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Types of metasomatism in mantle xenoliths enclosed in Neogene-Quaternary alkaline mafic lavas from Catalonia (NE Spain)

By
G. Galán
G. Galán
Departament de Geologia, Universitat Autònoma de Barcelona, Edifici C (sur), 08193 Bellaterra-Barcelona, Spain (e-mail: gumer.galan@uab.es)
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V. Oliveras
V. Oliveras
Departament de Geologia, Universitat Autònoma de Barcelona, Edifici C (sur), 08193 Bellaterra-Barcelona, Spain (e-mail: gumer.galan@uab.es)
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B. A. Paterson
B. A. Paterson
Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK
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Published:
January 01, 2008

Abstract

Mantle xenoliths in within-plate alkaline mafic lavas from NE Spain are mainly anhydrous spinel lherzolites and harzburgites, grading into each other, and subordinate pyroxenites. Peridotites followed an earlier melt depletion caused by mantle decompression and subsequent metasomatism. Two main types of metasomatism are differentiated affecting mainly the harzburgites: a silicate-melt metasomatism of Fe–Ti type and a carbonatite metasomatism. Both types are recognized in the nearby Pyrenean peridotite massifs, but the presence of hydrous minerals is less frequent in the xenoliths. The two metasomatic styles could have been generated by the intrusion of Cretaceous alkaline magmas, if a chromatographic fractionation–reaction process at decreasing melt mass took place. This would account for the evolution of the original alkaline silicate percolating melt towards a carbonatite-rich melt, allowing the coexistence in both space and time of the two metasomatic styles. Metasomatism in lherzolites could be explained in the same way. The pyroxenite xenoliths are interpreted as cumulates from these alkaline basic magmas that crop out in the area as rare camptonite dykes. Interaction with host lavas is minor and could explain the partial melting, enrichment and disequilibrium observed in a deformed composite xenolith and sporadic veins filled with glass.

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Contents

Geological Society, London, Special Publications

Metasomatism in Oceanic and Continental Lithospheric Mantle

M. Coltorti
M. Coltorti
Università degli Studi di Ferrara, Italy
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M. Grégoire
M. Grégoire
Université Toulouse III, France
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Geological Society of London
Volume
293
ISBN electronic:
9781862395411
Publication date:
January 01, 2008

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