Physics of the Earth and Planetary Interiors

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Section: Deformation Mechanisms and Microstructuresupporting

confidence: 85%

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Thieme

Demouchy

Mainprice

et al. 2018

Physics of the Earth and Planetary Interiors

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“…57E-04 ±4E-6; b' = 1.113 ±0.006; c' = 3.92E-03 ±9E-5; d' = -4.082 ±0.14. In this range of melt fraction with a lower degree of connectivity, if m = 1.37, then the preexponential factor A = 2.9 log units, being a value too high for the conductivity of basaltic melt. Hence, there must be other phase more conductive than olivine to get m = 1.37, such as, for instance, grain boundary effects that become more and more significant at lower melt fractions (Marquardt et al, 2015). Both models reproduce very closely the experimental results (see Fig.…”

Section: Model Of the Ec Of Partially-molten Olivine Aggregatesupporting

confidence: 63%

Experimental determination of melt interconnectivity and electrical conductivity in the upper mantle

Laumonier

Farla

Frost

et al. 2017

Earth and Planetary Science Letters

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International audienceThe presence of a small fraction of basaltic melt is a potential explanation for mantle electrical conductivity anomalies detected near the top of the oceanic asthenosphere. The interpretation of magnetotelluric profiles in terms of the nature and proportion of melt, however, relies on mathematical models that have not been experimentally tested at realistically low melt fractions (<0.01). In order to address this, we have performed in situ electrical conductivity measurements on partially molten olivine aggregates. The obtained data suggest that the bulk conductivity follows the conventional Archie's law with the melt fraction exponents of 0.75 and 1.37 at melt fractions greater and smaller than 0.5 vol.% respectively at 1350 °C. Our results imply multiple conducting phases in melt-bearing olivine aggregate and a connectedness threshold at ∼0.5 vol.% of melt. The model predicts that the conductive oceanic upper asthenosphere contains 0.5 to 1 vol.% of melt, which is consistent with the durable presence of melt at depths over millions years while the oceanic plates spread apart at the mid-ocean ridge. Beneath ridges a minimum permeability may allow mid-ocean ridge basalts to rise out of the mantle, where our model indicates that melt is present in proportions of up to 4 vol.%

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“…Direct analysis of grain boundary planes such as that used in Marquardt et al . [], who found preferential crystallographic grain boundary planes in polycrystalline materials, provides more details on the appearance of such boundaries.…”

Section: Discussionmentioning

confidence: 99%

“…From the appearance of grain shapes in the SEM images, we estimated the presence of low-index plane boundaries that we consider to correspond to low-viscosity boundaries. Direct analysis of grain boundary planes such as that used in Marquardt et al [2015], who found preferential crystallographic grain boundary planes in polycrystalline materials, provides more details on the appearance of such boundaries.…”

Section: Diffusion Creep (Superplastic) Earth Hypothesismentioning

confidence: 99%

Grain‐ to multiple‐grain‐scale deformation processes during diffusion creep of forsterite + diopside aggregate: 2. Grain boundary sliding‐induced grain rotation and its role in crystallographic preferred orientation in rocks

Maruyama

Hiraga

2017

JGR Solid Earth

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Polycrystalline samples composed of either tabular or equiaxed forsterite grains +diopside (5 and 20 vol %) were deformed with a grid etched onto the lateral surface. In Part 1 of this study, we identified grain boundary sliding (GBS) and rigid body‐like grain rotation during deformation by diffusion creep where samples with tabular forsterite grains were shown to develop low‐index plane grain boundaries that result in crystallographic preferred orientation (CPO). Here we examine how grain rotation depends on the sample strain, grain size, phases, grain shapes, and orientations relative to the compression axis and long axes of tabular forsterite grains. Based on these results, we model grain rotation due to GBS that occurs preferentially along low‐index plane boundaries. The model reproduces all of the characteristics of grain rotation and together with the observed grain rotation rates in tabular and equiaxed grain samples, we estimate that low‐index plane boundaries have a lower viscosity by a factor of ~3 relative to general grain boundaries, which results in the development of CPO during diffusion creep. The observed constant rotation rate of ~0.4 (radian/strain) in equiaxed‐grain samples and in tabular‐grain samples deformed to a strain of >0.5 is considered to be a minimum and further, a material‐independent rotation rate during diffusion creep, indicating grain rotation as a primary microprocess during diffusion creep. We discuss the possible consequences of GBS‐induced grain rotation and CPO development in rock microstructure and the seismic properties of the Earth's mantle.

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The most frequent interfaces in olivine aggregates: the GBCD and its importance for grain boundary related processes

Cited by 29 publications

References 96 publications

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Experimental determination of melt interconnectivity and electrical conductivity in the upper mantle

Grain‐ to multiple‐grain‐scale deformation processes during diffusion creep of forsterite + diopside aggregate: 2. Grain boundary sliding‐induced grain rotation and its role in crystallographic preferred orientation in rocks

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The most frequent interfaces in olivine aggregates: the GBCD and its importance for grain boundary related processes

Cited by 29 publications

References 96 publications

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Experimental determination of melt interconnectivity and electrical conductivity in the upper mantle

Grain‐ to multiple‐grain‐scale deformation processes during diffusion creep of forsterite + diopside aggregate: 2. Grain boundary sliding‐induced grain rotation and its role in crystallographic preferred orientation in rocks

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Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C