IBERSEIS, a 303 km long (20 s) deep seismic reflection profile, was acquired across the Variscan belt in SW Iberian Peninsula. The acquisition parameters were designed to obtain a high‐resolution crustal‐scale image of this orogen. The seismic profile samples three major tectonic terranes: the South Portuguese Zone, the Ossa‐Morena Zone, and the Central Iberian Zone, which were accreted in Late Paleozoic times. These terranes show a distinctive seismic signature, as do the sutures separating them. Late strike‐slip movements through crustal wedges are apparent in the seismic image and have strongly modified the geometry of sutures. The upper crust appears to be decoupled from the lower crust all along the seismic line, but some deformation has been accommodated at deeper levels. A sill‐like structure is imaged in the middle crust as a 1–2 s thick and 175 km long high‐amplitude conspicuous reflective band. It is interpreted as a great intrusion of mafic magma in a midcrustal decollement. Taking into account surface geological data and the revealed crustal architecture, a tectonic evolution is proposed for SW Iberia which includes transpressional collision interacting during Early Carboniferous with a mantle plume. The Moho can be identified along the entire transect as subhorizontal and located at 10 to 11 s, indicating a 30–35 km average crustal thickness. Its seismic signature changes laterally, being very reflective beneath the South Portuguese Zone and the Central Iberian Zone, but discontinuous and diffuse below the Ossa Morena Zone.

The Rheic Ocean was a major oceanic domain between Avalonia and Gondwana in Ordovician‐Silurian times. Most of the Paleozoic plate reconstructions assume that the Rheic Ocean suture lies within southern Iberia, coinciding with the contact between the South Portuguese Zone and the Ossa‐Morena Zone. This paper reports four Sensitive High Resolution Ion Micro‐Probe (SHRIMP) U‐Pb zircon ages from mid‐ocean ridge basalt (MORB)‐featured rocks of the Beja‐Acebuches Amphibolite unit, which crops out along the boundary between the Ossa‐Morena and the South Portuguese Zone, and is considered its most conspicuous suture unit. The obtained ages range from 332 ± 3 to 340 ± 4 Ma, corresponding to the crystallization of the mafic protoliths. These Early Carboniferous ages for the Beja‐Acebuches amphibolites imply that this unit can no longer be viewed as an ophiolite belonging to the Rheic Ocean suture, since this oceanic domain was presumably closed in Devonian times. Tectonic reconstructions joining in a single suture line the Beja‐Acebuches Amphibolite unit in southern Iberia to either the Devonian Lizard ophiolite in southern England or the root zone of the Devonian/Ordovician ophiolitic units in northwest Iberia must be therefore reconsidered because of the age difference. We interpret the Beja‐Acebuches Amphibolite unit to represent a narrow and very ephemeral realm of oceanic‐like crust that opened in Early Carboniferous times, after total consumption of the Rheic Ocean. We suggest that a mantle plume underneath southern Iberia in Early Carboniferous times is the most plausible large‐scale geodynamic scenario for the formation of these MORB‐featured rocks.

Three tectonometamorphic units can be differentiated in the boundary between the Central Iberian and Ossa‐Morena zones of the Iberian Massif (Variscan belt). The three units have been named the Northern Unit, Central Unit, and Southern Unit. The Northern Unit corresponds to the border of the Central Iberian Zone; it evolved at low‐temperature and intermediate‐ or low‐pressure metamorphic conditions and was affected by top to the SE ductile shearing. The Central Unit, placed under the Northern Unit, preserves high‐pressure Silurian eclogitic assemblages retrograded by high‐ to medium‐temperature and, finally, low‐temperature ductile shearing with top to the NW sense of movement (oblique left‐lateral). The Central Unit is superposed on the Southern Unit. The latter corresponds to the border of the Ossa‐Morena Zone and underwent low‐pressure, intermediate‐temperature metamorphism synchronous with right‐lateral (top to the SE) ductile shearing. The envisaged tectonic evolution is as follows: after a stage of lower Paleozoic rifting, subduction of the Central Unit under the Northern Unit took place in Silurian times. As a result of the crustal thickening, a gravitational instability developed, giving way to left‐lateral extensional shearing that affected the entire Central Unit. The combined action of oblique thrusting at the front of the wedge and oblique extensional shearing at the rear caused the exhumation of the high‐pressure rocks of the Central Unit. This tectonic evolution reveals that the boundary between the Central Iberian and Ossa‐Morena zones is a suture of the Variscan belt.

