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Temporal and compositional differences between subsolidus and anatectic migmatite leucosomes from the Quetico metasedimentary belt, Canada

Sawyer Edward W. et Barnes Sarah-Jane. (1988). Temporal and compositional differences between subsolidus and anatectic migmatite leucosomes from the Quetico metasedimentary belt, Canada. Journal of Metamorphic Geology, 6, (4), p. 437-450.

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Résumé

Migmatites in the Quetico Metasedimentary Belt contain two types of leucosome: (1) Layer-parallel leucosomes that grew during deformation and prograde metamorphism. These are enriched in SiO2, Sr, and Eu, but depleted in TiO2, Fe2O3, MgO, Cs, Rb, REE, Sc, Th, Zr, and Hf relative to the Quetico metasediments. (2) Discordant leucosomes that formed after the regional folding events when metamorphic temperatures were at their peak. These are enriched in Rb, Ba, Sr and Eu, but display a wide range of LREE, Th, Zr, and Hf contents relative to the Quetico metasediments.

Layer-parallel leucosomes formed by a subsolidus process termed tectonic segregation. This stress-induced mass transfer process began when the Quetico sediments were deformed during burial, and continued whilst the rocks were both stressed and heterogeneous. Subsolidus leucosome compositions are consistent with the mobilization of quartz and feldspar from the host rocks by pressure solution. The discordant leucosomes formed by partial melting of the Quetico metasediments, possibly during uplift of the belt. The range of composition displayed by the anatectic leucosomes arises from crystal fractionation during leucosome emplacement. Some anatectic leucosomes preserve primary melt compositions and have smooth REE patterns, but those with negative Eu anomalies represent fractionated melts, and others with positive Eu anomalies represent accumulations of feldspar plus trapped melt.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:1525-1314
Volume:6
Numéro:4
Pages:p. 437-450
Version évaluée par les pairs:Oui
Date:1988
Sujets:Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Mots-clés:anatectic leucosome, Archaean, migmatite geochemistry, Quetico Metasedimentary Belt, subsolidus leucosome, Superior Province
Déposé le:10 juin 2016 12:44
Dernière modification:09 déc. 2016 16:12
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