A review of numerical modelling of the dynamics of microstructural development in rocks and ice: Past, present and future

Piazolo, Sandra; Bons, Paul D.; Griera, Albert; Llorens, Maria-Gema; Gomez‐Rivas, Enrique; Koehn, Daniel; Wheeler, John; Gardner, Robyn; Godinho, José R. A.; Evans, Lynn; Lebensohn, Ricardo A.; Jessell, Mark

doi:10.1016/j.jsg.2018.05.025

Cited by 30 publications

(22 citation statements)

References 126 publications

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“…The actual stress exponent in ice 1h may actually be closer to n=4 (Bons et al, 2018). The first tests show that raising n to 4 has little effect on the CPO, and in order to be coherent with previous ice CPO simulations (Llorens et al, 2016a, 2016bQi et al, 2018;Piazolo et al, 2019) all simulations presented here are carried out with the more commonly used n=3. Uniaxial shortening of a single crystal by glide along the non-basal planes only requires about 60 times higher stress than when the crystal can deform entirely by basal-plane glide (Duval et al, 1983).…”

Section: Methodssupporting

confidence: 60%

“…Bons et al, 2008). ELLE has been successfully used for the simulation of a variety of studies of rock microstructure evolution during deformation and metamorphism (see Piazolo et al, 2019). The coupling of the full-field VPFTT code and ELLE allows simulating deformation of a polycrystalline aggregate by dislocation glide up to high strains (>10) as often found in nature in ice and rocks.…”

Section: Flow Regime Transitions In Polar Ice Sheets 110mentioning

confidence: 99%

“…Numerical modelling provides an alternative approach to overcome these limitations because it allows a continuous analysis of multiple deformation scenarios with a wide variety of deformation 85 kinematics and environmental parameters. Moreover, numerical simulations of polycrystalline ice and their comparison with experimental and natural data provide useful insights into the study of the CPO development, as they allow visualizing and quantifying the microstructural evolution up to high strain (Montagnat et al, 2014b;Llorens et al, 2016aLlorens et al, 2016bPiazolo et al, 2019). However, as in the case of laboratory experiments, 90 most numerical studies to date have focused on systems starting with an initially random CPO to which a single deformation event is applied.…”

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confidence: 99%

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Can changes in ice-sheet flow be inferred from crystallographic preferred orientations?

Llorens

Griera²,

Bons

et al. 2021

Preprint

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Abstract. Creep due to ice flow is generally thought to be the main cause for the formation of crystallographic preferred orientations (CPOs) in polycrystalline anisotropic ice. However, linking the development of CPOs to the ice flow history requires a proper understanding of the ice aggregate's microstructural response to flow transitions. In this contribution the influence of ice deformation history on the CPO development is investigated by means of full-field numerical simulations at the microscale. We simulate the CPO evolution of polycrystalline ice under combinations of two consecutive deformation events up to high strain, using the code VPFFT/ELLE. A volume of ice is first deformed under co-axial boundary conditions, which results in a CPO. The sample is then subjected to different boundary conditions (co-axial or non-coaxial) in order to observe how the deformation regime switch impacts on the CPO. The model results indicate that the second flow event tends to destroy the first, inherited fabric, with a range of transitional fabrics. However, the transition is slow when crystallographic axes are critically oriented with respect to the second imposed regime. Therefore, interpretations of past deformation events from observed CPOs must be carried out with caution, particularly, in areas with complex deformation histories.

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Section: Methodssupporting

confidence: 60%

Section: Flow Regime Transitions In Polar Ice Sheets 110mentioning

confidence: 99%

mentioning

confidence: 99%

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Can changes in ice-sheet flow be inferred from crystallographic preferred orientations?

Llorens

Griera²,

Bons

et al. 2021

Preprint

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“…The models use the Elle open source numerical simulation platform (Bons et al, 2008;Piazolo et al, 2018), as developed in Gardner et al (2017). The models have a 2-D structure with two layers of information.…”

Section: Elle Modelmentioning

confidence: 99%

Ductile Deformation Without Localization: Insights From Numerical Modeling

Gardner

Piazolo

Daczko

et al. 2019

Geochem Geophys Geosyst

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Strain is easily localized in a polyphase rock, especially if the rock undergoes syntectonic weakening processes. However, there is ample field evidence for distributed, rather than localized, deformation at the outcrop to hundreds of square kilometer scale. In these areas, distributed strain is evidenced by the presence of continuous foliations and a lack of distinct high-strain zones. Here, we use numerical modeling of viscous deformation to investigate the conditions that allow distributed rather than localized deformation. We identify three strain localization regimes for a system with rheologically strong and weak phases with or without stress-induced weakening. Regime I is characterized by distributed strain. It forms where either deformation-induced interconnection of the weak phase is not possible or the initial weak phase area is intermediate to high (i.e., >~40-60% of total depending on weak phase geometry). Their resultant bulk strength is either strong or weak, respectively. Regime II is characterized by variably distributed areas of strain localization and develops if the initial proportion of weak phases is intermediate (i.e., 40-60% weak phase depending on geometry) and syntectonic weakening causes an increase (up to~12%) of weak phase proportion. Regime III exhibits significant strain localization and only develops if the initial proportion of weak phases is relatively low (<20%) and syntectonic weakening increases the proportion of weak phases by over~12%. Here, high-strain zones readily form irrespective of the initial distribution of rheologically weak and hard phases, and bulk strength is intermediate. Plain Language SummaryOver many years, scientists have concentrated on the question of how deformation is localized in zones of high strain. Hence, areas without these zones, where deformation is distributed, have not been given much attention. This is because it has often been assumed that these areas were insignificant in terms of how deformation is accommodated. In this research we take a different approach and ask the question: "Under what conditions does deformation remain distributed rather than become localized?" To find out, we have run a series of computer simulations testing scenarios that allow or do not allow distributed deformation to occur. If there is a mix of weak and strong phases, for example, two different types of rocks or minerals (as typical in the Earth), then there are two main requirements to form areas of distributed strain: (i) the proportion of weak phases is either high or low (i.e., not intermediate) and (ii) there is no way the strong phase can become weakened. Our results are important for the interpretation of areas that show distributed strain and their significance in the overall deformation of the Earth's crust and mantle.

