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Conference Papers Year : 2022

Segregation and extraction of late magmatic melt and fluids in mushes: experimental approach at high pressure

Abstract

The crustal mush (i.e., mixture of crystals and silicate liquid whose mobility is inhibited by a high fraction of solid particles) has acquired more importance in the last decade, replacing the traditional concept of magma chamber. It is still unclear how the deformation is localized in the mushes and how this localization can control the segregation and extraction of the melt from the crystalline network. In this study, we performed syn-deformational melt-extraction experiments on haplotonalitic magma.

In order to create a hydrated mush (3 wt% H2O) composed of euhedral plagioclases crystals capable of covering the expected extraction window phase (Φ: 0.52 - 0.58, 700 ° C A pervasive SPO characterized by a main preferred orientation at 45° from the dextral shear direction develops with finite strains γ<~1 and low strain rates. At γ>1, crystalline grains domains appear isolated, contacting and aligned alike, parallel to the shear direction (Y-bands) or to the main stress direction (C-bands). As the finite strain and strain rate increase, thickening of these crystalline grains domains occurs, resulting in the emergence of shear zones that stretch lengthwise with increasing strain and form an anastomosing array. Melt migration was not observed in any of the experiments, neither in the main pervasive fabric nor in the subsequently generated shear zones.

We conclude that: 1) in discrete crystal orientation domains begins the initiation of strain localisation in magmatic mushes as the stress propagation over the crystal network is eased by the contact interactions between them; and 2) we were not able to get the melt extraction hence a possible requirement is higher crystal content.

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Dates and versions

insu-04092123 , version 1 (09-05-2023)

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Monica Spagnoli, Laurent Arbaret, Rémi Champallier, Jacques Précigout, Mikael Laumonier. Segregation and extraction of late magmatic melt and fluids in mushes: experimental approach at high pressure. AGU Fall Meeting 2022, 2022, à renseigner, Unknown Region. ⟨insu-04092123⟩
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