Argon storage and diffusion in Earth’s ...
Document type :
Article dans une revue scientifique: Article original
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Title :
Argon storage and diffusion in Earth’s upper mantle
Author(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]
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]
Journal title :
Geochimica et Cosmochimica Acta
Abbreviated title :
Geochimica et Cosmochimica Acta
Volume number :
253
Pages :
1-18
Publisher :
Elsevier BV
Publication date :
2019-05
ISSN :
0016-7037
English keyword(s) :
Argon
Diffusion
Olivine
Polycrystalline
Grain boundary
Earth's mantle
Storage
Diffusion
Olivine
Polycrystalline
Grain boundary
Earth's mantle
Storage
HAL domain(s) :
Planète et Univers [physics]
Physique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]
Physique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]
English abstract : [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 ...
Show more >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.Show less >
Show more >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.Show less >
Language :
Anglais
Audience :
Internationale
Popular science :
Non
Administrative institution(s) :
Université de Lille
CNRS
INRA
ENSCL
CNRS
INRA
ENSCL
Collections :
Research team(s) :
Plasticité
Submission date :
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
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
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