Syn-deformation fluid-assisted growth of monazite during renewed high-grade metamorphism in metapelites of the Central Rhodope (Bulgaria, Greece)

Détails

ID Serval
serval:BIB_A4F043737221
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Syn-deformation fluid-assisted growth of monazite during renewed high-grade metamorphism in metapelites of the Central Rhodope (Bulgaria, Greece)
Périodique
Chemical Geology
Auteur(s)
Didier A., Bosse V., Cherneva Z., Gautier P., Georgieva M., Paquette J.L., Gerdjikov I.
ISSN
0009-2541
Statut éditorial
Publié
Date de publication
2014
Peer-reviewed
Oui
Volume
381
Pages
206-222
Langue
anglais
Résumé
We present textural, chemical and U-Th-Pb-age data on monazites from garnet-kyanite (Grt-Ky) metapelites, from the Chepelare Shear Zone (Bulgaria) and the Nestos Shear Zone (Greece), in the Central Rhodope. Samples from both locations have experienced two stages of high temperature metamorphism during Alpine times. The first event involved mid-Mesozoic granulite facies dehydration melting. The second event involved mid- Cenozoic lower-grade fluid-assisted partial melting. The latter is well expressed in adjacent felsic rocks but had
limited impact on the Grt-Ky metapelites. Most samples display evidence for strong ductile shearing in the presence of fluids.Monazite is present in the highly foliated matrix and as inclusions in garnet and kyanite. Unlike the inclusions, matrix monazites display features of fluid-assisted dissolution-recrystallization. Y-poor domains with U-Th-Pb ages of between ca. 115 and 165 Ma represent the largest part of the grains. Y-rich domains with mid-Cenozoic ages occur as rims, or as small satellite grains surrounding the Mesozoic grains. The Cenozoic monazite domains crystallized at the expense of the Mesozoic ones and simultaneously incorporated Y provided by the fluid-assisted resorption of garnet. An age of ca. 36Ma is obtained for the samples of both shear zones, interpreted as dating the main episode of monazite growth during the Cenozoic. Similar ages exist for the crystallization of leucosomes and pegmatites in the adjacent migmatitic gneisses, indicating that the fluids responsible for the precipitation of the Cenozoic monaziteswere probably released during the crystallization of nearby anatectic melts. Together with associated rutile and biotite, many newly grown monazites show a preferred orientation paralleling the matrix foliation. This supports the hypothesis of dynamic dissolution-precipitation as an efficient mean to promote renewed monazite crystallization during ductile deformation of the host rock at ca. 36 Ma.
Mots-clé
Monazite, In situ dating, U-Th-Pb geochronology, LA-ICP-MS, Rhodope, Polycyclic metamorphism
Création de la notice
11/06/2014 16:03
Dernière modification de la notice
03/03/2018 20:14
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