Tectonic evolution of the boundary between the Central Iberian and Ossa‐Morena zones (Variscan belt, southwest Spain)

Abstract

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.

U–Pb zircon geochronology and petrology of granitoids from Mitwaba (Katanga, Congo): implications for the evolution of the Mesoproterozoic Kibaran belt

“…Bea et al, 1999). The Variscan peraluminous granitoids were produced in a belt thickened by underthrusting of the lower crust (Azor et al, 1994), i.e. a crust thickened by subduction rather than by continental collision.…”

Gravity modeling of the lithosphere in the Calatrava Volcanic Province (Spain): geodynamic implications.

“…The southern termination of this model reaches the boundary between the CIZ and the Ossa Morena Zone(OMZ) located along the NW−SE-trending Badajoz-Cordoba Shear Zone (Burg et al, 1981), later redefined as the Central Unit (CU in Fig. 2; Azor et al, 1994). The filtered observed Bouguer anomaly profile shows a regional gradient with an absolute maximum of -16 mGal at the southwestern end in the CU and an absolute min-2014; Ehsan et al, 2015).…”

“…OMZ= Ossa-Morena Zone. The dashed white line shows the approximate location of boundary between the CIZ and the OMZ, known as the Central Unit (CU; Azor et al, 1994). The rectangle shows the location of figure 3.…”

“…The CIZ is bounded to the south by the Badajoz-Cordoba Shear Zone (Burg et al, 1981), latter redefined as the Central Unit (CU in Fig. 2; Azor et al, 1994), which is a NW−SE-trending 5 km-wide band of high-grade metamorphics with slices of mafic rocks. The Alpine intraplate deformation of the Iberian Massif has been ascribed to crustal-scale buckling processes on the basis of numerical and analogue modeling (Cloetingh et al, 2002;Muñoz-Martín et al, 2010;Fernández-Lozano et al, 2012).…”

Geology and mineralogy of Li mineralization in the Central Iberian Zone (Spain and Portugal)

“…It is limited by the Viveiro Fault and its continuation along the Courel and Peñalba Synclinoriums to the north (Martínez Catalán, 1985), in contact with the West Asturian-Leonese Zone. The Ossa Morena Zone occurs to the south west of the Central Iberian Zone, with the Central Unit of the Badajoz-Córdoba Shear Zone separating both zones (Díez Balda et al, 1990;Azor et al, 1994). The Central Iberian Zone is divided into two subdomains (Pérez-Estaún et al, 2004): (1) the Ollo de Sapo Domain to the north, characterized by broad outcrops of gneisses with coarse ovoid megacrystals of feldspar (augen gneisses), syntectonic granites and high-degree regional metamorphism in some areas; and, (2) the Schist-Metagreywacke Complex Domain to the south, where Neoproterozoic to Lower Palaeozoic metasedimentary rocks including metamorphosed shales, sandstones, and minor conglomerates and limestones, are intruded by abundant granitoids (Fig.…”