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URN: urn:nbn:de:bsz:25-opus-4965
URL: http://www.freidok.uni-freiburg.de/volltexte/496/


Lang, Marcus

Formation and segregation of melts during deformation : an approach with analogue material

Bildung und Segregation von Schmelzen bei Deformation : ein Ansatz mit Analogmaterial

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Kurzfassung in Deutsch

Field evidence from natural partial molten systems like migmatites
indicate a close relationship between melt segregation and
deformation. To study this phenomena we conducted experiments with
rock analogues consisting of mixtures of LiNO3 and KNO3
as a melting component and crushed baryte featuring as a
non-melting framework. Four sets of experiments with strain rates
from 1x10E-5 s-1 to 5x10E-4 s-1 at
melt contents between 4.4 , 8.8 , 17.7 and 26.6 have
been conducted. Hot isostatically pressed cylindrical samples of 35 mm
diameter and approximately 60 mm height have been sintered and
uni-axially deformed at 133.5°C to axial strains of 30-50 with
instantaneous record of strength. With this setup we enable an
efficient voluminous melt segregation in three dimensions.

The chosen material is scaled to simulate the melt movement of
granitic melts with a viscosity of 3.6x10E+7 Pa s and strain
rates of 1.1x10E-10 s-1 in a framework with grain sizes and
melt fractions similar to those in nature. Measured strengths are
10E-3 the natural constraint strength of partially molten
rocks. Longest experiment duration scale to 100 years in nature.

Bulk strength decreases with low strain rate and high melt
content without a rapid decrease at critical melt contents as
inferred from literature (Arzi, 1978). At higher melt fractions
samples started to harden which was interpreted as the effect of
segregation which in turn lead to hardening of the melt depleted
areas.

Polished sections and statistical analysis of the spatial melt
distribution and melt area proportion added to the understanding
of segregational features. Efficient melt segregation is initiated
at melt fraction higher than 4.3, where below this limit melt
sticks in interstitial pore and can not accumulate. Lower strain
rates and the development of favorable structures such as shear
zone further increase the efficiency of melt segregation.


SWD-Schlagwörter: Deformation , Partielle Schmelze , Baryt , Segregation, Rheologie
Freie Schlagwörter (deutsch): Migmatite, Analog , Nitrat ,
Freie Schlagwörter (englisch): melt , deformation , migmatite , analogue , rheology
Institut: Geologisches Institut
Fakultät: Geowissenschaftliche Fakultät (bis Sept. 2002)
DDC-Sachgruppe: Geowissenschaften, Geologie
Dokumentart: Dissertation
Erstgutachter: Behrmann, Jan H. (Prof. Dr.)
Sprache: Englisch
Tag der mündlichen Prüfung: 30.04.2002
Erstellungsjahr: 2002
Publikationsdatum: 25.07.2002
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