Tracing crustal evolution in the NW Iberian Peninsula through the Rb---Sr and U---Pb systematics of Palaeozoic granitoids: a review

Abstract

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 Namurian), ~ 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.