U-Pb geochronology and zircon composition of late Variscan S- and I-type granitoids from the Spanish Central System batholith
Date
2012
Authors
Orejana, David
Villaseca, Carlos
Valverde-Vaquero, Pablo
Belousova, Elena
Armstrong, Richard
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Springer
Abstract
The Spanish Central System (SCS) batholith, located in the Central Iberian Zone, is one of the largest masses of granite in the European Variscan Belt. This batholith is a composite unit of late- and post-kinematic granitoids dominated by S- and I-type series granite, with subordinate leucogranite and granodiorite. Zircon trace element contents, from two representative S-type and three I-type granitoids from the eastern portion of the SCS batholith, indicate a heterogeneous composition due to magma differentiation and co-crystallisation of other trace element-rich accessory phases. In situ, U-Pb dating of these zircons by SHRIMP and LA-ICP-MS shows 479-462-Ma inherited zircon ages in the I-type intrusions, indicating the involvement of an Ordovician metaigneous protolith, while the S-type intrusions exclusively contain Cadomian and older zircon ages. The zircon crystallisation ages show that these granites have been emplaced at ca. 300 Ma with a time span between 303 ± 3 Ma and 298 ± 3 Ma. Precise dating by CA-ID-TIMS reveals a pulse at 305. 7 ± 0. 4 Ma and confirms the major pulse at 300. 7 ± 0. 6 Ma. These ages match the Permo-Carboniferous age for granulite-facies metamorphism of the lower crust under the SCS batholith and coincide with a widespread granitic event throughout the Southern Variscides. Ti-in zircon thermometry indicates temperatures between 844 and 784°C for both the S- and I-type granites, reinforcing the hypothesis that these granites are derived from deep crustal sources.
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Keywords
Keywords: batholith; emplacement; geochronology; granitoid; granodiorite; granulite facies; Hercynian orogeny; I-type rock; igneous intrusion; leucogranite; metaigneous rock; metamorphism; protolith; S-type rock; trace element; uranium-lead dating; zircon; Sistema European Variscan Belt; Peraluminous granites; Spanish Central System; U-Pb zircon dating
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Source
International Journal of Earth Sciences (Geologische Rundschau)
Type
Journal article
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2037-12-31
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