Titre :

Argon storage and diffusion in Earth’s upper mantle

Auteur(s) :

Delon, Rémi [Auteur]
Centre de Recherches Pétrographiques et Géochimiques [CRPG]
Demouchy, Sylvie [Auteur]
Géosciences Montpellier
Marrocchi, Yves [Auteur]
Centre de Recherches Pétrographiques et Géochimiques [CRPG]
Bouhifd, Mohamed Ali [Auteur]
Laboratoire Magmas et Volcans [LMV]
Cordier, Patrick [Auteur]
Unité Matériaux et Transformations (UMET) - UMR 8207
Addad, Ahmed [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Burnard, Pete G. [Auteur]
Centre de Recherches Pétrographiques et Géochimiques [CRPG]

Titre de la revue :

Geochimica et Cosmochimica Acta

Nom court de la revue :

Geochimica et Cosmochimica Acta

Numéro :

253

Pagination :

1-18

Éditeur :

Elsevier BV

Date de publication :

2019-05

ISSN :

0016-7037

Mot(s)-clé(s) en anglais :

Argon
Diffusion
Olivine
Polycrystalline
Grain boundary
Earth's mantle
Storage

Discipline(s) HAL :

Planète et Univers [physics]
Physique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]

Résumé en anglais : [en]

In this study, fine-grained polycrystalline olivine was doped with argon at static high pressure (0.30 ± 0.01 GPa) and high temperature (1050 ± 25 °C) conditions during 24 h in a Paterson press, and analysed using a ...
Lire la suite >In this study, fine-grained polycrystalline olivine was doped with argon at static high pressure (0.30 ± 0.01 GPa) and high temperature (1050 ± 25 °C) conditions during 24 h in a Paterson press, and analysed using a step-heating extraction protocol coupled with noble gas mass spectrometry to investigate argon storage and diffusivity in Earth’s upper mantle. Our results show that a single diffusion mechanism controlled argon diffusion in our samples during the step heating experiments. Effective Ar diffusion in olivine has a low activation energy, implying that argon diffusivity is governed by both grain boundary and lattice diffusion. Mean values of lattice diffusion parameters obtained from our results and by reprocessing literature data are Ea = 166 ± 44 kJ mol−1 and D0 = 10−7.04 ± 1.13 m2·s−1, and grain boundary diffusion parameters determined from our data are Ea = 22 ± 5 kJ·mol−1 and D0 = 10−12.87 ± 0.3 m2·s−1. Isotopic diffusivity ratios were constant and close to the values determined by Graham’s law in the C-regime (i.e., bulk diffusion dominated by grain boundary diffusion) and A-regime (i.e., bulk diffusion controlled by grain boundary and lattice diffusion in proportion to the segregation of Ar between those sites), but varied in the B-regime (i.e., bulk diffusion controlled by both grain boundary and lattice diffusion in a complex manner), implying a higher isotopic fractionation in the kinetic B-regime. Extrapolation to typical mantle grain sizes implies that around 22% of the argon in the upper mantle can be stored at grain boundaries and that effective diffusion is mostly in the A-regime, suggesting a low isotopic fractionation and diffusivities faster than lattice diffusivities alone. The consideration of grain boundaries as a potential Ar storage site can modify equilibrium during partial melting and significantly enrich a liquid in Ar during fluid percolation. The grain size dependence of Ar storage and diffusivity highlights the underestimated role of grain boundaries in the upper mantle, especially in zones of reduced grain size (via dynamic recrystallization) possibly followed by fluid percolation and/or partial melting, such as in subduction zones or below oceanic ridges.Lire moins >

Langue :

Anglais

Audience :

Internationale

Vulgarisation :

Non

Projet ANR :

Incorporation et diffusion des gaz rares dans les joints de grain.

Établissement(s) :

Université de Lille
CNRS
INRA
ENSCL

Collections :

• Unité Matériaux et Transformations (UMET) - UMR 8207

Équipe(s) de recherche :

Plasticité

Date de dépôt :

2019-04-03T12:49:09Z
2019-04-04T12:22:49Z
2019-04-04T12:58:15Z
2019-04-09T14:39:57Z
2019-04-15T14:22:08Z
2019-05-28T12:08:21Z
2023-06-30T09:08:58Z