Dehydration reactions and micro/nanostructures in experimentally-deformed serpentinites

High-T torsion experiments on lizardite + chrysotile serpentinites produced mineralogical and micro/nanostructural changes, with important implications in rheological properties. High-resolution TEM showed that specimens underwent ductile [by microkinking and (001) interlayer glide] and brittle defo...

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Bibliographic Details
Published in:Contributions to mineralogy and petrology 2009-03, Vol.157 (3), p.327-338
Main Authors: Viti, Cecilia, Hirose, Takehiro
Format: Article
Language:English
Subjects:
Earth and Environmental Science
Earth Sciences
Geochemistry
Geology
Metamorphic rocks
Microstructure
Mineral Resources
Mineralogy
Minerals
Nanostructured materials
Original Paper
Petrology
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Summary:High-T torsion experiments on lizardite + chrysotile serpentinites produced mineralogical and micro/nanostructural changes, with important implications in rheological properties. High-resolution TEM showed that specimens underwent ductile [by microkinking and (001) interlayer glide] and brittle deformation (by microfracturing), together with dehydration and break-down reactions. Lizardite is affected by polytypic disorder and microkinking [kink axial planes at high angle with respect to (001) planes], that were not present in the initial ordered 1T-lizardite. Chrysotile fibres are deformed, resulting in elliptical cross-sections, with strong loss of interlayer cohesion. Both lizardite and chrysotile break down to a fine intergrowth of olivine (up to 200 nm), talc (up to 30 nm) and poorly-crystalline material. Lizardite-out reaction preferentially occurs at kink axial planes, representing sites of preferential strain and enhanced reactivity; conversely, chrysotile break-down is a bulk process, resulting in large healed olivine aggregates, up to micrometric in size. Overall observations suggest that dehydration and break-down reactions are more advanced in chrysotile than in lizardite.
ISSN:0010-7999
1432-0967
DOI:10.1007/s00410-008-0337-6