Title :

Mantle metasomatic influence on water contents in continental lithosphere: New constraints from garnet pyroxenite xenoliths (France & Cameroon volcanic provinces)

Author(s) :

Azevedo-Vannson, Samantha [Auteur]
Centre de Recherches Pétrographiques et Géochimiques [CRPG]
Institut de minéralogie, de physique des matériaux et de cosmochimie [IMPMC]
France, Lydéric [Auteur]
Centre de Recherches Pétrographiques et Géochimiques [CRPG]
Ingrin, Jannick [Auteur]
Unité Matériaux et Transformations - UMR 8207 [UMET]
Chazot, Gilles [Auteur]
Laboratoire Géosciences Océan [LGO]

Journal title :

Chemical Geology

Volume number :

575

Pages :

120257

Publisher :

Elsevier BV

Publication date :

2021-08-05

ISSN :

0009-2541

English keyword(s) :

Nominally anhydrous minerals
Garnet pyroxenites
Hydroxyl
Mantle metasomatism
Adamawa Volcanic Plateau
French Massif Central

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]

Quantifying water contents in the lithospheric mantle is key to our understanding of global geodynamics, mantle composition, and related physical properties. Most mantle lithologies (peridotite) contain little water (~50 ...
Show more >Quantifying water contents in the lithospheric mantle is key to our understanding of global geodynamics, mantle composition, and related physical properties. Most mantle lithologies (peridotite) contain little water (~50 ppm), but petrological heterogeneities such as pyroxenites are more hydrous (~300 ppm) relative to the mantle rocks. Pyroxenites also melt at lower temperatures than peridotites and are thus important to magma genesis. Thus, quantifying pyroxenite water contents provides new information on the distribution of water in the mantle. Here, we present phase-specific FTIR measurements of the water contents in pyroxenite mantle xenoliths from two continental lithospheric domains that experienced intense metasomatism: the French Massif Central (FMC, France) and the Adamawa Volcanic Plateau (AVP, Cameroon). The AVP garnet pyroxenites are more hydrated ([H2O]Clinopyroxene = 386–685 ppm; [H2O]Orthopyroxene = 124–155 ppm; [H2O]Garnet < 0.5 ppm) than FMC ones ([H2O]Clinopyroxene = 112–465 ppm; [H2O]Orthopyroxene = 61–104 ppm; [H2O]Garnet < 0.5 ppm). These water concentrations are homogenous at the grain and correlate with equilibrated major element concentrations, indicating that they are representative of lithospheric water, although the FMC pyroxenites were dehydrated during metasomatism by a carbonatitic fluid (based on the correlation between LaN/SmN and Ti/Eu ratios); the water contents of AVP pyroxenites were likely not affected by metasomatism. FMC pyroxenites show peculiar FTIR spectra that may reflect the preferential dehydration of specific sites in the pyroxene structure. In both regions, metasomatism modified the light rare Earth element contents (e.g., Ce) of the pyroxenites, resulting in highly variable H2O/Ce ratios. Therefore, we conclude that the utility of the H2O/Ce ratio to identify the involvement of pyroxenites in magmas genesis is limited.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 :

2021-04-30T09:05:36Z
2021-05-17T13:36:24Z
2023-07-07T09:17:32Z