Modeling the effect of subgrain rotation recrystallization on the evolution of olivine crystal preferred orientations in simple shear

Signorelli, Javier; Tommasi, Andréa

doi:10.1016/j.epsl.2015.08.018

Cited by 29 publications

(27 citation statements)

References 56 publications

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“…Olivine CPOs from other peridotite localities (e.g., Ben Ismaïl & Mainprice, 1998;Bernard et al, 2019) also exhibit similar texture strengths to our samples, though strain is unquantified in these examples. The overprediction of texture strength by the Hansen, Conrad, et al (2016) model is observed in other texture models (e.g., VPSC in Signorelli & Tommasi, 2015). The differences between natural samples and experimental samples in this regard remains unclear but may reflect the multiphase lithology of the natural samples.…”

Section: The Influence Of a Preexisting Cpomentioning

confidence: 83%

Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution

2019

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Seismic anisotropy arises in the upper mantle due to the alignment of olivine crystal lattices and is often used to interpret mantle flow direction. Experiments on the evolution of olivine crystal‐preferred orientation (CPO) have found that the texture that develops is dependent on many factors, including water content, differential stress, preexisting CPO, and deformation kinematics. To evaluate the role of these factors in naturally deformed samples, we present microstructural transects across three shear zones in the Josephine Peridotite. Samples from these shear zones exhibit a mixture of A‐type textures, which have been associated with dry conditions and primary activation of the olivine [100](010) slip system, and of E‐type textures, which have been associated with wetter conditions and primary activation of the [100](001) slip system. CPOs with characteristics of both A‐type and E‐type textures are also present. CPO type does not evolve systematically as a function of either strain or water content. We used a micromechanical model to evaluate the roles of preexisting texture and kinematics on olivine CPO evolution. We find that the preexisting texture controls CPO evolution at strains up to 5 during simple shear. Kinematics involving a combination of simple shear and pure shear can explain the olivine CPOs at higher strain. Hence, preexisting CPOs and deformation kinematics should be considered in the interpretation of CPOs measured in naturally deformed rocks and of large‐scale patterns in upper‐mantle seismic anisotropy.

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Section: The Influence Of a Preexisting Cpomentioning

confidence: 83%

Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution

2019

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“…The rates of this change in orientation are well reproduced by all except the VPSC model, which exhibits significantly slower evolution than the other models in torsion. This behavior is likely due to the absence of an explicit scheme for simulating dynamic recrystallization in our VPSC model, as has been attempted in some recent models [ Signorelli and Tommasi , ]. The VPSC simulations also begin to exhibit some numerical instability at shear strains of ~5.…”

Section: Discussionmentioning

confidence: 99%

Viscous anisotropy of textured olivine aggregates: 2. Micromechanical model

et al. 2016

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The significant viscous anisotropy that results from crystallographic alignment (texture) of olivine grains in deformed upper mantle rocks strongly influences a large variety of geodynamic processes. Our ability to explore the effects of anisotropic viscosity in simulations of these processes requires a mechanical model that can predict the magnitude of anisotropy and its evolution. Unfortunately, existing models of olivine textural evolution and viscous anisotropy are calibrated for relatively small deformations and simple strain paths, making them less general than desired for many large‐scale geodynamic scenarios. Here we develop a new set of micromechanical models to describe the mechanical behavior and textural evolution of olivine through a large range of strains and complex strain histories. For the mechanical behavior, we explore two extreme scenarios, one in which each grain experiences the same stress tensor (Sachs model) and one in which each grain undergoes a strain rate as close as possible to the macroscopic strain rate (pseudo‐Taylor model). For the textural evolution, we develop a new model in which the director method is used to control the rate of grain rotation and the available slip systems in olivine are used to control the axis of rotation. Only recently has enough laboratory data on the deformation of olivine become available to calibrate these models. We use these new data to conduct inversions for the best parameters to characterize both the mechanical and textural evolution models. These inversions demonstrate that the calibrated pseudo‐Taylor model best reproduces the mechanical observations. Additionally, the pseudo‐Taylor textural evolution model can reasonably reproduce the observed texture strength, shape, and orientation after large and complex deformations. A quantitative comparison between our calibrated models and previously published models reveals that our new models excel in predicting the magnitude of viscous anisotropy and the details of the textural evolution. In addition, we demonstrate that the mechanical and textural evolution models can be coupled and used to reproduce mechanical evolution during large‐strain torsion tests. This set of models therefore provides a new geodynamic tool for incorporating viscous anisotropy into large‐scale numerical simulations.

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“…Future versions of texture models may benefit from subroutines that progressively randomize texture when grain-size is reduced below a certain threshold and indeed there have been a number of recent advances in the simulation of dynamic recrystallization processes (e.g., the CDRX-VPSC model of Signorelli and Tommasi [2015]. Validation of new models will benefit from additional comparisons between existing models, such as the work by Castelnau et al [2008], and comparisons with experimental results such as Boneh and Skemer [2014], applying the more stringent requirement that models must be able to reproduce a full spectrum of deformation histories.…”

Section: The Role Of Dynamic Recrystallization and Secondary Deformatmentioning

confidence: 99%

Modeling olivine CPO evolution with complex deformation histories: Implications for the interpretation of seismic anisotropy in the mantle

Boneh

Morales

Kaminski

et al. 2015

Geochem Geophys Geosyst

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Relating seismic anisotropy to mantle flow requires detailed understanding of the development and evolution of olivine crystallographic preferred orientation (CPO). Recent experimental and field studies have shown that olivine CPO evolution depends strongly on the integrated deformation history, which may lead to differences in how the corresponding seismic anisotropy should be interpreted. In this study, two widely used numerical models for CPO evolution-D-Rex and VPSC-are evaluated to further examine the effect of deformation history on olivine texture and seismic anisotropy. Building on previous experimental work, models are initiated with several different CPOs to simulate unique deformation histories. Significantly, models initiated with a preexisting CPO evolve differently than the CPOs generated without preexisting texture. Moreover, the CPO in each model evolves differently as a function of strain. Numerical simulations are compared to laboratory experiments by Boneh and Skemer (2014). In general, the D-Rex and VPSC models are able to reproduce the experimentally observed CPOs, although the models significantly over-estimate the strength of the CPO and in some instances produce different CPO from what is observed experimentally. Based on comparison with experiments, recommended parameters for D-Rex are: M* 5 10, k* 5 5, and v 5 0.3, and for VPSC: a 5 10-100. Numerical modeling confirms that CPO evolution in olivine is highly sensitive to the details of the initial CPO, even at strains greater than 2. These observations imply that there is a long transient interval of CPO realignment which must be considered carefully in the modeling or interpretation of seismic anisotropy in complex tectonic settings.

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Modeling the effect of subgrain rotation recrystallization on the evolution of olivine crystal preferred orientations in simple shear

Cited by 29 publications

References 56 publications

Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution

Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution

Viscous anisotropy of textured olivine aggregates: 2. Micromechanical model

Modeling olivine CPO evolution with complex deformation histories: Implications for the interpretation of seismic anisotropy in the mantle

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