Title :

Electrical conductivity of omphacite and garnet indicates limited deep water recycling by crust subduction

Author(s) :

Liu, Hanyong [Auteur]
Nanjing University [NJU]
Zhang, Kai [Auteur]
Nanjing University [NJU]
Ingrin, Jannick [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Yang, Xiaozhi [Auteur]
Nanjing University [NJU]

Journal title :

Earth and Planetary Science Letters

Volume number :

559

Pages :

116784

Publisher :

Elsevier BV

Publication date :

2021-04-01

ISSN :

0012-821X

English keyword(s) :

electrical conductivity
omphacite and garnet
deep water recycling
crust subduction
experimental studies

HAL domain(s) :

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

English abstract : [en]

It is usually stated that oceanic crust recycling at subduction zones introduces large quantities of water into Earth’s interior. However, it remains clouded how much water is recycled to the deep mantle. This is largely ...
Show more >It is usually stated that oceanic crust recycling at subduction zones introduces large quantities of water into Earth’s interior. However, it remains clouded how much water is recycled to the deep mantle. This is largely due to the challenge in directly sampling, and analyzing the water content of, a deep subducting crust. The subducting crust below ~30 km depth is dominated by omphacite and garnet in eclogite-facies rocks. Here we have determined the electrical conductivity of omphacite and garnet in representative subduction-related eclogites, each with varying contents of Fe and H2O that are key in electrical conduction. Considering the measured conductivity, the eclogite chemistry by geochemical investigations and the highly resistive property of subducting crusts by geophysical surveys, we demonstrate that, at 70-120 km depths in the subducting crust, the H2O contents of omphacite and garnet are strikingly small, with the maximum value being <400 and <80 ppm in the former and latter, respectively. The very small water contents indicate extremely water-poor conditions, or very low water activity, during the eclogite-facies metamorphism and in the system. This further implies the absence of appreciated amounts of hydrous phases such as amphibole and chlorite in the matrix, because of the strong ability of omphacite and garnet in hosting water as documented in natural samples. We suggest that the recycling of water to the deep mantle by oceanic crust subduction is limited. The results are important for modeling the conductivity of subducting slabs and understanding the deep water circulation.Show less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

Administrative institution(s) :

Université de Lille
CNRS
INRA
ENSCL

Collections :

• Unité Matériaux et Transformations (UMET) - UMR 8207

Research team(s) :

Matériaux Terrestres et Planétaires

Submission date :

2021-02-04T16:43:10Z
2021-02-08T13:21:17Z