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Lower-mantle water reservoir implied by the extreme stability of a hydrous aluminosilicate

Titelangaben

Pamato, Martha Giovanna ; Myhill, Robert ; Boffa Ballaran, Tiziana ; Frost, Daniel J. ; Heidelbach, Florian ; Miyajima, Nobuyoshi:
Lower-mantle water reservoir implied by the extreme stability of a hydrous aluminosilicate.
In: Nature Geoscience. Bd. 8 (Januar 2015) Heft 1 . - S. 75-79.
ISSN 1752-0908
DOI: 10.1038/ngeo2306

Abstract

The source rocks for basaltic lavas that form ocean islands are often inferred to have risen as part of a thermal plume from the lower mantle. These rocks are water-rich compared with average upper-mantle rocks. However, experiments indicate that the solubility of water in the dominant lower-mantle phases is very low, prompting suggestions that plumes may be sourced from as-yet unidentified reservoirs of water-rich primordial material in the deep mantle. Here we perform high-pressure experiments to show that Al2SiO4(OH)2[mdash]the aluminium-rich endmember of dense, hydrous magnesium silicate phase D[mdash]is stable at temperatures extending to over 2,000 [deg]C at 26 GPa. We find that under these conditions, Al-rich phase D is stable within mafic rocks, which implies that subducted oceanic crust could be a significant long-term water reservoir in the convecting lower mantle. We suggest that melts formed in the lower mantle by the dehydration of hydrous minerals in dense ultramafic rocks will migrate into mafic lithologies and crystallize to form Al-rich phase D. When mantle rocks upwell, water will be locally redistributed into nominally anhydrous minerals. This upwelling material provides a potential source for ocean-island basalts without requiring reservoirs of water-rich primordial material in the deep mantle.

Weitere Angaben

Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Institutionen der Universität: Profilfelder > Advanced Fields > Hochdruck- und Hochtemperaturforschung
Forschungseinrichtungen > Forschungszentren > Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik - BGI
Profilfelder
Profilfelder > Advanced Fields
Forschungseinrichtungen
Forschungseinrichtungen > Forschungszentren
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
Eingestellt am: 19 Mai 2017 08:35
Letzte Änderung: 06 Jun 2017 08:29
URI: https://eref.uni-bayreuth.de/id/eprint/37170