Figure 8 - uploaded by Juan Gómez Barreiro
Content may be subject to copyright.
Idealized reconstruction of the ophiolite that forms part of the Somozas mélange. This ophiolite is currently fragmented and involved in a composite tectonic mélange. 

Idealized reconstruction of the ophiolite that forms part of the Somozas mélange. This ophiolite is currently fragmented and involved in a composite tectonic mélange. 

Source publication
Book
Full-text available
Allochthonous ophiolitic units in the northwestern Iberian Massif are remnants of peri-Gondwanan Paleozoic oceans sandwiched among other exotic terranes of continental and volcanic-arc derivation. All these terranes define an intricate suture zone that marks the convergence and collision between Laurussia and Gondwana. The suture is defined by thre...

Similar publications

Article
Full-text available
The Eastern Pampean Ranges comprise high-grade supracrustal sequences with linear belts of mafic-ultramafic bodies representing ophiolite remnants. New U-Pb and Nd isotopic data suggest that the tectonic evolution of the Pampean Ranges started ca. 640 Ma with the deposition of supracrustal sequences in a backarc basin between a Neoproterozoic magma...
Article
Full-text available
The Kłodzko Metamorphic Complex comprises a number of thrust units, consisting of meth-igneous and metasedimentary rocks of the Variscan basement of the Sudetes, NE Bohemian Massif. The thrust sheet stack rests upon unmetamorphosed Nowa Ruda ophiolite and is unconformably overlain by Frasnian-Fammenian sediments. The studied rocks underwent six def...
Article
Full-text available
Detailed field work conducted in the Dunnage zone of the Quebec Appalachians, is herein combined with 40Ar/39Ar dating on a series of ophiolitic massifs, crosscutting granites, and associated metamorphic rocks occurring along the Baie Verte–Brompton line, the Taconian suture between Laurentia and Lower Paleozoic peri-Laurentian oceanic terranes. St...
Article
Full-text available
A Middle Devonian suprasubduction zone ophiolite, the Careó n Unit (northwest Spain), displays amphibolite-facies ductile deformation fabrics related to the onset of the Rheic Ocean closure. Two different fabrics, an early high-T foliation and a subsequent lower-T foliation, each of which characterized by distinct deformation mechanisms, have been...
Article
Full-text available
Recent models propose that the exhumation of high-pressure rocks occurs by means of return flow inside a low-viscosity channel of serpentinite situated between the plates. To test this hypothesis, we investigated a serpentinite mélange in the Western Alps, which contains exotic mafic and metasedimentary tectonic blocks, recording heterogeneous meta...

Citations

... Important changes in the rheology of the crust have also been reported at those depths (Maggini and Caputo, 2020;Wever, 1989), supporting the idea that a mechanical boundary must exist. Thus, we suggest that, even though it is not observed everywhere (Litak and Brown, 1989), this feature is an orogen-scale, world-class continental crustal discontinuity (Artemieva, 2009), often coinciding with the top of the highly laminated lower crust (when there is one). Its existence might determine the way the crust deforms, easing decoupled deformation. ...
Article
Full-text available
Normal incidence seismic data provide the best images of the crust and lithosphere. When properly designed and continuous, these sections greatly contribute to understanding the geometry of orogens and, along with surface geology, unraveling their evolution. In this paper we present the most complete transect, to date, of the Iberian Massif, the westernmost exposure of the European Variscides. Despite the heterogeneity of the dataset, acquired during the last 30 years, the images resulting from reprocessing the data with a homogeneous workflow allow us to clearly define the crustal thickness and its internal architecture. The Iberian Massif crust, formed by the amalgamation of continental pieces belonging to Gondwana and Laurussia (Avalonian margin), is well structured in the upper and lower crust. A conspicuous mid-crustal discontinuity is clearly defined by the top of the reflective lower crust and by the asymptotic geometry of reflections that merge into it, suggesting that it has often acted as a detachment. The geometry and position of this discontinuity can give us insights into the evolution of the orogen (i.e., of the magnitude of compression and the effects and extent of later-Variscan gravitational collapse). Moreover, the limited thickness of the lower crust below, in central and northwestern Iberia, might have constrained the response of the Iberian microplate to Alpine shortening. Here, this discontinuity, featuring a Vp (P-wave velocity) increase, is observed as an orogen-scale boundary with characteristics compatible with those of the globally debated Conrad discontinuity.
