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Deformation of silicate garnets; brittle-ductile transition and its geological implications

Zichao Wang and Shaocheng Ji
Deformation of silicate garnets; brittle-ductile transition and its geological implications (in Mineral-scale processes in metamorphic petrology; the Kretz volume, T. Rivers (editor), D. R. M. Pattison (editor) and R. F. Martin (editor))
The Canadian Mineralogist (April 1999) 37, Part 2: 525-541

Abstract

To understand the deformation behaviour of garnets, a series of experiments were performed on six representative garnets at 1173-1673 K, strain-rates of 10 (super -7) to 10 (super -4) /s and well-confined thermodynamic conditions. It was found that the critical T (T (sub c) ) for the brittle-ductile transition of garnet deformation, in terms of melting T (T (sub m) ) and strain-rate (<$>epsilon <$>). can be described by an empirical equation T (sub c) = T (sub m) (1.043 + or - 0.032) + (0.030 + or - 0.001) log (<$>epsilon <$>)]. It is suggested that crystal plasticity, enhanced by the activation of dislocation glide, is responsible for the brittle-ductile transition. Extrapolation to geological strain-rates (10 (super -16) to 10 (super -14) /s) suggests that the brittle-ductile transition of garnets in nature occurs at T > 0.65-0.70 T (sub m) . This indicates that almandine, pyralspite and grossular can be deformed in ductile fashion under extremely high T (> 1123 K). It is concluded that garnets are mostly rigid and brittle in the crust, but ductile as long as the conditions of high T and low strain-rate are satisfied.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 37, Part 2
Title: Deformation of silicate garnets; brittle-ductile transition and its geological implications
Title: Mineral-scale processes in metamorphic petrology; the Kretz volume
Author(s): Wang, ZichaoJi, Shaocheng
Author(s): Rivers, T.editor
Author(s): Pattison, D. R. M.editor
Author(s): Martin, R. F.editor
Affiliation: Universite de Montreal, Department of Geologie, Montreal, Canada
Pages: 525-541
Published: 199904
Text Language: English
Summary Language: French
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 57
Accession Number: 1999-067544
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199923
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