Crustal sources in Lower Palaeozoic rocks from NW Iberia: insights from laser ablation U-Pb ages of detrital zircons

Detrital zircons from greywackes belonging to an Ordovician volcanosediment ary-igneous complex in NW Spain were dated using the laser ablation-inducti vely coupled plasma-mass spectrometry technique. U-Pb results indicate the existence of three Precambrian crustal sources in NW Iberia. The age groupi ng dated at c.590-620 Ma confirms the presence of a Cadomian-Avalonian base ment in this zone. The second age group (c. 1.1-1.2 Ga) is the first eviden ce for a Grenvillean age crustal component in NW Iberia. The age grouping d ated at c. 1.9-2.0 Ga corresponds to the age of the Icartian igneous baseme nt exposed in other areas of the European Variscides.