Presence of Palaeoproterozoic and Archean components in the granulite-facies rocks of central Iberia: The Hf isotopic evidence

Abstract

Hf-isotope analyses in previously dated zircon crystals from four Variscan granulite-facies rocks from
central Iberia have been studied to examine crustal evolution processes. Two samples are from exposed
migmatite terranes, the other two are granulite xenoliths from lower crustal levels. Hf model ages show
that lower crustal granulites display a bigger contribution of Archean components than exposed highgrade
rocks (14% of the zircon population instead of 6%), reinforcing ideas of preservation of ancient
crustal material in the lower crust. The distribution of age-Hf isotope data from zircon suggests two
juvenile crust formation events in central Iberia: the main one during the Neoproterozoic (540–620 Ma)
and a possible second Mesoproterozoic event around 1.0–1.2 Ga. Magmatism appears in the Central
Iberian Zone exclusively related to that younger juvenile addition. Hf data of granulite zircons agrees
with recent palaeogeographical reconstruction models which present central Iberia as a peri-Gondwanan
terrane located between the West African craton and the Arabian shield, far from the Amazonia
microplate.