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| Titel |
Strain rate dependent activation of slip systems in calcite marbles from Syros (Cyclades, Greece) |
| VerfasserIn |
Anna Rogowitz, Bernhard Grasemann, Luiz F. G. Morales, Benjamin Huet, Joseph C. White |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148095
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| Publikation (Nr.) |
 EGU/EGU2017-12324.pdf |
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| Zusammenfassung |
| The activation of certain slip systems in calcite has been experimentally proven to be highly
temperature dependent, but also the strain rate plays an important role on the activation
of the dominant slip system. In this study, observations from a flanking structure
(i.e. shear zone) that developed under lower greenschist-facies conditions, in an
almost pure calcite marble (Syros Island, Greece) are presented. The shear zone is
characterized by a strain gradient from the slightly deformed tips (γ ∼ 50) to the highly
strained centre (γ up to 1000) while the host rock is moderately deformed (γ ∼ 3).
During the shear zone development, the strain gradient coincided with a strain rate
gradient with strain rate varying from 10−13 to 10−9 s−1. The studied outcrop thus
represents the final state of a natural experiment and gives us a great opportunity to get
natural constraints on strain rate dependent mechanical behaviour in a calcite marble.
Detailed microstructural analyses have been performed via optical microscopy,
electron microscopy, electron backscatter diffraction mapping and transmission
electron microscopy, on samples from the highly strained shear zone and the host
rock. The analyses show that the calcite microfabric varies depending on position
within the shear zone, indicating activation of different deformation, recrystallization
mechanisms and slip systems at different strain rates. Up to strain rates of ∼10−10
s−1 the marble deformed exclusively within the dislocation creep field, showing a
change in recrystallization mechanism and dominant active slip system. While
the marble preferentially recrystallized by grain boundary migration at relatively
low strain rates (∼10−13 s−1), subgrain rotation recrystallization seems to be the
dominant mechanism at higher strain rates (∼10−12 to 10−10 s−1). At higher strain
rates (∼10−9 s−1), the recrystallization mechanism is bulging, resulting in the
development of an extremely fine grained ultramylonite (average grain size ∼3 μm)
accompanied by a switch in deformation mechanism from dislocation creep to a
combined deformation by grain boundary sliding and dislocation activity. Constraints
on dominant active slip system depending on deformation strain rate have been
made by a combination of misorientation analyses and viscoplastic self-consistent
modelling. |
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