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

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.<br><br>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.<br><br>Bulk strength decreases with low strain rate and high melt content without a rapid decrease at critical melt contents as<br>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.<br><br>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.

Author dc:creator

• Lang, Marcus

Contributors dc:contributor

• Behrmann, Jan H.

• melt
• deformation
• migmatite
• analogue
• rheology

Repository record source_url

https://freidok.uni-freiburg.de/data/496

OAI identifier oai:identifier

oai:freidok.uni-freiburg.de:496