Bonding of xenon to oxygen in magmas at depth - Archive ouverte HAL Access content directly
Journal Articles Earth and Planetary Science Letters Year : 2017

Bonding of xenon to oxygen in magmas at depth

(1) , (2) , (1) , (3) , (4) , (5)
1
2
3
4
5

Abstract

The field of noble gases chemistry has witnessed amazing advances in the last decade with over 100 compounds reported including Xe oxides and Xe–Fe alloys stable at the pressure-temperature conditions of planetary interiors. The chemistry of Xe with planetary materials is nonetheless still mostly ignored, while Xe isotopes are used to trace a variety of key planetary processes from atmosphere formation to underground nuclear tests. It is indeed difficult to incorporate the possibility of Xe reactivity at depth in isotopic geochemical models without a precise knowledge of its chemical environment. The structure of Xe doped hydrous silica-rich melts is investigated by in situ high energy synchrotron X-ray diffraction using resistive heating diamond anvil cells. Obtained pair distribution functions reveal the oxidation of Xe between 0.2 GPa and 4 GPa at high T up to 1000 K. In addition to the usual interatomic distances, a contribution at 2.05 ± 0.05 Å is observed. This contribution is not observed in the undoped melt, and is interpreted as the Xe–O bond, with a coordination number of about 12 consistent with Xe insertion in rings of the melt structure. Xe solubility measurements by electron microprobe and particle induced X-rays emission analysis confirm that Xe and Ar have similar solubility values in wt% in silicate melts. These values are nonetheless an order of magnitude higher than those theoretically calculated for Xe. The formation of Xe–O bonds explains the enhanced solubility of Xe in deep continental crust magmas, revealing a mechanism that could store Xe and fractionate its isotopes. Xenon is indeed atypical among noble gases, the atmosphere being notably depleted in elemental Xe, and very strongly depleted in Xe light isotopes. These observations are known as the ‘missing’ Xe paradox, and could be solved by the present findings.
Fichier principal
Vignette du fichier
Xe-Magmas_epsl-rev2.pdf (402.74 Ko) Télécharger le fichier
Origin : Files produced by the author(s)
Loading...

Dates and versions

cea-01672802 , version 1 (16-01-2018)

Identifiers

Cite

Clémence Leroy, Chrystèle Sanloup, Hélène Bureau, Burkhard C. Schmidt, Zuzana Konôpková, et al.. Bonding of xenon to oxygen in magmas at depth. Earth and Planetary Science Letters, 2017, 484, pp.103 - 110. ⟨10.1016/j.epsl.2017.12.019⟩. ⟨cea-01672802⟩
273 View
179 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More