Tracking the changing oxidation state of Erebus magmas, from mantle to surface, driven by magma ascent and degassing - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Earth and Planetary Science Letters Année : 2014

Tracking the changing oxidation state of Erebus magmas, from mantle to surface, driven by magma ascent and degassing

Résumé

The conventional view holds that the oxidation state of a mantle-derived degassed magma reflects its source. During magma ascent and degassing the oxidation state is thought to follow a redox buffer. While this view has been challenged by petrological data, geochemical models and volcanic gas measurements, the fingerprints of such redox changes and their driving forces have not hitherto been captured by an integrated study. Here, we track the redox evolution of an alkaline magmatic suite at Erebus volcano, Antarctica, from the mantle to the surface, using X-ray absorption near-edge structure (XANES) spectroscopy at the iron and sulphur K-edges. We find that strong reduction of Fe and S dissolved in the melt accompanies magma ascent. Using a model of gas-melt chemical equilibria, we show that sulphur degassing is the driving force behind this evolutionary trend, which spans a wide compositional and depth range. Our results explain puzzling shifts in the oxidation state of gases emitted from Erebus volcano, and indicate that, where sulphur degassing occurs, the oxidation states of degassed volcanic rocks may not reflect their mantle source or co-eruptive gas phase. This calls for caution when inferring the oxidation state of the upper mantle from extrusive rocks and a possible re-assessment of the contribution of volcanic degassing to the early Earth's atmosphere and oceans. The relationship between magma redox conditions and pressure (depth) emphasises the value of measuring redox couples in gases emitted from volcanoes for the purposes of operational forecasting.
Fichier principal
Vignette du fichier
Mantle_to_surface_tracking_EPSL_Revised_v4.pdf (4.84 Mo) Télécharger le fichier
Vignette du fichier
Fig.jpg (1.64 Mo) Télécharger le fichier
Supplementary_Mantle_to_surface_tracking_SI_EPSL_Revised.pdf (1.39 Mo) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)
Format : Figure, Image
Format : Autre
Loading...

Dates et versions

insu-00966727 , version 1 (27-03-2014)

Licence

Paternité - Pas d'utilisation commerciale - Pas de modification

Identifiants

Citer

Yves Moussallam, Clive Oppenheimer, Bruno Scaillet, Fabrice Gaillard, Philip R. Kyle, et al.. Tracking the changing oxidation state of Erebus magmas, from mantle to surface, driven by magma ascent and degassing. Earth and Planetary Science Letters, 2014, 393, pp.200-209. ⟨10.1016/j.epsl.2014.02.055⟩. ⟨insu-00966727⟩
1594 Consultations
660 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More