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Stress sensitivity of high-temperature microstructures in ice, with potential applications to quartz

Platt, John P; Mitchell, TM; Prior, David J; Negrini, Marianne; Fan, Sheng; Jefferd, Mark; Winnard, Blaise; (2022) Stress sensitivity of high-temperature microstructures in ice, with potential applications to quartz. Journal of Structural Geology , 154 , Article 104487. 10.1016/j.jsg.2021.104487. Green open access

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Abstract

Quartz and ice both exhibit distinctive microstructures when deformed at low stress and high homologous temperature, known as grain-boundary migration (GBM) microstructures. These are difficult to reproduce experimentally in silicate minerals, and no correlation has been established between quantifiable aspects of the microstructure and deformational conditions. We carried out direct shear experiments to investigate the effect of stress and temperature (T) on GBM microstructures in ice, which is crystallographically analogous to quartz. Differential stress was 0.7–6.0 MPa, confining pressure 4–9 MPa, and T −3° to −25 °C. There is a clear transition at ∼ −12 °C from granular microstructures produced by rotation recrystallization at high stress and low T, to GBM microstructures at low stress and high T, accompanied by an increase in strength of the crystallographic preferred orientation (CPO). Samples with GBM microstructure show lobate grain-boundaries and “island grains” where several distinct and separate areas have the same crystallographic orientation, representing lobes of a single grain isolated on the cut surfaces. The size of lobes and island grains define an array with respect to stress with a slope of 0.9, similar to but offset from the slope of published stress/grain-size data. This suggests the possibility of determining paleostress from GBM microstructures in both ice and quartz.

Type: Article
Title: Stress sensitivity of high-temperature microstructures in ice, with potential applications to quartz
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.jsg.2021.104487
Publisher version: http://dx.doi.org/10.1016/j.jsg.2021.104487
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: CREEP, CRYSTALLOGRAPHIC PREFERRED ORIENTATIONS, DEFORMATION MECHANISMS, DYNAMIC RECRYSTALLIZATION, EBSD, Electron backscatter diffraction, Geology, Geosciences, Multidisciplinary, Ice, INSIGHTS, Microstructure, Migration recrystallization, Paleopiezometry, Physical Sciences, POLYCRYSTALLINE ICE, Quartz, RECRYSTALLIZED GRAIN-SIZE, Science & Technology, SIMPLE SHEAR, TEXTURE DEVELOPMENT
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery-pp.ucl.ac.uk/id/eprint/10191707
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