Abstract 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.

The innermost domain of the autochthon of the Iberian Massif (Central Iberian Zone) consists of Upper Proterozoic–Lower Cambrian metasedimentary rocks and Early Paleozoic augen gneisses. The former were intruded by mafic magmas as small bodies that later became amphibolites under Variscan metamorphism, gabbro-diabasic textures being sometimes well preserved. Three main groups of amphibolites can be established: (A) the light rare earth element (LREE)-depleted group, characterized by an extremely low rare earth element (REE) fractionation factor [(La/Lu) CN = 0.27–0.34] and low Ti content; (B) the flat REE pattern group, characterized by a small REE fractionation factor [(La/Lu) CN small REE fractionation factor [(La/Lu) CN = 0.95–1.25]; and (C) the LREE-enriched group, characterized by a strong fractionation factor [(La/Lu) CN = 3.53–15.04] and high Ti content. Regular major element variations for the depleted amphibolites point to a low-pressure fractional crystallization as the major process, the strongly depleted amphibolites considered to be parent magmas, although crustal contamination accounts for their broad Nd and Sr isotope ranges as well as trace element variations. Part of the enriched amphibolite samples have an ocean island basalt–like signature and plot within the mantle array, suggesting a mantle mixed source. Other samples show decoupling of Nd and Sr isotopic systems as a response to a probable mixing process involving fluid-rock interaction during subsolidus evolution, which is supported by their high δ 18 O values. Geochemical characterization of amphibolite groups is consistent with an extensional within-plate tectonic setting, whereas processes involved may account for a similar mantle-crust interaction that occurred throughout the entire Central Iberian Zone and probably all over the northern margin of Gondwana during late Neoproterozoic–Early Paleozoic times.