Crystallographic preferred orientations of ice deformed in direct-shear experiments at low temperatures
Qi, Chao (Chinese Academy of Sciences. Institute of Geology and Geophysics)
Prior, David (University of Otago. Department of Geology)
Craw, Lisa (University of Otago. Department of Geology)
Fan, Sheng (University of Otago. Department of Geology)
Llorens, Maria-Gema (Universitat Autònoma de Barcelona. Departament de Geologia)
Griera Artigas, Albert (Universitat Autònoma de Barcelona. Departament de Geologia)
Negrini, Marianne (University of Otago. Department of Geology)
Bons, Paul D. (Eberhard Karls University of Tübingen. Department of Geosciences)
Goldsby, David L. (University of Pennsylvania. Department of Earth and Environmental Science)

Data:	2019
Resum:	Synthetic polycrystalline ice was sheared at temperatures of-5,-20 and-30 °C, to different shear strains, up to γ = 2. 6, equivalent to a maximum stretch of 2. 94 (final line length is 2. 94 times the original length). Cryo-electron backscatter diffraction (EBSD) analysis shows that basal intracrystalline slip planes become preferentially oriented parallel to the shear plane in all experiments, with a primary cluster of crystal c axes (the c axis is perpendicular to the basal plane) perpendicular to the shear plane. In all except the two highest-strain experiments at-30 °C, a secondary cluster of c axes is observed, at an angle to the primary cluster. With increasing strain, the primary c-axis cluster strengthens. With increasing temperature, both clusters strengthen. In the-5 °C experiments, the angle between the two clusters reduces with strain. The c-axis clusters are elongated perpendicular to the shear direction. This elongation increases with increasing shear strain and with decreasing temperature. Highly curved grain boundaries are more prevalent in samples sheared at higher temperatures. At each temperature, the proportion of curved boundaries decreases with increasing shear strain. Subgrains are observed in all samples. Microstructural interpretations and comparisons of the data from experimentally sheared samples with numerical models suggest that the observed crystallographic orientation patterns result from a balance of the rates of lattice rotation (during dislocation creep) and growth of grains by strain-induced grain boundary migration (GBM). GBM is faster at higher temperatures and becomes less important as shear strain increases. These observations and interpretations provide a hypothesis to be tested in further experiments and using numerical models, with the ultimate goal of aiding the interpretation of crystallographic preferred orientations in naturally deformed ice.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Publicat a:	Cryosphere, Vol. 13, Issue 1 (February 2019) , p. 351-371, ISSN 1994-0424

DOI: 10.5194/tc-13-351-2019

21 p, 10.8 MB

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