serie NOVA TERRA nº 49

37 The Galicia – Ossa-Morena Zone: Proposal for a new zone of the Iberian Massif. Variscan implications Ricardo Arenas a , ⁎ , Rubén Díez Fernández a , Francisco J. Rubio Pascual b , Sonia Sánchez Martínez a , Luis Miguel Martín Parra b , Jerónimo Matas b , José González del Tánago a , Alberto Jiménez-Díaz c , Jose M. Fuenlabrada d , Pilar Andonaegui a , Antonio Garcia-Casco e , f a Departamento de Petrología y Geoquímica e Instituto de Geociencias (UCM, CSIC), Universidad Complutense, 28040 Madrid, Spain b Instituto Geológico y Minero de España, 28760, Tres Cantos, Madrid, Spain c Departamento de Geodinámica, Universidad Complutense, 28040 Madrid, Spain d CAI de Geocronología y Geoquímica Isotópica, Universidad Complutense, 28040 Madrid, Spain e Departamento de Mineralogía y Petrología, Universidad de Granada, 18071 Granada, Spain f Instituo Andaluz de Ciencias de la Tierra (CSIC, UGR), E-18100, Armilla, Granada, Spain a b s t r a c t a r t i c l e i n f o Article history: Received 25 August 2015 Received in revised form 2 February 2016 Accepted 24 February 2016 Available online 2 March 2016 Correlation of a group of allochthonous terranes (referred to as basal, ophiolitic and upper units) exposed in the NW and SW of the Iberian Massif, is used to propose a new geotectonic zone in the southern branch of the Variscan Orogen: the Galicia – Ossa-Morena Zone. Recent advances in SW Iberia identify most of the former Ossa-Morena Zone as another allochthonous complex of the Iberian Massif, the Ossa-Morena Complex, equiva- lent to the Cabo Ortegal, Órdenes, Malpica-Tui, Bragança and Morais complexes described in NW Iberia. The new geotectonic zone and its counterparts along the rest of the Variscan Orogen constitute an Internal Variscan Zone with ophiolites and units affected by high-P metamorphism. The Galicia – Ossa-Morena Zone includes a Variscan suture and pieces of continental crust bearing the imprint of Ediacaran – Cambrian events related to the activity of peri-Gondwanan magmatic arcs (Cadomian orogenesis). In the Iberian Massif, the general struc- ture of this geotectonic zone represents a duplication of the Gondwanan platform, the outboard sections being juxtaposed on top of domains located closer to the mainland before amalgamation. This interpretation offers anexplanation thatovercomes someissues regarding the differences between the stratigraphicand paleontolog- ical record of the central and southern sections of the Iberian Massif. Also, equivalent structural relationships be- tween other major geotectonic domains of the rest of the Variscan Orogen are consistent with our interpretation and allow suspecting similar con fi gurations along strike of the orogen. A number of issues may be put forward in this respect that potentially open new lines of thinking about the architecture of the Variscan Orogen. © 2016 Elsevier B.V. All rights reserved. Keywords: Galicia – Ossa-Morena Zone New geotectonic zone Iberian Massif Variscan Orogen 1. Introduction The IberianMassif, like other sectors of the Variscan Orogen, has been classically divided in geotectonic/paleogeographic zones. Although there is no formal de fi nition for a “ geotectonic zone ” of an orogen, its use is widely accepted to distinguish among orogenic domains with contrasted characteristics regarding their stratigraphy, structure, metamorphism and magmatism (e.g. Hatcher, 1989; Hodges, 2000; Schmid et al., 2004 ). It is also somewhat diffuse the concept of external and internal zones of orogens, although external domains are generally characterized by thin-skinned tectonics, low-grade regional metamorphism and scarce magmatism, while internal domains are characterized by pervasive duc- tile deformation, regional foliations and intense metamorphism and magmatism. In addition, internal zones typically contain the suture or sutures of the orogen, whicharemanifested by the presence of ophiolites and terranes affected by subduction-related high-P metamorphism. In collisional orogens, geotectonic zones can be used to separate different sectors of the colliding continental platforms and tectonic blocks affected by variable intensity of deformation. If well-preserved ophiolites are present, geotectonic zones can also provide information on the oceanic domains closed before collision. Lotze (1945) and Julivert et al. (1972) made the fi rst geotectonic division of the Iberian Massif, which prevailed for a long time. From northeast to southwest, the Cantabrian, West Asturian-Leonese, Central Iberian, Ossa-Morena and South-Portuguese zones were distinguished. Tectonophysics 681 (2016) 135 – 143 ⁎ Corresponding author at: Departamento de Petrología y Geoquímica e Instituto de Geociencias (UCM, CSIC), Facultad de Geología, Universidad Complutense de Madrid, C/ José Antonio Novais, no. 2, 28040 Madrid, Spain. Tel.: +34 913944904. E-mail addresses: arenas@geo.ucm.es (R. Arenas), georuben@usal.es (R. Díez Fernández), f.rubio@igme.es (F.J. Rubio Pascual), s.sanchez@geo.ucm.es (S. Sánchez Martínez), lm.martin@igme.es (L.M. Martín Parra), j.matas@telefonica.net (J. Matas), tanago@ucm.es (J. González del Tánago), ajimenezdiaz@geo.ucm.es (A. Jiménez-Díaz), jmfuenla@pdi.ucm.es (J.M. Fuenlabrada), andonaeg@geo.ucm.es (P. Andonaegui), agcasco@ugr.es (A. Garcia-Casco). http://dx.doi.org/10.1016/j.tecto.2016.02.030 0040-1951/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto