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U–Pb geochronology and zircon composition of late Variscan S- and I-type granitoids from the Spanish Central System batholith

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Orejana García, David and Villaseca González, Carlos and Valverde Vaquero, Pablo and Belousova, Elena and Armstrong, Richard A. (2012) U–Pb geochronology and zircon composition of late Variscan S- and I-type granitoids from the Spanish Central System batholith. Geologische Rundschau, 101 . pp. 1789-1815. ISSN 0016-7835

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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 784C for both the S- and I-type granites, reinforcing
the hypothesis that these granites are derived from
deep crustal sources.


Item Type:Article
Uncontrolled Keywords:U–Pb zircon dating, Peraluminous granites, Spanish Central System, European Variscan Belt
Subjects:Sciences > Geology > Petrology
ID Code:22223
Deposited On:08 Jul 2013 09:11
Last Modified:08 Jul 2013 09:11

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