Journal
TECTONOPHYSICS
Volume 680, Issue -, Pages 129-139Publisher
ELSEVIER
DOI: 10.1016/j.tecto.2016.05.022
Keywords
Quartz; CPO; Mylonite; Deformation mechanisms; Recrystallization
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Funding
- NSF [EAR-1141795]
- Lenfest Sabbatical Fellowship from Washington and Lee University
- Lenfest Summer Research Grant from Washington and Lee University
- Division Of Earth Sciences
- Directorate For Geosciences [1141795] Funding Source: National Science Foundation
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We present microstructural and crystallographic preferred orientation (CPO) data on quartz deformed in the middle crust to explore the interaction and feedback between dynamic recrystallization, deformation processes, and CPO evolution. The sample investigated here is a moderately deformed quartz-rich mylonite from the Blue Ridge in Virginia. We have created high-resolution crystallographic orientation maps using electron bacicscatter diffraction (EBSD) of 51 isolated quartz porphyroclasts with recrystallized grain fractions ranging from 10 to 100%. Recrystallized grains are internally undeformed and display crystallographic orientations dispersed around the orientation of the associated parent porphyroclast. We document a systematic decrease in fabric intensity with recrystallization, suggesting that progressive deformation of the recrystallized domains involves processes that can weaken a pre-existing CPO. Relationships between recrystallization fraction and shear strain suggest that complete microstructural re-equilibration requires strains in excess of gamma = 5. Variation in the degree of re crystallization implies that strain was accumulated heterogeneously, and that a steady-state microstructure and rheology were not achieved. (C) 2016 Elsevier B.V. All rights reserved.
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