LPO development in fine-grained dolomite shear zones
Abstract
Formation of a weak lattice preferred orientation is common within localized zones of experimentally and naturally deformed dolomite. We have analyzed LPOs in two experimental and two natural fine-grained dolomite shear zones. The two experimentally deformed dolomites at 900 °C and laboratory strain rates include: 1) a coarse-grained dolomite that underwent grain size reduction and localization, and 2) a fine-grained dolomite that did not undergo grain size reduction. The two naturally deformed fine-grained dolomite shear zones include: 1) the Pioneer Landing thrust and 2) the Town Knobs thrust of the southern Appalachians, deformed at 300 °C and 240 °C, respectively, at tectonic strain rates. Microstructures outside of the shear zones include subgrains and recrystallized grains along grain- and twin- boundaries which indicate the primary mechanism for grain size reduction was through dislocation processes. Microstructures in the experimental fine-grained shear zones include a weak c-axis lattice preferred orientation, some subgrains and many four-grain junctions. Microstructures in the natural fine-grained shear zones include slightly stronger lattice preferred orientations than in the experimental shear zones, subgrains, and fewer four-grain junctions. The occurrence of these structures indicates the combined operation of dislocation creep, diffusion creep, and grain boundary sliding contribute to the formation of a weak c-axis orientation within fine-grained dolomite.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMMR24A..06W
- Keywords:
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- 3625 Petrography;
- microstructures;
- and textures;
- MINERALOGY AND PETROLOGYDE: 8004 Dynamics and mechanics of faulting;
- STRUCTURAL GEOLOGYDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8160 Rheology: general;
- TECTONOPHYSICS