• Strain rate dependent calcite microfabric evolution – An experiment carried out by nature

    • Anna Rogowitz
    • Department of Geodynamics and Sedimentology, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna
    • Bernhard Grasemann
    • Department of Geodynamics and Sedimentology, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna
    • Benjamin Huet
    • Department of Geodynamics and Sedimentology, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna
    • Gerlinde Habler
    • Department of Lithospheric Research, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna
  • A flanking structure developed along a secondary shear zone in calcite marbles, on Syros (Cyclades, Greece), provides a natural laboratory for directly studying the effects of strain rate variations on calcite deformation at identical pressure and temperature conditions. The presence and rotation of a fracture during progressive deformation caused extreme variations in finite strain and strain rate, forming a localized ductile shear zone that shows different microstructures and textures. Textures and the degree of intracrystalline deformation were measured by electron backscattered diffraction. Marbles from the host rocks and the shear zone, which deformed at various strain rates, display crystal-preferred orientation, suggesting that the calcite preferentially deformed by intracrystalline-plastic deformation. Increasing strain rate results in a switch from subgrain rotation to bulging recrystallization in the dislocation-creep regime. With increasing strain rate, we observe in fine-grained (3 μm) ultramylonitic zones a change in deformation regime from grain-size insensitive to grain-size sensitive. Paleowattmeter and the paleopiezometer suggest strain rates for the localized shear zone around 10 exp−10 s exp−1 and for the marble host rock around 10 exp−12 s exp−1. We conclude that varying natural strain rates can have a first-order effect on the microstructures and textures that developed under the same metamorphic conditions.

  • PDF

  • http://phaidra.univie.ac.at/o:406829

  • Article

  • Accepted Version

  • 2014

  • 69

  • 1-17

  • Elsevier BV

  • English

  • Embargoed access

  • 18.12.2016

  • I471-N19 – Austrian Science Fund (FWF)

  • 0191-8141

  • Calcite; Deformation mechanism; Recrystallization mechanism; Microfabric; Strain localization

  • Dewey Decimal Classification → Science → Earth sciences & geology → Earth sciences