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| Titel |
Distribution of melt during Poiseuille flow of partially molten rocks |
| VerfasserIn |
Alejandra Quintanilla-Terminel, Amanda Dillman, David Kohlstedt |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130508
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| Publikation (Nr.) |
 EGU/EGU2016-10773.pdf |
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| Zusammenfassung |
| The mechanisms of melt extraction from the Earth’s partially molten mantle are a key factor
in the chemical and physical evolution of our planet and therefore are the topic of intense
research. Since such processes cannot be observed directly, most of our understanding
of the dynamics of partially molten rock relies on numerical models. Laboratory
experiments are important for testing the validity of models at scales that we can
observe.
We designed a set of experiments to investigate the role of viscous anisotropy on melt
segregation in partially molten rocks through Poiseuille flow. Partially molten rock samples
composed of forsterite plus a few percent melt of different composition (anorthite, albite or
lithium silicate) were prepared from high-purity nano-powders and taken to T = 1300oC at P
= 0.1 MPa. The melt composition was varied in order to vary its viscosity. The partially
molten samples were then extruded through a channel of circular cross section under a fixed
pressure gradient. Different extrusion assemblies and consequently different flow geometries
were explored.
The melt distribution in the channel was subsequently mapped using image analysis on
backscattered electron microscopy images and energy dispersive x-ray spectroscopy maps. In
all experiments, melt segregates from the center toward the outer radius of the channel with
the melt fraction at the outer radius increasing to at least twice that at the center.
Furthermore, melt enriched areas are also observed in the center of the channel. The
shape of the melt distribution depends on the extrusion geometry and on the melt
viscosity.
The segregation of melt toward the outer radius of the channel is consistent with the
base-state melt segregation as predicted by viscous anisotropy theory developed by Takei and
Holtzman (2009) and Takei and Katz (2014). However, the melt distribution profiles observed
in our experiments have steeper gradients than the base-state melt segregation profiles
described in the numerical solutions presented by Allwright & Katz (2014). This discrepancy
may be related to the propagation of melt-enriched bands within the base state. |
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