... In contrast, many researchers who focus on the geological evolution of the late Paleozoic Variscan orogen in continental Europe (e.g., Robardet, 2002Robardet, , 2003Linnemann et al., 2004Linnemann et al., , 2008Gutiérrez-Alonso et al., 2008, 2011Kroner and Romer, 2013;Pastor-Galán et al., 2013;Fernández-Suárez et al., 2014) contend that these domains collectively represent a contiguous promontory of Gondwana throughout the Paleozoic (e.g., Quesada, 1991Quesada, , 2006Winchester et al., 2002) that collided with Laurussia (e.g., Matte, 1986;Quesada, 1991Quesada, , 2006 possibly as early as the Early Devonian (ca. 400 Ma; Arenas et al., 2007aArenas et al., , 2007bArenas et al., , 2014Martínez Catalán, 2011;Kroner and Romer, 2013;Arenas and Sánchez Martínez, 2015;Martínez Catalán et al., 2019;Oliveira et al., 2019;Stephan et al., 2019). If correct, the Variscan orogenic belt would be the result of a continent-continent collision between Laurussia and the northern margin of Gondwana. ...
... The most external domain of the Variscan orogenic belt has Laurussian (Avalonian) affinity and includes southern Britain and Ireland, as well as the South Portuguese, Rheno-Hercynian, and Moravo-Silesian zones (Matte, 1986;Quesada, 1991Quesada, , 2006Franke, 2000;Ribeiro et al., 2007). This domain is separated from two roughly concentric domains with Gondwanan affinity by allochthonous complexes that include obducted ophiolites that were subjected to polydeformation and high-pressure (HP) metamorphism and are commonly interpreted to reflect the rootless suture zone of the Rheic Ocean (e.g., Arenas et al., 2007aArenas et al., , 2007bArenas et al., , 2014. In NW Iberia these complexes constitute the upper and middle nappes of the Galicia-Trás-os-Montes Zone (Martínez Catalán et al., 2019). ...
... During this interval, promontory collision continued, as evident from the deformation in southern Britain and Ireland and by the HP metamorphism of the allochthons in NW Iberia, the lowermost of which ("basal units" with the Gondwanan affinity) were exhumed by ca. 370 Ma during the propagation of the collisional deformation toward the Gondwanan foreland (Arenas et al., 2007a(Arenas et al., , 2007b(Arenas et al., , 2014Martínez Catalán et al., 2019). This time interval also saw the initiation of subduction of Paleotethys oceanic lithosphere beneath the eastern margin of the promontory, as suggested by the Devonian bilateral subduction under Bohemia (Franke, 2000) and evidence of HP metamorphism in regions (Alps, Corsica and Sardinia) located close to the southeastern margin of the promontory facing the Paleotethys (Matte, 1986). ...
Article
Full-text available
The supercontinent Pangea formed by the subduction of the Iapetus and Rheic oceans between Gondwana, Laurentia, and Baltica during mid-to-late Paleozoic times. However, there remains much debate regarding how this amalgamation was achieved. Most paleogeographic models based on paleomagnetic data argue that the juxtaposition of Gondwana and Laurussia (Laurentia-Baltica) was achieved via long-lasting highly oblique convergence in the late Paleozoic. In contrast, many geology-based reconstructions suggest that the collision between the two continents was likely initiated via a Gondwanan promontory comprising the Iberian, Armorican, and Bohemian massifs, and parts of the basement units in the Alpine orogen during the Early Devonian. To help resolve this discrepancy, we present an updated compilation of high-quality paleopoles of mid-to-late Paleozoic ages (spanning Middle Ordovician and Carboniferous times) from Gondwana, Laurentia, and Baltica. These paleopoles were evaluated with the Van der Voo selection criteria, corrected for inclination error where necessary, and were used to revise their apparent polar wander (APW) paths. The revised APW paths were constructed using an innovative approach in which age errors, A95 ovals, and Q-factors of individual paleopoles are taken into account. By combining the resulting APW paths with existing geological data and field relationships in the European Variscides, we provide mid-to-late Paleozoic paleogeographic reconstructions which indicate that the formation of Pangea was likely initiated at 400 Ma via the collision between Laurussia and a ribbon-like Gondwanan promontory that was itself formed by a scissor-like opening of the Paleotethys Ocean, and that the amalgamation culminated in the mostly orthogonal convergence between Gondwana and Laurussia.
