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A Quartz-bearing Orthopyroxene-rich Websterite Xenolith from the Pannonian Basin, Western Hungary: Evidence for Release of Quartz-saturated Melts from a Subducted Slab

Bali, E. ; Zajacz, Z. ; Kovács, I. ; Szabó, CS ; Halter, W. ; Vaselli, O. ; Török, K. ; Bodnar, R. J.

In: Journal of Petrology, 2008, vol. 49, no. 3, p. 421-439

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    Titre
    • A Quartz-bearing Orthopyroxene-rich Websterite Xenolith from the Pannonian Basin, Western Hungary: Evidence for Release of Quartz-saturated Melts from a Subducted Slab
    Auteur
    • Bali, E.. lithosphere Fluid Research Lab, Department of Petrology & Geochemistry, Institute of Geography and Earth Sciences, Eötvös University Budapest (ELTE), Pazmany Setany 1/c, Budapest, H-1117, Hungary
    • Zajacz, Z.. lithosphere Fluid Research Lab, Department of Petrology & Geochemistry, Institute of Geography and Earth Sciences, Eötvös University Budapest (ELTE), Pazmany Setany 1/c, Budapest, H-1117, Hungary
    • Kovács, I.. lithosphere Fluid Research Lab, Department of Petrology & Geochemistry, Institute of Geography and Earth Sciences, Eötvös University Budapest (ELTE), Pazmany Setany 1/c, Budapest, H-1117, Hungary
    • Szabó, CS. lithosphere Fluid Research Lab, Department of Petrology & Geochemistry, Institute of Geography and Earth Sciences, Eötvös University Budapest (ELTE), Pazmany Setany 1/c, Budapest, H-1117, Hungary
    • Halter, W.. Institute of Isotope Geochemistry and Mineral Resources, ETH Zürich, Sonneggstrasse 5, ETH Zentrum, 8092 Zürich, Switzerland
    • Vaselli, O.. Department of Earth Sciences, University of Florence, Via G. LA Pira, 4, Florence, 50121, Italy
    • Török, K.. lithosphere Fluid Research Lab, Department of Petrology & Geochemistry, Institute of Geography and Earth Sciences, Eötvös University Budapest (ELTE), Pazmany Setany 1/c, Budapest, H-1117, Hungary
    • Bodnar, R. J.. Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Journal of Petrology, 2008, vol. 49, no. 3, p. 421-439. Oxford University Press
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:293299
    Summary
    An unusual quartz-bearing orthopyroxene-rich websterite xenolith has been found in an alkali basaltic tuff at Szigliget, Bakony-Balaton Highland Volcanic Field (BBHVF), western Hungary. Ortho- and clinopyroxenes are enriched in light rare earth elements (LREE), middle REE and Ni, and depleted in Nb, Ta, Sr and Ti compared with ortho- and clinopyroxenes occurring in either peridotite or lower crustal granulite xenoliths from the BBHVF. Both ortho- and clinopyroxenes in the xenolith contain primary and secondary silicate melt inclusions, and needle-shaped or rounded quartz inclusions. The melt inclusions are rich in SiO2 and alkalis and poor in MgO, FeO and CaO. They are strongly enriched in LREE and large ion lithophile elements, and display negative Nb, Ta and Sr anomalies, and slightly positive Pb anomalies. The xenolith is interpreted to represent a fragment of an orthopyroxene-rich body that crystallized in the upper mantle from a hybrid melt that formed by interaction of mantle peridotite with a quartz-saturated silicate melt that was released from a subducted oceanic slab. Although the exact composition of the slab melt cannot be determined, model calculations on major and trace elements suggest involvement of a metasedimentary component