The misorientation index: Development of a new method for calculating the strength of lattice-preferred orientation

Skemer, Philip; Katayama, Ikuo; Jiang, Zhenting; Karato, Shun‐ichiro

doi:10.1016/j.tecto.2005.08.023

Cited by 341 publications

(304 citation statements)

References 12 publications

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“…These values are small compared to those of some olivinerich rocks deformed to large strain naturally [e.g., Warren et al, 2008] and experimentally [e.g., Skemer et al, 2005], consistent with the relatively small magnitude of strain in our experiments. Skemer et al [2005] observed M indices of 0.01 for starting material and 0.17 after a shear strain of 60%. This shear strain converts to an effective strain of 35%, which is a factor of about 2 larger than the largest strains in our experiments.…”

Section: Microstructural Resultssupporting

confidence: 89%

Grain boundary sliding in San Carlos olivine: Flow law parameters and crystallographic-preferred orientation

2011

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[1] We performed triaxial compressive creep experiments on aggregates of San Carlos olivine to develop a flow law and to examine microstructural development in the dislocationaccommodated grain boundary sliding regime (GBS). Each experiment included load and temperature steps to determine both the stress exponent and the activation energy. Grain boundary maps, created with electron backscatter diffraction data, were used to quantify grain size distributions for each sample. Inversion of the resulting data produced the following flow law for GBS: _ " GBS = 10 4.8 ± 0.8 (s (010)[100] slip system contributes significantly to deformation. We propose that these experimental results are best modeled by a deformation mechanism in which strain is accomplished primarily through grain boundary sliding accommodated by the motion of dislocations. Extrapolation of our flow laws to mantle conditions suggests that GBS is likely to be the dominant deformation mechanism in both lithospheric shear zones and asthenospheric flow, and therefore strong upper mantle seismic anisotropy can not be attributed solely to the dominance of dislocation creep.

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Section: Microstructural Resultssupporting

confidence: 89%

Grain boundary sliding in San Carlos olivine: Flow law parameters and crystallographic-preferred orientation

2011

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“…Another CPO strength characteristic based on the misorientation angle distribution, introduced by Skemer et al (2005), is called the M-index. The method is based on the difference between the theoretical uniform distribution and the measured uncorrelated misorientation angle distributions for a given crystal symmetry class.…”

Section: Strengthmentioning

confidence: 99%

“…The M-index only uses the marginal angle distribution of the misorientation distribution function (MDF), as any misorientation can be decomposed into a rotation axis and angle and only the angle is used to calculated the M-index. As the discrete approach has already been described by Skemer et al (2005), we illustrate how to calculate the M-index using the continuous functions with MTEX. The following four steps are required:…”

Section: Strengthmentioning

confidence: 99%

Descriptive tools for the analysis of texture projects with large datasets using `MTEX` : strength, symmetry and components

et al. 2014

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This paper presents the background for the calculation of various numbers that can be used to characterize crystal-preferred orientation (CPO), also known as texture in materials science, for large datasets using the combined scripting possibilities of MTEX and MatLab w . The paper is focused on three aspects in particular: the strength of CPO represented by orientation and misorientation distribution functions (ODFs, MDFs) or pole figures (PFs); symmetry of PFs and components of ODFs; and elastic tensors. The traditional measurements of texture strength of ODFs, MDFs and PFs are integral measurements of the distribution squared. The M-index is a partial measure of the MDF as the difference between uniform and measured misorientation angles. In addition there other parameters based on eigen analysis, but there are restrictions on their use. Eigen analysis does provide some shape factors for the distributions. The maxima of an ODF provides information on the modes. MTEX provides an estimate of the lower bound uniform fraction of an ODF. Finally, we illustrate the decomposition of arbitrary elastic tensor into symmetry components as an example of components in anisotropic physical properties. Ten examples scripts and their output are provided in the appendix.

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“…To quantify the strength of olivine crystallographic preferred orientation (CPO) we used the J index (Bunge, 1982) and M index (Skemer et al, 2005).…”

Section: Analysis Of Crystallographic Preferred Orientationsmentioning

confidence: 99%

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

et al. 2017

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Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.

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The misorientation index: Development of a new method for calculating the strength of lattice-preferred orientation

Cited by 341 publications

References 12 publications

Grain boundary sliding in San Carlos olivine: Flow law parameters and crystallographic-preferred orientation

Grain boundary sliding in San Carlos olivine: Flow law parameters and crystallographic-preferred orientation

Descriptive tools for the analysis of texture projects with large datasets using `MTEX` : strength, symmetry and components

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

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The misorientation index: Development of a new method for calculating the strength of lattice-preferred orientation

Cited by 341 publications

References 12 publications

Grain boundary sliding in San Carlos olivine: Flow law parameters and crystallographic-preferred orientation

Grain boundary sliding in San Carlos olivine: Flow law parameters and crystallographic-preferred orientation

Descriptive tools for the analysis of texture projects with large datasets using MTEX : strength, symmetry and components

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

Contact Info

Product

Resources

About

Descriptive tools for the analysis of texture projects with large datasets using `MTEX` : strength, symmetry and components