Nature and evolution of the lower crust under central Spain: Inferences from granulite xenoliths (Calatrava Volcanic Field-Spanish central system)

So far, the nature and evolution of the lower crust under central Spain have been constrained mainly on the basis of a heterogeneous suite of granulite xenoliths from the Spanish Central System (SCS). In recent years, ultramafic volcanics from the Calatrava Volcanic Field (CVF) have also provided deep-seated crustal xenoliths which have not been studied in detail. Our data, combining mineral, whole-rock and isotopic geochemistry with U-Pb-Hf isotope ratios in zircons from the CVF and SCS xenoliths, highlight the felsic composition of the lower crust under central Iberia. A number of the Calatrava xenoliths represents Variscan igneous protoliths, which are a minor population in the SCS, and were likely formed by crystalli-sation of intermediate and felsic melts in the lower crust during the Variscan orogeny (leucodiorite pro-tolith age of 314 +/- 3 Ma and leucogranite protolith age of 308 +/- 2.5 Ma). U-Pb data of metamorphic zircons show that granulite-facies metamorphism mainly occurred from 299 to 285 Ma in both areas. These ages are slightly younger than those of granitic intrusions that could be genetically related to the granulitic residue, which points to a main role of U-Pb isotope resetting in lower crustal zircons dur-ing HT or UHT conditions. The zircon U-Pb-Hf isotopic ratios support the idea that the lower crust in cen-tral Iberia consists mainly of Ordovician-Neoproterozoic metaigneous and metasedimentary rocks associated with the Cadomian continental arc of northern Gondwana. These rocks provide evidence of mixing between juvenile magmas and an enriched crustal component, ultimately extracted from an Eburnean crust. Other more evolved components present in detrital zircons are likely related to recycling of Archean crust derived from North Africa cratonic terranes.(c) 2022 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Automated summary

The lower crust under central Spain consists mainly of Ordovician-Neoproterozoic metaigneous and metasedimentary rocks, mixed with juvenile magmas and an enriched crustal component. The findings provide important insights into crustal evolution and tectonic background.