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Recycled metaigneous crustal sources for S- and I-type Variscan granitoids from the Spanish Central System batholith: Constraints from Hf isotope zircon composition

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Villaseca González, Carlos and Orejana García, David and Belousova, Elena (2012) Recycled metaigneous crustal sources for S- and I-type Variscan granitoids from the Spanish Central System batholith: Constraints from Hf isotope zircon composition. Lithos (Oslo. Print), 153 . pp. 84-93. ISSN 0024-4937

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Official URL: http://www.journals.elsevier.com/lithos/



Abstract

The Spanish Central System (SCS) is one of the largest granite batholiths in the European Variscan Belt.
Zircons from five granitic intrusions from the eastern SCS have been separated and analysed for Hf isotopes
by laser ablation MC-ICPMS, in order to evaluate the nature of granitic magma source. Two samples are
cordierite-bearing S-type granites, the rest are amphibole-bearing I-type monzogranites. Hf-isotope
composition of zircons from these granites defines a narrow range of negative ɛHf values (−1.1 to −5.8),
typical of crustal protoliths. The within-sample variation of zircon Hf isotope composition is slightly above
the analytical uncertainty (±1.5 ɛ units), suggesting the mixing of different magma batches during pluton
assembly. The S- and I-type granites display the same range of initial ɛHf values, that is in agreement with
previous data showing that both SCS granite types have similar (Sr, Nd, O, Pb) isotope signatures. These
isotopic data suggest that they derived from similar sources, while the variation in peraluminosity could be
related to different partial melting conditions.
The presence of a Lower Ordovician inherited zircon population (478–462 Ma), at least in I-type granites,
suggests the involvement of Cambro–Ordovician orthogneisses as components in the source of some SCS
granites. Inherited zircon population of similar age has also been identified in the SCS lower crustal
granulites. The Hf-isotope composition of the analysed granite zircons is within that of zircons from the
above granulites. Moreover, some evidence of a juvenile input at 560–595 Ma is recorded by Hf-isotope data
in zircons from both the SCS granites and granulite xenoliths. Hf-isotope signature, in conjunction with other
chemical, isotopic (Sr, Nd, O, Pb) and geochronological evidences, suggests that SCS granites were probably
derived from metaigneous lower crustal sources. The Variscan magmatism in central Spain is dominantly a
crustal reworking event.


Item Type:Article
Uncontrolled Keywords:U–Pb dating,Zircon Hf-isotope composition, Peraluminous granites, Spanish Central System, Variscan Iberian Belt
Subjects:Sciences > Geology > Petrology
ID Code:22257
Deposited On:08 Jul 2013 09:34
Last Modified:11 Mar 2014 00:30

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