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Moreira N.,Laboratorio Of Investigacao Of Rochas Industriais E Ornamentais Da Ectue | Dias R.,Laboratorio Of Investigacao Of Rochas Industriais E Ornamentais Da Ectue | Dias R.,University of Evora | Araujo A.,University of Evora | Pedro J.,University of Evora
Comunicacoes Geologicas | Year: 2014

The Alter-do-Chão - Elvas Sector is characterized by a thick meta-sedimentary sequence from Neoproterozoic (Ediacarian) and upper Cambrian. In Vila Boim region, outcrops a stratigraphic window where all stratigraphic sequence is exposed (Torre de Cabedal structure). Here is possible to emphasize two main Variscan deformation phases. The first one was developed in an upper structural level and is characterized by recumbent folds with SW vergence, locally reversing the regional stratigraphy. The second deformation event is responsible for refolding previous structures, giving rise to an interference pattern which exposes the Ossa-Morena zone neoproterozoic basement. The second event, which controls the main regional structure, is characterized by NNW-SSE folds, with upright axial planes, sometimes slightly facing to WSW; subparallel to these folds a regional sinistral shear component is found. © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP. Source


Moreira N.,Laboratorio Of Investigacao Of Rochas Industriais E Ornamentais Da Ectue | Araujo A.,University of Evora | Pedro J.,University of Evora | Dias R.,Laboratorio Of Investigacao Of Rochas Industriais E Ornamentais Da Ectue | Dias R.,University of Evora
Comunicacoes Geologicas | Year: 2014

The geodynamic evolution of Ossa-Morena Zone is essential to understand the Variscan Cycle on the Iberian Autochthon Terrain. Several stratigraphic, structural, magmatic and metamorphic studies have been done in this tectonostratigraphic zone. However, these studies must be integrated like an evolutionary sketch of this zone in space and time. This paper is a critical multidisciplinary geodynamical overview of this zone, integrating the previous data, from the initial stages (lower Paleozoic) until the later ones (upper Paleozoic). The (re) interpretation of previous data for this zone has highlighted the presence of several pulses of crustal extension during the early stages of the Variscan cycle (Cambrian-Ordovician), which culminate with Rheic Ocean opening, as well as four tecnonometamorphic and magmatic episodes, related with subduction and continental collision processes (Devonian to Permian), which are responsible for the genesis of the Variscan Iberian Belt. © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP. Source


Dias R.,University of Evora | Dias R.,Laboratorio Of Investigacao Of Rochas Industriais E Ornamentais Da Ectue | Ribeiro A.,University of Lisbon | Coke C.,University of Evora | And 3 more authors.
Comunicacoes Geologicas | Year: 2014

In the Iberian Variscides it is possible to emphasize several curved macrostructures; their characterization and genesis is a matter of controversy. In this work the facts concerning these structures are discussed, as well as the processes related with the formation of the Ibero-Armorican and Cantabrian arcs. The data suggest a poly-phase genesis, where the indentation of a major promontory of Gondwana was a crucial element. © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP. Source


Dias R.,University of Evora | Dias R.,Laboratorio Of Investigacao Of Rochas Industriais E Ornamentais Da Ectue | Ribeiro A.,University of Lisbon | Romao J.,European University of Portugal | And 3 more authors.
Tectonophysics | Year: 2016

In the Iberian Variscides several first order arcuate structures have been considered. In spite of being highly studied their characterization, formation mechanisms and even existence is still debatable.The main Ibero-Armorican Arc (IAA) is essentially defined by a predominant NW-SE trend in the Iberian branch and an E-W trend in the Brittany one. However, in northern Spain it presents a 180° rotation, sometimes known as the Cantabrian Arc (CA). The relation between both arcs is controversial, being considered either as a single arc due to one tectonic event, or as the result of a polyphasic process. According to the last assumption, there is a later arcuate structure (CA), overlapping a previous major one (IAA). Whatever the models, they must be able to explain the presence of a Variscan sinistral transpression in Iberia and a dextral one in Armorica, and a deformation spanning from the Devonian to the Upper Carboniferous. Another arcuate structure, in continuity with the CA, the Central-Iberian Arc (CIA) was recently proposed mainly based upon on magnetic anomalies, geometry of major folds and Ordovician paleocurrents.The critical review of the structural, stratigraphic and geophysical data supports both the IAA and the CA, but as independent structures. However, the presence of a CIA is highly questionable and could not be supported.The complex strain pattern of the IAA and the CA could be explained by a Devonian - Carboniferous polyphasic indentation of a Gondwana promontory. In this model the CA is essentially a thin-skinned arc, while the IAA has a more complex and longer evolution that has led to a thick-skinned first order structure. Nevertheless, both arcs are essentially the result of a lithospheric bending process during the Iberian Variscides. © 2016 Elsevier B.V. Source

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