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The abundant granitoids in the Palaeozoic basement of the northwestern Iberian Peninsula include 470-440 Ma old suites (Early-Middle Ordovician, now present as orthogneisses) and several Variscan suites. The age data presently available suggest that the latter have been generated in three separate time intervals,-330-320 Ma ago (Late Visean-Early Namunan),-310-300 Ma ago (Westphalian) and-290-280 Ma ago (Late Stephanian-Autunian). Rb-Sr whole-rock and U-Pb zircon systematics, along with field and chemical evidence, testify to the generation of the Early and Late Palaeozoic granitoids from Lower Palaeozoic and Precambrian (maximum age-1.7-1.6 Ga) sedimentary sequences, respectively. The source rocks contained zircons derived from a late Archaean-Early Proterozoic continental crust that probably underlies the whole of western Europe, although for the greater part modified beyond recognition by younger crustal reworking.

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