The Variscan metamorphic evolution of the autochthonous domain of NW and Central Iberia is characterized by a Barrovian gradient followed by a high-temperature–low-pressure (HT/LP) event associated with voluminous granite magmatism. The structural, metamorphic and magmatic histories of the region are described briefly and the relations between them are explained. A coherent model for evolution of the continental crust is proposed using published radiometric ages, thermal models and seismic reflection profiles. The metamorphic evolution, including the high-temperature event, is explained by crustal thickening resulting from the Gondwana–Laurussia collision followed by a period of thermal relaxation and a long-lasting extensional stage. The fact that the highest temperatures were reached in the core of the Central Iberian arc, partly occupied by remnants of a huge allochthonous nappe stack, is discussed in relation to both the emplacement of the allochthon and subsequent oroclinal bending. The overburden provided by the allochthonous pile was decisive in triggering the high-temperature event. Orocline development mostly occurred later and had no significant effect on the metamorphic evolution, although it was important for the present localization of gneiss domes and granitoids. The possible role of the mantle in supplying additional heat to explain the HT/LP event is also discussed. It would seem that little mantle contribution was needed and there are no strong arguments for mantle delamination, although some kind of mantle–crust interaction is expected beneath the hot regions presently occupying the core of the Central Iberian arc.

Zircon geochronology using laser ablation inductively coupled plasma mass spectrometry, combined with a new detailed geological map and a stratigraphic study of the Parautochthon at the eastern rim of the Morais Allochthonous Complex, has provided new insights into the evolution of the Iberian Variscan belt. The data confirmed that the Parautochthon is composed of two structural units. The higher and more deformed, called the Upper Parautochthon, consists of recumbently folded pre-Variscan low-grade metasediments deposited in the northern Gondwana passive margin during the opening of the Rheic Ocean. It represents the Variscan tectonic duplication of the NW Iberian autochthonous sedimentary sequence triggered by the advance of a stack of allochthonous units formed previously in an accretionary prism. Below this unit, the Lower Parautochthon is a less pervasively deformed tectonic slice including two lithostratigraphic units (Travanca and Vila Chã formations) composed of Culm-type synorogenic low-grade metasediments deposited in a tectonic trench located between the accretionary prism and a peripheral bulge, with detrital zircon age populations pointing to a Late Devonian–Early Carboniferous age. These sediments were subsequently detached from the Autochthon along mechanically weak Silurian carbonaceous slates. The provenance study on the detrital zircons implies that this basin was fed mainly from the active margin. Supplementary material: The complete U–Pb age results obtained by LA-ICP-MS analysis are available at http://www.geolsoc.org.uk/SUP18781 .