Accéder directement au contenu Accéder directement à la navigation
Article dans une revue

Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration

Abstract : The structural hydroxyl content of the nominally anhydrous minerals (olivine and pyroxenes) in the upper mantle is among the important attributes that influence the physical and chemical features of the upper mantle. In this study, we provide detailed Fourier-transform infrared (FTIR) data on 63 petrographically and geochemically well-defined upper mantle xenoliths from the Nograd-Gomor Volcanic Field (Pannonian Basin, Central Europe). These xenoliths show extremely low average structural hydroxyl contents (similar to 0, 31 and 185 ppm for olivine, orthopyroxene and clinopyroxene, respectively) compared to values reported regionally and worldwide. The studied xenoliths have anomalous types of FTIR spectra and high structural hydroxyl ratios between clinopyroxenes and orthopyroxenes (an average of similar to 8). Furthermore, there is usually no correlation between the structural hydroxyl content and other physical or chemical properties of the xenoliths. These specific FTIR characteristics suggest that the Nograd-Gomor upper mantle xenoliths were exposed to significant modification of their structural hydroxyl contents, which may be linked to pre- and post-eruptive processes. Decompression during extension leads to lower 'water' activity, which is most likely to have played a key role. However, pre-eruptive mantle metasomatism with an agent having low water activity cannot be excluded either. The post-eruptive cooling can be significant as well, as suggested by the higher structural hydroxyl content in xenoliths hosted in more rapidly cooled volcanic facies (i.e. pyroclastics). Our study reveals how FTIR characteristics may evolve in continental rift settings in young extensional basins. Furthermore, novel applications of our study are the diagnostic features that indicate significant changes in structural hydroxyl properties. This contributes to distinguishing low structural hydroxyl contents linked to the pre-eruptive (i.e., low structural hydroxyl content in pyroxenes, anomalous partitioning and anomalous band characteristic in pyroxenes) or the post-eruptive (completely 'dry' olivines) periods.
Liste complète des métadonnées

Littérature citée [125 références]  Voir  Masquer  Télécharger

https://hal.univ-lille.fr/hal-02313678
Contributeur : Lilloa Université de Lille <>
Soumis le : vendredi 11 octobre 2019 - 14:32:23
Dernière modification le : mercredi 27 mai 2020 - 03:20:17

Fichier

1-s2.0-S0009254118306028-main....
Fichiers éditeurs autorisés sur une archive ouverte

Licence


Distributed under a Creative Commons Paternité - Pas d'utilisation commerciale - Pas de modification 4.0 International License

Identifiants

Collections

Citation

Levente Patkó, Nóra Liptai, István János Kovács, László El Aradi, Qun-Ke Xia, et al.. Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration. Chemical Geology, Elsevier, 2019, Chemical Geology, 507, pp.23-41. ⟨10.1016/j.chemgeo.2018.12.017⟩. ⟨hal-02313678⟩

Partager

Métriques

Consultations de la notice

63

Téléchargements de fichiers

143