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| Titel |
Large strain rheology of syn-tectonic melting and crystallizing metapelites |
| VerfasserIn |
Santanu Misra, Jean-Pierre Burg |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046298
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| Zusammenfassung |
| This study investigates the rheological behaviour of metapelitic rocks undergoing
synkinematic melting and subsequent crystallization of melt during progressive deformation.
Torsion experiments on synthetic quartz-mica rock samples close to pelitic compositions
were performed at 300 MPa confining pressure and 750oC with a constant strain rate
(Ëγ =3x10-4) for a range of finite shear strains (γ = 0.5-15). The deformed samples were
studied along the longitudinal tangential (LT) and axial (LA) sections to obtain data along a
range of strain rates for a given finite strain and vice-versa. The results showed that
deformation plays an important role on the kinetics of partial melting and crystallization.
With increasing strain rate, amount and rate of crystallization is the volumetrically dominant
process compared to partial melting at a given finite strain. In contrast, when the strain rate
is constant, partial melting is dominates crystallization up to moderate strain (γg
< g5). The dominant process reverses at higher strain and the system shows more
crystallization than partial melting. Partial melting coupled with strong strain softening (~
60%) in the creep behaviour started at relatively low shear strains (γ = 2-4). With
further shearing (γ = 4-10) creep became steady state flow associated with nucleation
of tiny, new crystals. At higher shear strain (γ = 10-15), crystallization of these
new minerals was coeval with small strain hardening until ultimate failure of the
sample. A continuous increase of the stress exponent (n) from 3 (at γ = 1) to 28 (at γ
= 5) was noted with progressive deformation, indicating a transition of the flow
law. Depending on the melt and solid proportions in the system, the new and more
realistic experimental data established that the large strain rheology and mechanical
response is complex and does not necessarily follow power law flow behaviour. |
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