The application of an automated fabric analyzer system to the textural evolution of folded ice layers in shear zones
Abstract:Layered ice has been used to investigate the initiation of fabrics in shear zones where there is preservation of a refolded layering.The fabrics were measured using an apparatus that acquires pixel-based images that illustrate the variation of c-axis orientation within and between grains. In the centre of the shear zones there is dynamic recrystallization with the production of an asymmetric two-maxima fabric. The way dynamic recrystallization modifies the inherited folds and microstructure suggests that there is little effect of inheritance from a precursor grain microstructure or fabric. No obvious evidence has been found for the occurrence of sub-grains, which implies that the role of sub-grain rotation is minimal or is obliterated by the recrystallization process. The final c-axis pattern is asymmetric with respect to the direction of shortening, with a strong maximum at ~5° to the pole of the shear zone, and a sense of asymmetry in the direction of the shear, and a secondary maximum inclined at ~45° to the plane of shearing. Distinct sets of nearest-neighbour c-axis distributions, namely, intermediate-angle (10-25°), high-angle (50-65°) and very high-angle (120-150°), suggest there may be special grain-boundary relationships.
Document Type: Research Article
Publication date: 2003-06-01
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