Major softening at brittle-ductile transition due to interplay between chemical and deformation processes: An insight from evolution of shear bands in the South Armorican Shear Zone

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F16%3A10323822" target="_blank" >RIV/00216208:11310/16:10323822 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.1002/2015JB012319" target="_blank" >http://dx.doi.org/10.1002/2015JB012319</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1002/2015JB012319" target="_blank" >10.1002/2015JB012319</a>

Result language

angličtina

Original language name

Major softening at brittle-ductile transition due to interplay between chemical and deformation processes: An insight from evolution of shear bands in the South Armorican Shear Zone

Original language description

The formation of S-C/C' fabrics in the South Armorican Shear Zone has been evaluated by detailed microstructural study where the focus was given to initiation and early evolution of the C/C' fabric shear bands. Our observations suggest that the S-C/C' fabrics formed at distinct temperature conditions indicating >550oC for the S fabric and 300-350oC at 100-400 MPa for the C/C' fabric shear bands. The evolving microstructure within shear bands documents switches in deformation mechanisms related to positive feedbacks between deformation and chemical processes and imposes mechanical constraints on the evolution of the brittle-ductile transition in the continental transform fault domains. Three stages of shear band evolution have been identified. Stage I corresponds to initiation of shear bands via formation of microcracks with possible yielding differential stress of up to 250 MPa. Stage II is associated with subgrain rotation recrystallization and dislocation creep of quartz and coeval dissolution-precipitation creep of microcline. Recrystallized quartz grains show continual increase in size and decrease in stress and strain rates from 94 MPa to 17-26 MPa and 3.8 x 10-12 s-1 - 8 x 10-14 s-1 associated with deformation partitioning into weaker microcline layer and shear band widening. The quartz mechanical data allowed us to set some constrains for coeval dissolution-precipitation of microcline which at our estimated pressure-temperature conditions suggests creep at 17-26 MPa differential stress and 3.8 x 10-13 s-1 strain rate. Stage III is characterized by localized slip along white mica bands accommodated by dislocation creep at strain rate 3.8 x 10-12 s-1 and stress 9.36 MPa. Our mechanical data point to dynamic evolution of the studied brittle-ductile transition characterized by major weakening to strengths ~10 MPa. Such nonsteady state evolution may be common in crustal shear zones especially when phase transformations are involved.

Czech name

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Czech description

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Type

J_x - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)

CEP classification

DB - Geology and mineralogy

OECD FORD branch

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Project

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Continuities

S - Specificky vyzkum na vysokych skolach<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2016

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH

ISSN

2169-9313

e-ISSN

—

Volume of the periodical

121

Issue of the periodical within the volume

2

Country of publishing house

US - UNITED STATES

Number of pages

25

Pages from-to

1158-1182

UT code for WoS article

000373084400041

EID of the result in the Scopus database

2-s2.0-84959139665