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“…We use the Viscoplastic Full-Field Transform (VPFFT; Lebensohn and Rollett, 2020) crystal plasticity code coupled with the modelling platform ELLE (http://www.elle.ws; Piazolo et al, 2019) to simulate the deformation of intrinsically anisotropic ice 1h with an initial single maximum CPO in dextral simple shear up to very high strains. The VPFFT-approach simulates deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses.…”

mentioning

confidence: 99%

Deformation structures resulting from anisotropy during high-strain deformation of ice 1h with initial CPO

Riese¹,

Bons²,

Gomez‐Rivas

et al. 2021

Preprint

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Ice 1h shows a strong viscoplastic anisotropy, as the resistance to activate dislocation glide on basal planes is at least one order of magnitude smaller than on the other slip planes. During flow the viscoplastic anisotropy leads to the development of a crystallographic preferred orientation (CPO). The anisotropic behaviour of flowing ice can lead to strain localisation. Only when the ice is layered (e.g. due to cloudy bands) it may be possible to identify localisation structures, as ice otherwise has no readily recognisable strain markers.We use the Viscoplastic Full-Field Transform (VPFFT; Lebensohn and Rollett, 2020) crystal plasticity code coupled with the modelling platform ELLE (http://www.elle.ws; Piazolo et al., 2019) to simulate the deformation of intrinsically anisotropic ice 1h with an initial single maximum CPO in dextral simple shear up to very high strains. The VPFFT-approach simulates deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses. We use an anisotropy similar to that of ice 1h, systematically vary the orientation of the initial CPO, and use passive markers/layers to visualise deformation structures.The localisation behaviour strongly depends on the initial CPO, but reaches a consistent steady state after very high shear strains of about 30. The fabric and stress evolution reach a steady-state situation as well. The orientation of the CPO controls the style of deformation, which varies from (1) synthetic shear zones with a stable shear-direction parallel orientation and that widen with ongoing strain to unstable, (2) rotating antithetic shear bands, (3) initial formation of antithetic shear bands and subsequent development of synthetic shear bands and (4) distributed localisation. Furthermore, evolving visual structures depend on the presence and orientation of a visual layering in the material. However, at very high strains, the material is almost always strongly mixed and any original layering would be destroyed.Our results highlight the challenge to identify strain localisation in ice, yet they can help the ice community to identify and interpret deformation structures in large ice masses (e.g. the Greenland ice sheet). As strain localisation in anisotropic materials behaves scale independent (de Riese et al., 2019), large-scale equivalents may occur of the observed small-scale structures (Jansen et al., 2016).References:de Riese, T., Evans, L., Gomez-Rivas, E., Griera, A., Lebensohn, R.A., Llorens, M.G., Ran, H., Sachau, T., Weikusat, I., Bons, P.D. 2019. Shear localisation in anisotropic, non-linear viscous materials that develop a CPO: A numerical study. Journal of Structural Geology, 124, 81-90.Jansen, D., Llorens, M.-G, Westhoff, J., Steinbach, F., Kipfstuhl, S., Bons, P.D., Griera, A., Weikusat, I. 2016. Small-scale disturbances in the stratigraphy of the NEEM ice core: observations and numerical model simulations. The Cryosphere 10, 359-370.Lebensohn, R.A., Rollett, A.D. 2020. Spectral methods for full-field micromechanical modelling of polycrystalline materials.&#160;Computational Materials Science,&#160;173, 109336.Piazolo, S., Bons, P.D., Griera, A., Llorens, M.G., Gomez-Rivas, E., Koehn, D., ... Jessell, M.W. 2019. A review of numerical modelling of the dynamics of microstructural development in rocks and ice: Past, present and future. Journal of Structural Geology, 125, 111-123.

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A review of numerical modelling of the dynamics of microstructural development in rocks and ice: Past, present and future

Cited by 30 publications

References 126 publications

Can changes in ice-sheet flow be inferred from crystallographic preferred orientations?

Can changes in ice-sheet flow be inferred from crystallographic preferred orientations?

Ductile Deformation Without Localization: Insights From Numerical Modeling

Deformation structures resulting from anisotropy during high-strain deformation of ice 1h with initial CPO

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