Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain

In situ uranium-lead dating (LA-SF-ICPMS and SIMS) and Lu-Hf isotope analyses (LA-MC-ICP-MS) of zircon from eclogite facies rocks from the basal units of the Variscan Belt in Galicia constrain their magmatic and metamorphic evolution and give some clues about the nature and origin of the involved ba...

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Autores: Abati Gómez, Jacobo, Gerdes, Axel, Fernández Suárez, Javier, Arenas Martín, Ricardo, Whitehouse, Martín J., Díez Fernández, Rubén
Tipo de recurso: artículo
Fecha de publicación:2010
País:España
Institución:Universidad Complutense de Madrid (UCM)
Repositorio:Docta Complutense
Idioma:inglés
OAI Identifier:oai:docta.ucm.es:20.500.14352/44356
Acceso en línea:https://hdl.handle.net/20.500.14352/44356
Access Level:acceso abierto
Palabra clave:552.3(460.11)
Magmatism
Variscan
Gondwana margin
Galicia
NW Spain
Petrología
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spelling Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain Abati Gómez, Jacobo Gerdes, Axel Fernández Suárez, Javier Arenas Martín, Ricardo Whitehouse, Martín J. Díez Fernández, Rubén 552.3(460.11) Magmatism Variscan Gondwana margin Galicia NW Spain Petrología In situ uranium-lead dating (LA-SF-ICPMS and SIMS) and Lu-Hf isotope analyses (LA-MC-ICP-MS) of zircon from eclogite facies rocks from the basal units of the Variscan Belt in Galicia constrain their magmatic and metamorphic evolution and give some clues about the nature and origin of the involved basement. The samples studied are two felsic gneisses, two eclogites, and one eclogitic gneiss of intermediate composition (metatonalite). Oscillatory-zoned zircon cores from the felsic samples gave a main clustering of U-Pb ages at 493 ± 2 and 494 ± 2 Ma, and some older ages that represent inherited cores. Zircon grains from the intermediate and one of the mafic rocks show no inherited cores and yielded ages of 494 ± 3 and 498 ± 6 Ma, respectively, interpreted as time of protolith crystallization. Variably developed homogeneous zircon rims in one felsic gneiss yielded an age of 372 ± 3 Ma, and very tiny zircons of one eclogite gave 350 ± 2 Ma, both of which we interpret as metamorphic ages. The new age data demonstrate that the calc-alkaline magmatic suite described in the basal unit is ca. 20 Ma older than the alkaline to peralkaline plutonic suite of the same unit (dated at 472 ± 2 Ma; Rodríguez et al., 2007), and thus probably represents a distinct geologic event. Overgrowth rims are interpreted as metamorphic on the basis of their Lu/Hf and Th/U ratios. The 372 ± 3 age is considered as dating the high-pressure (high-P) metamorphism, and is essentially in agreement with previous Ar-Ar and Rb-Sr data. This high-P metamorphism marks the initial early-Variscan subduction of the Gondwana margin. The inherited zircon ages and Hf isotopic composition of zircons point to a considerable input of crustal material with West African Craton provenance to the felsic magma. Geological Society of America https://hdl.handle.net/20.500.14352/44356
title Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
spellingShingle Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
Abati Gómez, Jacobo
552.3(460.11)
Magmatism
Variscan
Gondwana margin
Galicia
NW Spain
Petrología
title_short Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
title_full Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
title_fullStr Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
title_full_unstemmed Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
title_sort Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
author Abati Gómez, Jacobo
author_facet Abati Gómez, Jacobo
Gerdes, Axel
Fernández Suárez, Javier
Arenas Martín, Ricardo
Whitehouse, Martín J.
Díez Fernández, Rubén
author_role author
author2 Gerdes, Axel
Fernández Suárez, Javier
Arenas Martín, Ricardo
Whitehouse, Martín J.
Díez Fernández, Rubén
author2_role author
author
author
author
author
topic 552.3(460.11)
Magmatism
Variscan
Gondwana margin
Galicia
NW Spain
Petrología
topic_facet 552.3(460.11)
Magmatism
Variscan
Gondwana margin
Galicia
NW Spain
Petrología
description In situ uranium-lead dating (LA-SF-ICPMS and SIMS) and Lu-Hf isotope analyses (LA-MC-ICP-MS) of zircon from eclogite facies rocks from the basal units of the Variscan Belt in Galicia constrain their magmatic and metamorphic evolution and give some clues about the nature and origin of the involved basement. The samples studied are two felsic gneisses, two eclogites, and one eclogitic gneiss of intermediate composition (metatonalite). Oscillatory-zoned zircon cores from the felsic samples gave a main clustering of U-Pb ages at 493 ± 2 and 494 ± 2 Ma, and some older ages that represent inherited cores. Zircon grains from the intermediate and one of the mafic rocks show no inherited cores and yielded ages of 494 ± 3 and 498 ± 6 Ma, respectively, interpreted as time of protolith crystallization. Variably developed homogeneous zircon rims in one felsic gneiss yielded an age of 372 ± 3 Ma, and very tiny zircons of one eclogite gave 350 ± 2 Ma, both of which we interpret as metamorphic ages. The new age data demonstrate that the calc-alkaline magmatic suite described in the basal unit is ca. 20 Ma older than the alkaline to peralkaline plutonic suite of the same unit (dated at 472 ± 2 Ma; Rodríguez et al., 2007), and thus probably represents a distinct geologic event. Overgrowth rims are interpreted as metamorphic on the basis of their Lu/Hf and Th/U ratios. The 372 ± 3 age is considered as dating the high-pressure (high-P) metamorphism, and is essentially in agreement with previous Ar-Ar and Rb-Sr data. This high-P metamorphism marks the initial early-Variscan subduction of the Gondwana margin. The inherited zircon ages and Hf isotopic composition of zircons point to a considerable input of crustal material with West African Craton provenance to the felsic magma.
publishDate 2010
format article
url https://hdl.handle.net/20.500.14352/44356
language eng
eu_rights_str_mv openAccess
publisher Geological Society of America
institution Universidad Complutense de Madrid (UCM)
collection Docta Complutense
reponame_str Docta Complutense
instname_str Universidad Complutense de Madrid (UCM)
_version_ 1878442813584048128
publishDateSort 2010
author_browse Abati Gómez, Jacobo
Arenas Martín, Ricardo
Díez Fernández, Rubén
Fernández Suárez, Javier
Gerdes, Axel
Whitehouse, Martín J.
publisherStr Geological Society of America
score 6.9303427

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