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Age constraints to the relationships between magmatism, metamorphism and tectonism in the Aracena metamorphic belt, southern Spain Abstract The Aracena metamorphic belt (AMB), southwest Iberian peninsula, is characterized by the following geological elements: (a) a high-temperature/ low-pressure (HT/LP) metamorphic belt a few kilometres wide and more than 200 km long; (b) a linear belt of oceanic amphibolites with a low-pressure inverted metamorphic gradient; (c) crustal-scale ductile shear zones; and (d) mafic, noritic intrusions of highMg andesite (boninite) composition. The relationships between these elements led to the proposal of a model of ridge subduction for this sector of the Hercynian belt of Europe. This interpretation is supported by the age relationships displayed between the main rock units considered representative of the main tectonic and petrological processes responsible for the geological elements mentioned previously. The results of a geochronological study (Ar-Ar, Rb-Sr and Sm-Nd) clearly support a Late Paleozoic tectonic evolution at an active continental margin. The time evolution of the metamorphism in the oceanic domain, ranging from 342.6B0.6 Ma in the west to 328.4B1.2 Ma in the east, over a distance of 70 km along the metamorphic belt, support a tectonic model of triple-junction migration responsible for the creation at depth of a slab-free window with decisive consequences for the thermal evolution of the region. The origin of the linear metamorphic belt of HT/LP regime may be explained by the migration along a continental margin of a punctual thermal anomaly induced by the creation of a triplejunction at the continental margin.Key words Hercynian belt 7 Iberian massif 7 Aracena metamorphic belt 7 Migmatites 7 Norites 7 Ar ages 7 Sm-Nd 7 Rb-Sr

[1] The Aracena metamorphic belt is a hightemperature/low-pressure (HT/LP) band located at the southern end of the European Variscan chain. It marks a suture between Armorica and Avalonia. This belt is characterized by (1) the presence of mid-ocean ridge basalt-derived metabasites that were affected by an inverted HT/LP metamorphism related to SW verging thrusting, whose thermal peak diachronously migrated eastward; (2) the occurrence of a HT/LP metamorphism, related to an extensional event, affecting continental rocks belonging to the Ossa Morena zone with peak temperatures that are $150°C higher than that recorded in the oceanic metabasites; and (3) the presence of near-trench magmatism with high-Mg andesite composition. These and other characteristics can be interpreted in terms of a ridgetrench-trench triple junction that migrated along the Armorican margin during Variscan oblique convergence. Citation: Díaz Azpiroz, M., C. Fernández, A. Castro, and M. El-Biad (2006), Tectonometamorphic evolution of the Aracena metamorphic belt (SW Spain) resulting from ridgetrench interaction during Variscan plate convergence, Tectonics, 25, TC1001,