Thermomechanical analysis of strain localization in a ductile detachment zone

Details

Serval ID
serval:BIB_385868A04023
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Thermomechanical analysis of strain localization in a ductile detachment zone
Journal
Journal of Geophysical Research - Solid Earth
Author(s)
Mulch A., Teyssier C., Cosca M.A., Vennemann T.W.
ISSN-L
0148-0227
Publication state
Published
Issued date
2006
Peer-reviewed
Oui
Volume
111
Pages
B12405
Language
english
Abstract
At the latitude of the Thor-Odin dome (British Columbia) the Columbia River Detachment defines the eastern margin of the Shuswap metamorphic core complex and localizes in a 1 km thick muscovite-bearing quartzite mylonite. We present a combined Ar-40/Ar-39, (micro) structural, and oxygen isotope study of the deformation history in the detachment and evaluate the spatial and temporal relationships between microstructure formation and localization of strain. High-precision Ar-40/Ar-39 geochronology from different levels in the mylonite delineates a pattern of increasingly younger (49.0 to 47.9 Ma) deformation ages in deeper levels of the mylonitic footwall. The correlation of Ar-40/Ar-39 ages with decreasing deformation temperatures (similar to 550 degrees-400 degrees C) in the top 200 m of the mylonite indicates that deformation migrated downward from the contact with the hanging wall. Strain localization was diachronous in progressively deeper levels of the footwall and was likely controlled by fluid-assisted strain hardening due to advective heat removal and contemporaneous reaction weakening due to dissolution-reprecipitation of white mica. The observed constant high-stress microstructures across the entire detachment indicate that flow stress was buffered by the interplay of strain rate and temperature, where high strain rates at elevated temperature produced the same microstructure as lower strain rates under decreasing temperature conditions. The combined data suggest that the complex interplay among temporally nonuniform rates of footwall exhumation, heat advection, and embrittlement by meteoric fluids strongly determines the thermomechanical behavior of extensional detachments.
Open Access
Yes
Create date
30/09/2012 11:40
Last modification date
20/08/2019 13:27
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