Titre :

Kinetic D/H fractionation during hydration and dehydration of silicate glasses, melts and nominally anhydrous minerals

Auteur(s) :

Roskosz, Mathieu [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Deloule, Etienne [Auteur]
Centre de Recherches Pétrographiques et Géochimiques [CRPG]
Ingrin, Jannick [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Depecker, Christophe [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Laporte, Didier [Auteur]
Laboratoire Magmas et Volcans [LMV]
Merkel, Sébastien [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Remusat, Laurent [Auteur]
Institut de minéralogie, de physique des matériaux et de cosmochimie [IMPMC]
Leroux, Hugues [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]

Titre de la revue :

Geochimica et Cosmochimica Acta

Numéro :

233

Pagination :

14-32

Date de publication :

2018

Discipline(s) HAL :

Planète et Univers [physics]/Astrophysique [astro-ph]
Physique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]
Physique [physics]/Astrophysique [astro-ph]
Planète et Univers [physics]/Sciences de la Terre
Chimie/Matériaux
Physique [physics]/Physique [physics]/Géophysique [physics.geo-ph]

Résumé en anglais : [en]

The distribution of hydrogen isotopes during diffusion-driven aqueous processes in silicate glasses, melts and crystals was investigated. Hydration/dehydration experiments were performed on silica glasses at 1000 °C and ...
Lire la suite >The distribution of hydrogen isotopes during diffusion-driven aqueous processes in silicate glasses, melts and crystals was investigated. Hydration/dehydration experiments were performed on silica glasses at 1000 °C and 1 bar total pressure. Dehydration triggered by decompression-driven bubble nucleation and growth was performed on rhyolitic melts at 800 °C and a few hundred MPa. Hydrogen extraction from a nominally anhydrous mineral (grossular) single crystal was carried out at 800 °C and ambient pressure. After these three series of experiments, pronounced water (sensu lato) concentration profiles were observed in all recovered samples. In the grossular single-crystal, a large spatial variation in H isotopes (δD variation > 550‰) was measured across the sample. This isotopic distribution correlates with the hydrogen extraction profile. The fit to the data suggests an extreme decoupling between hydrogen and deuterium diffusion coefficients (DH and DD respectively), akin to the decoupling expected in a dilute ideal gas (DH/DD ≈ 1.41). Conversely, no measurable spatially- and time-resolved isotopic variations were measured in silicate glasses and melts. This contrasted behavior of hydrogen isotopes likely stands in the different water speciation and solution mechanisms in the three different materials. Glasses and melts contain essentially hydroxyl and molecular water groups but the mobile species is molecular water in both cases. Protonated defects make up most of the water accommodated in grossular and other nominally anhydrous minerals (NAM). These defects are also the mobile species that diffuse against polarons. These results are crucial to accurately model the degassing behavior of terrestrial and lunar magmas and to derive the initial D/H of water trapped in fluid inclusions commonly analyzed in mantle NAMs, which suffered complex geological histories.Lire moins >

Langue :

Anglais

Comité de lecture :

Oui

Audience :

Internationale

Vulgarisation :

Non

Établissement(s) :

Université de Lille
ENSCL
CNRS
INRA

Collections :

• Unité Matériaux et Transformations (UMET) - UMR 8207

Équipe(s) de recherche :

Matériaux Terrestres et Planétaires

Date de dépôt :

2019-05-17T09:15:08Z
2019-10-11T12:53:46Z
2021-03-01T10:42:55Z