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Poster communications

Quantifying crystal-melt segregation in dykes

Abstract : 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 (), the density contrast between crystals and melt (), 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 and Ac are large, and lowest for large pressure gradient (Pd) and/or large values ofWd. 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 , encompassing a wide range of typical parameters encountered in terrestrial magmatic systems.
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Poster communications
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https://hal-insu.archives-ouvertes.fr/insu-01137665
Contributor : Isabelle Dubigeon <>
Submitted on : Tuesday, March 31, 2015 - 10:43:55 AM
Last modification on : Tuesday, July 9, 2019 - 2:26:04 PM

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  • HAL Id : insu-01137665, version 1

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Philippe Yamato, Thibault Duretz, Dave May, Romain Tartese. Quantifying crystal-melt segregation in dykes. European Geoscience Union General Assembly 2015, Apr 2015, Vienne, Austria. Geophysical Research abstracts, 17, pp.EGU2015-5905, 2015. ⟨insu-01137665⟩

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