Coupled U–Pb geochronology of inherited and detrital zircon in the Iberian Massif: insights into its deep structure and geodynamic evolution

Abstract

Abstract The combined use of detrital and inherited zircon U-Pb age spectra provides new insights into the crustal evolution of the Iberian Massif as part of the North Gondwana margin. In the Ossa–Morena Zone (OMZ), Ediacaran detrital zircon populations are dominated by Pan‑African ages, whereas inherited zircons overwhelmingly record Cadomian signatures, implying that Cadomian crust remained largely unexposed during the Cadomian event itself. Late-Rift igneous units of the Central Iberian Zone (CIZ) and Galicia-Trás-os-Montes Zone (GTMZ) Parautochthon present significant inherited Cambrian signals, indicating a shared cryptic infracrustal magmatism which is extensively exposed in OMZ (Early Rift and Main Rift events). Carboniferous zircon records reveal sharp contrasts. OMZ Carboniferous detrital zircon patterns reflect syn-sedimentary magmatism and active erosion of Famennian-Tournaisian igneous bodies. There is a notable lack of zircons from older magmatic sources, implying limited exposure of Cambrian and Ediacaran basement during Carboniferous basin formation. Inherited zircons from OMZ Carboniferous rocks display typical Cadomian–Pan-African and Cambrian peaks, but also unexpected signals from South Portuguese Zone (SPZ) magmatism, suggesting deep mixing of OMZ–SPZ sources. In contrast, CIZ Carboniferous sediments are dominated by Precambrian sources, showing weak Variscan signals, even though inherited zircons reveal clear signatures of Cadomian–Pan‑African, Rift‑to‑Drift, and Variscan events. Because detrital zircon spectra are strongly influenced by crustal exposure, inherited zircon patterns provide a more robust record of deep crustal processes and allow a more precise determination of the climax ages of major orogenic events in the Iberian Massif.