SHRIMP U–Pb zircon dating of anatexis in high-grade migmatite complexes of Central Spain: implications in the Hercynian evolution of Central Iberia

Abstract

U-Pb SHRIMP ages obtained in zircons from the Sotosalbos and Toledo anatectic complexes in Central Spain give new constraints to the evolution of the inner part of the Hercynian Iberian belt. Pre Hercynian ages in zircons from the Sotosalbos com plex (-464 Ma) are well preserved and reveal that an age diversity of the Lower Paleozoic magmatism in the area exists, as previous data on westernmost or thogneisses yield significant older ages. Zircon ages in the pelite-derived granites from the Toledo complex also show an important N eoproterozoic age compo nent which points to a metasedimentary protolith deposited maximally 560 Ma ago. Younger zircon populations in both complexes at -330 Ma in the Sotosalbos region and -317 Ma in the Toledo com plex indicate an important diachronism between the anatectic processes in both areas but also that these processes are mainly unrelated to the generation of the later Hercynian granite batholith of Central Spain, which could be of deeper crustal derivation. In addition, as migmatization occurred late in the metamorphic cycle, after peak conditions were at tained, the age of anatexis is younger than the age of the main Hercynian metamorphic event, which still is not well constrained.

U–Pb and 39Ar/40Ar data constraining the ages of the source, emplacement and recrystallization/cooling events from late- to post-D3 Variscan granites of the Gouveia area, central Portugal

“…This would accord with the permanent location of Iberia at the northern margin of Gondwana throughout the Paleozoic (Martínez Catalán et al, 2004). The Amazonian Craton could be a potential source area for the Neoproterozoic and Paleozoic sediments of the Variscan belt (Castiñeiras et al, 2008;Fernández-Suárez et al, 2000Gutiérrez-Alonso et al, 2003), but there is an absence of Mesoproterozoic zircon. In European Variscan terranes, sediments from the Amazonian craton generally contain Mesoproterozoic detrital zircon (e.g.…”

“…Detrital zircons from some Portuguese metasediments in the CIZ are mainly of Neoproterozoic age (Teixeira et al, 2011). The pelite-derived granites from the Toledo complex in the CIZ also contain a significant inherited zircon component of Neoproterozoic age (Castiñeiras et al, 2008).…”

Anomalous xenocryst dispersion during tonalite–granodiorite crystal mush hybridization in the mid crust: Mineralogical and geochemical evidence from Variscan appinites (Avila Batholith, Central Iberia)

“…In the Toledo anatectic complex, migmatization ages are more restricted. Castiñeiras et al (2008) detected a main migmatization phase at ca. 317 Ma and other episodes at ca.…”

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

“…U-Pb zircon dating in orthogneisses has yielded crystallisation ages from 496 to 464 Ma (Castifieiras et al, 2008;Montero et al, 2009;Valverde-Vaquero and Dunning, 2000;Zeck et al, 2007a). The presence of Ordovician ages in zircon grains from SCS 1-type granites suggests that their source materials could be Ordovician plutonic rocks metamorphosed during the Variscan collision at lower crustal levels (Orejana et al, 2012).…”

“…Peak low P/high temperature metamorphism is constrained at about 330 Ma (Castifieiras et al, 2008;Escuder-Viruete et al, 1998;Montero et al, 2004). The high-grade gneisses have provided Ar-Ar muscovite and K-Ar biotite ages of 314-310 Ma (Valverde Vaquero et al, 2007), which reflect cooling below 350 cc.…”