... Among them, the Cambro-Ordovician ophiolite of Bazar was affected by early low-to medium-P granulites facies metamorphism dated at around 475 ± 2 Ma (Sánchez . The origin and meaning of this metamorphic event are not clear, having been interpreted as related to subduction of a very young oceanic lithosphere, with an eventual consumption of a mid-ocean ridge (Arenas et al. 2007b;Sánchez Martínez et al. 2012). However, the main deformation fabric (amphibolite facies) seems to be kinematically related to the Variscan emplacement (Gómez Barreiro and Martínez Catalán 2012). ...
Chapter
Full-text available
The Variscan deformation in the Iberian Massif is related to the large-scale plate tectonic scenario that drove to the destruction of the Rheic and other intervening oceans, to finally form the Pangea Supercontinent. The Northern Iberian Massif structure consists in an East-vergent orogenic wedge developed at the footwall of a rootless oceanic suture. The collisional architecture of this wedge has been strongly modified by extensional tectonics in the hinterland and orocline formation affecting the whole domain. The Southwestern Iberian Massif transect contains two orogenic sutures cropping out at both boundaries of the OMZ and shows a general transpressive character of the whole collisional evolution, as well as an Early Carboniferous transtensional/extensional stage that gave way to flysch sedimentation, voluminous bimodal magmatism and oblique left-lateral extensional shearing.
... Among them, the Cambro-Ordovician ophiolite of Bazar was affected by early low-to medium-P granulites facies metamorphism dated at around 475 ± 2 Ma (Sánchez . The origin and meaning of this metamorphic event are not clear, having been interpreted as related to subduction of a very young oceanic lithosphere, with an eventual consumption of a mid-ocean ridge (Arenas et al. 2007b;Sánchez Martínez et al. 2012). However, the main deformation fabric (amphibolite facies) seems to be kinematically related to the Variscan emplacement (Gómez Barreiro and Martínez Catalán 2012). ...
Chapter
Full-text available
The Variscan deformation in the Iberian Massif is related to the large-scale plate tectonic scenario that drove to the destruction of the Rheic and other intervening oceans, to finally form the Pangea Supercontinent. The Northern Iberian Massif structure consists in an East-vergent orogenic wedge developed at the footwall of a rootless oceanic suture. The collisional architecture of this wedge has been strongly modified by extensional tectonics in the hinterland and orocline formation affecting the whole domain. The Southwestern Iberian Massif transect contains two orogenic sutures cropping out at both boundaries of the OMZ and shows a general transpressive character of the whole collisional evolution, as well as an Early Carboniferous transtensional/extensional stage that gave way to flysch sedimentation, voluminous bimodal magmatism and oblique left-lateral extensional shearing.
... The study area is located in the NW of Spain and belongs to the Cabo Ortegal Complex, one of the five allochthonous complexes outcropping in the NW of the Iberian Massif and framed within a context of collision between Gondwana and Laurasia [22][23][24][25] (Figure 1). ...
... The different units are fragments of the lithospheric mantle at the base of the ophiolitic complexes and they have undergone several metamorphic events before being piled up and incorporated into the autochthonous terrane [19]. Serpentinization and tectonic structure is well known [23,24,26,27], and three different units can be distinguished at the complex: The Basal Unit, The Ophiolitic Unit, and the Upper Unit. Within the Ophiolitic Unit, the Somozas Mélange has been described, where two sub-units can be differentiated. ...
