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| Titel |
Quantifying crystal-melt segregation in dykes |
| VerfasserIn |
Philippe Yamato, Thibault Duretz, Dave A. May, Romain Tartèse |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106245
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| Publikation (Nr.) |
 EGU/EGU2015-5905.pdf |
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| Zusammenfassung |
| The dynamics of magma flow is highly affected by the presence of a crystalline load. During
magma ascent, it has been demonstrated that crystal-melt segregation constitutes a viable
mechanism for magmatic differentiation. However, the influences of crystal volume fraction,
geometry, size and density on crystal melt segregation are still not well constrained. In order
to address these issues, we performed a parametric study using 2D direct numerical
simulations, which model the ascension of crystal-bearing magma in a vertical dyke. Using
these models, we have characterised the amount of segregation as a function of
different quantities including: the crystal fraction (Ï), the density contrast between
crystals and melt (δÏ), the size of the crystals (Ac) and their aspect ratio (R). Results
show that crystal aspect ratio does not affect the segregation if R is small enough
(long axis smaller than ~1/6 of the dyke width, Wd). Inertia within the system was
also found not to influence crystal-melt segregation. The degree of segregation
was however found to be highly dependent upon other parameters. Segregation is
highest when δÏ and Ac are large, and lowest for large pressure gradient (Pd) and/or
large values of Wd. These four parameters can be combined into a single one, the
Snumber, which can be used to quantify the segregation. Based on systematic numerical
modelling and dimensional analysis, we provide a first order scaling law which allows
quantification of the segregation for an arbitrary Snumber and Ï, encompassing
a wide range of typical parameters encountered in terrestrial magmatic systems. |
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