Detrital zircons from greywackes belonging to an Ordovician volcanosedimentary-igneous complex in NW Spain were dated using the laser ablation-inductively coupled plasma-mass spectrometry technique. U–Pb results indicate the existence of three Pre-cambrian crustal sources in NW Iberia. The age grouping dated at c. 590–620 Ma confirms the presence of a Cadomian-Avalonian basement in this zone. The second age group (c. 1.1–1.2 Ga) is the first evidence for a Grenvillean age crustal component in NW Iberia. The age grouping dated at c. 1.9–2.0 Ga corresponds to the age of the Icartian igneous basement exposed in other areas of the European Variscides.