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| Titel |
Simple shear deformation of partially molten aplite |
| VerfasserIn |
Michael Stipp, Jan Tullis, Alfons Berger |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078140
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| Zusammenfassung |
| The tectonic processes which are important for melt distribution and transport in the
intermediate and lower crust and which can result in crustal weakening are not yet well
understood. Natural migmatites are usually overprinted by annealing and retrogression
during uplift and exhumation, largely obliterating the deformation structures and
microstructures of their partially molten history. Deformation experiments on partially
molten crustal rocks have so far been conducted in pure shear geometry and mostly
under low confining pressures in the brittle deformation field, both of which are
not representative of nature. We carried out deformation experiments in simple
shear that predominates in the crust and especially crustal shear zones. Undrained
experiments were carried out on Enfield aplite at ~1.5 GPa, 900Ë -1000Ë C, and
-¤ 5*10-6 s-1, conditions which favor crystal plastic deformation of quartz and
feldspar (Dell’Angelo and Tullis, 1988). Sample slices 1.0-1.5 mm thick were placed
between the shear pistons with the shear plane at a 45Ë -angle to the compression
direction. Maximum shear strain in the experiments is γ -2.8. Despite difficulties in
controlling the melt content by varying the amount of added water, we were able to
achieve the full range of brittle to crystal plastic deformation mechanisms. With
decreasing melt content Enfield aplite displays a transition from discrete fracturing at a
high angle (~70-90Ë ) to the shear plane (>20 vol.% melt), to cataclastic shearing
(10-20 vol.% melt) and to crystal plastic deformation ( |
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