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Post-deformational annealing at the subgrain scale: Temperature dependent behaviour revealed by in-situ heating experiments on deformed single crystal halite
Stockholm University, Faculty of Science, Department of Geological Sciences. (Petrotectonics)
Stockholm University, Faculty of Science, Department of Geological Sciences. (Petrotectonics)
2010 (English)In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 32, no 7, 982-996 p.Article in journal (Refereed) Published
Abstract [en]

The dynamics of substructures, which encompass all structures present at the subgrain-scale, were investigated by static, in-situ annealing experiments. Deformed, single crystal halite was annealed inside a scanning electron microscope at temperatures between 280-470 ºC. Electron backscatter diffraction maps provided detailed information about crystallographic orientation changes. Three temperature dependent regimes were distinguished based on boundary misorientation changes. In regime I (280-300 ºC) some low angle boundaries (LABs), i.e. with 1º-15º misorientation, increase in misorientation angle, while others decrease. In regime II (~300 ºC) all LABs undergo a decrease in misorientation angle. Regime III (>300 ºC) is defined by enhancement of the subgrain structure as remaining LABs increase and some undergo a rotation axis change. Throughout regimes I and II, new LABs develop, subdividing subgrains. LABs could be divided into four categories based on annealing behaviour, orientation and morphology. We suggest that these observations can be directly related to the mobility and activation temperature of climb of two dislocation groups introduced during deformation. Therefore, with in-depth investigation of a substructure with known deformation geometry, we can infer ratios of dislocation types and their post-deformation and post-annealing location. These can potentially be used to estimate the post-deformational annealing temperature in crystalline materials.

Place, publisher, year, edition, pages
2010. Vol. 32, no 7, 982-996 p.
Keyword [en]
halite, annealing, EBSD, substructure, in-situ
National Category
Geology
Research subject
Geology
Identifiers
URN: urn:nbn:se:su:diva-45682DOI: 10.1016/j.jsg.2010.06.006ISI: 000283687500009OAI: oai:DiVA.org:su-45682DiVA: diva2:369329
Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Fundamentals of substructure dynamics: In-situ experiments and numerical simulation
Open this publication in new window or tab >>Fundamentals of substructure dynamics: In-situ experiments and numerical simulation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Substructure dynamics incorporate all features occurring on a subgrain-scale. The substructure governs the rheology of a rock, which in turn determines how it will respond to different processes during tectonic changes. This project details an in-depth study of substructural dynamics during post-deformational annealing, using single-crystal halite as an analogue for silicate materials. The study combines three different techniques; in-situ annealing experiments conducted inside the scanning electron microscope and coupled with electron backscatter diffraction, 3D X-ray diffraction coupled with in-situ heating conducted at the European Radiation Synchrotron Facility and numerical simulation using the microstructural modelling platform Elle. The main outcome of the project is a significantly refined model for recovery at annealing temperatures below that of deformation preceding annealing. Behaviour is highly dependent on the temperature of annealing, particularly related to the activation temperature of climb and is also strongly reliant on short versus long range dislocation effects. Subgrain boundaries were categorised with regard to their behaviour during annealing, orientation and morphology and it was found that different types of boundaries have different behaviour and must be treated as such. Numerical simulation of the recovery process supported these findings, with much of the subgrain boundary behaviour reproduced with small variation to the mobilities on different rotation axes and increase of the size of the calculation area to imitate long-range dislocation effects. Dislocations were found to remain independent to much higher misorientation angles than previously thought, with simulation results indicating that change in boundary response occurs at ~7º for halite. Comparison of 2D experiments to 3D indicated that general boundary behaviour was similar within the volume and was not significantly influenced by effects from the free surface. Boundary migration, however, occurred more extensively in the 3D experiment. This difference is interpreted to be related to boundary drag on thermal grooves on the 2D experimental surface. While relative boundary mobilities will be similar, absolute values must therefore be treated with some care when using a 2D analysis.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University, 2010. 23 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 342
Keyword
halite, in-situ, X-ray diffraction, EBSD, annealing, substructure, modelling
National Category
Earth and Related Environmental Sciences
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-45811 (URN)978-91-7447-187-8 (ISBN)
Public defence
2010-12-20, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:30 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2010-11-28 Created: 2010-11-11 Last updated: 2010-12-03Bibliographically approved

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