skip to main content

DOE PAGESDOE PAGES

Title: Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the Y Z plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains frommore » a grain-size-insensitive to a grain-size-sensitive rheology.« less
Authors:
ORCiD logo ; ORCiD logo ; ORCiD logo ; ;
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Published Article
Journal Name:
Solid Earth (online)
Additional Journal Information:
Journal Name: Solid Earth (online) Journal Volume: 8 Journal Issue: 6; Journal ID: ISSN 1869-9529
Publisher:
Copernicus GmbH
Sponsoring Org:
USDOE
Country of Publication:
Germany
Language:
English
OSTI Identifier:
1459997

Gilgannon, James, Fusseis, Florian, Menegon, Luca, Regenauer-Lieb, Klaus, and Buckman, Jim. Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing. Germany: N. p., Web. doi:10.5194/se-8-1193-2017.
Gilgannon, James, Fusseis, Florian, Menegon, Luca, Regenauer-Lieb, Klaus, & Buckman, Jim. Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing. Germany. doi:10.5194/se-8-1193-2017.
Gilgannon, James, Fusseis, Florian, Menegon, Luca, Regenauer-Lieb, Klaus, and Buckman, Jim. 2017. "Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing". Germany. doi:10.5194/se-8-1193-2017.
@article{osti_1459997,
title = {Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing},
author = {Gilgannon, James and Fusseis, Florian and Menegon, Luca and Regenauer-Lieb, Klaus and Buckman, Jim},
abstractNote = {Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.},
doi = {10.5194/se-8-1193-2017},
journal = {Solid Earth (online)},
number = 6,
volume = 8,
place = {Germany},
year = {2017},
month = {12}
}