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HP-LT assemblages and minerals are described for the first time in the Alpujarride nappes of the Central and Eastern Betic Cordilleras. These assemblages occur in Permo-Triassic metapelites and include ferro-and magnesio-carpholite, aragonite, kyanite and Mg-rich chloritoid. The estimated P-T conditions range from 4-5 kbar at 280-300 °C to 7-9 kbar at 450-500 °C. Hence, these nappes underwent HP-LT metamorphism (thermal gradient of 12-16 °C/km), just as did the underlying Nevado-Filabride units, prior to their low-to intermediate pressure evolution.

A crustal geotraverse through the Iberian Variscides is presented by integrating the available geological and seismic profiling data. Different modes of orogenic shortening are identified, with varying degrees of coupling between upper and lower crust. In northern and southern regions of the geotraverse, a decoupling in the middle crust permits the lower crust to subduct/underthrust, thus compensating for strong upper crustal shortening. This behavior does not result in great crustal thickening, except in sectors of crustal underthrusting. In southern Central Iberia, moderate upper crustal shortening is due to a mechanically strong lower crust impeded to subduct/underthrust. In this region, shortening is partitioned between upper and lower crust, deformation being distributed in the upper crust while localized at major fault zones in the lower crust. Finally, the central region of the geotraverse (northern Central Iberia) shows a coupled crustal deformation, having given way to the largest orogenic thickening in the Iberian Variscides. The thermal maturity of this much thickened crust originated voluminous crustal melting, and concomitant normal‐fault detachments developed, while shortening dominated in other regions. Theoretical models suggest that compressive stresses may prevail in the lower crust beneath the extending upper crust, thus explaining the efficient syncollisional exhumation in this part of the orogen. A particular feature of the Iberian Variscan geotraverse is the great importance of out‐of‐section mass movements, mainly left‐lateral shear zones concentrated in two suture boundaries, which displaced to the NW (present coordinates) central and northern Iberia with respect to southern Iberia.

ALCUDIA is a 230 km long, vertical incidence deep seismic reflection transect acquired in spring 2007 across the southern Central Iberian Zone (part of the pre‐Mesozoic Gondwana paleocontinent) of the Variscan Orogen of Spain. The carefully designed acquisition parameters resulted in a 20 s TWTT deep, 60–90 fold, high‐resolution seismic reflection transect. The processed image shows a weakly reflective upper crust (the scarce reflectivity matching structures identified at surface), a thick, highly reflective and laminated lower crust, and a flat Moho located at 10 s TWTT (∼30 km depth). The transect can be divided into three segments with different structural styles in the lower crust. In the central segment, the lower crust is imaged by regular, horizontal and parallel reflectors, whereas in the northern and southern segments it displays oblique reflectors interpreted as an important thrust (north) and tectonic wedging involving the mantle (south). The ALCUDIA seismic image shows that in an intracontinental orogenic crust, far from the suture zones, the upper and lower crust may react differently to shortening in different sectors, which is taken as evidence for decoupling. The interpreted structures, as deduced from surface geology and the seismic image, show that deformation was distributed homogeneously in the upper crust, whereas it was concentrated in wedge/thrust structures at specific sectors in the lower crust. The seismic image also shows the location of late Variscan faults in spatial association with the lower crustal thickened areas.