Dynamic Recrystallization Can Produce Porosity in Shear Zones

James Gilgannon, Thomas Poulet, Alfons Berger, Auke Barnhoorn, Marco Herwegh

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)
10 Downloads (Pure)

Abstract

Creep cavities are increasingly recognized as an important syn-kinematic feature of shear zones, but much about this porosity needs investigation. Largely, observations of creep cavities are restricted to very fine grained mature ultramylonites, and it is unclear when they developed during deformation. Specifically, a question that needs testing is should grain size reduction during deformation produce creep cavities? To this end, we have reanalyzed the microstructure of a large shear strain laboratory experiment that captures grain size change by dynamic recrystallization during mylonitization. We find that the experiment does contain creep cavities. Using a combination of scanning electron microscopy and spatial point statistics, we show that creep cavities emerge with, and because of, subgrain rotation recrystallization during ultramylonite formation. As dynamic recrystallization is ubiquitous in natural shear zones, this observation has important implications for the interpretation of concepts such as the Goetze criterion, paleopiezometery, and phase mixing.

Original languageEnglish
Article numbere2019GL086172
Number of pages10
JournalGeophysical Research Letters
Volume47
Issue number7
DOIs
Publication statusPublished - 2020

Keywords

  • Carrara marble
  • creep cavities
  • dynamic recrystallization
  • large shear strain
  • ultramylonite

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