Article
Full-text available
Serpentinites are characterized by highly variable mineralogical, physical, and mechanical properties. Serpentinites from Moeche (North Western Spain) have been studied to establish their mineralogical, petrographic, and textural characteristics, as well as their physical and mechanical parameters and the factors influencing rock failure, to evaluate the possible use of these rocks either for new construction or for conservation-restoration of the architectonic heritage of the region. In this paper, we highlight the importance of a detailed mineralogical and petrographic characterization in the fracture zones, which will determine the viability of quarrying the stone. A strong correlation between the petrographic features and the uniaxial compression strength values has been observed. The most important aspects were found to be the rock texture, the mineralogical composition of the fracture area and foliation, although mineralogy was also found to be involved (% of carbonates) in the strength of the stone. An important preliminary result of the study was the low asbestos content of these serpentinites, which will help in the potential re-opening of the quarries.
... Presently, there is only one Rb-Sr whole rock isochrone age of 482 ± 20 Ma of an augengneiss from the Liegend-Serie ( Söllner et al., 1981), whereas the nature and age of most ortho-and paragneisses of the Münchberg Massif are completely unknown. Walter, 2003;Arenas et al., 2007;Fuenlabrada et al., 2012) and the location of the study area. Geological map (b) of the Münchberg Massif and the surrounding Palaeozoic rocks (modified after ). ...
... Furthermore, it is reflected by bimodal rock suites consisting of felsic volcanics and mostly MORB-type mafic rocks, in the Vesser Zone north of the Schwarzburg Anticline ( Bankwitz et al., 1994;Kemnitz et al., 2002), from calc-alkaline to alkaline volcanism in the Teplá-Barrandian Unit ( Sláma et al., 2008;Žák et al., 2013), from the "Leptyno-Amphibolitic Complex", forming the base of the Upper Gneiss Unit of the French Massif Central (e.g. Briand et al., 1991;Pin and Lancelot, 1982;Santallier et al., 1988;Chelle-Michou et al., 2017;Lotout et al., 2017), and from the allochthonous nappe complex in NW Spain, in particular from the Lower Ophiolitic Units ( Arenas et al., 2007Arenas et al., , 2016Sánchez Martínez et al., 2012Sánchez Martínez et al., , 2013) and the Upper Units ( Abati et al., 1999;Andonaegui et al., 2012;Arenas et al., 2016). All these rock units are interpreted to result from rift-related magmatism due to separation of the Avalonia microterrane from peri-Gondwana, leading to successive opening of the Rheic ocean ( Linnemann et al., 2010a;Romer et al., 2010 and references therein). ...
Article
The Münchberg Massif in northeastern Bavaria, Germany is an allochthonous metamorphic nappe complex within the Saxothuringian Zone of the Variscan orogen. From top to bottom it consists of four major units: Hangend-Serie, Liegend-Serie, Randamphibolit-Serie and Prasinit-Phyllit-Serie, which show an inverted metamorphic gradient of eclogite- to amphibolite-facies (top) to greenschist-facies (bottom) and are separated from each other by thrust faults. New geochemical and U-Pb zircon data indicate that the four units host metasedimentary and meta-igneous rocks which were formed at different time and in distinct geotectonic settings during the evolution of the Saxothuringian terrane between 550 and 370 Ma. Mafic and felsic protoliths of the Hangend-Serie result from a bimodal magmatism in an evolved oceanic to continental magmatic arc setting at about 550 Ma. These rocks represent relics of the Cadomian magmatic arc, which formed a cordillera at the northern margin of Gondwana during the Neoproterozoic. The Liegend-Serie hosts slivers of granitic orthogneisses, emplaced during magmatic events at c. 505 and 480 Ma, and Early Palaeozoic paragneisses, with our samples deposited at ≤ 483 Ma. Ortho- and paragneisses were affected by an amphibolite-facies metamorphic overprint at c. 380 Ma. Granite emplacement and sediment deposition can be related to the separation of the Avalonia microterrane from the northern Gondwana margin. Amphibolite protoliths of the Randamphibolit-Serie emplaced at c. 400 Ma. They show MORB to E-MORB signatures, pointing to their formation along an oceanic spreading centre within the Rheic ocean. Mafic igneous rocks in the Prasinit-Phyllit-Serie emplaced at nearly the same time (407–401 Ma), but their calc-alkaline to tholeiitic character rather suggests formation in an intra-oceanic island arc/back arc system. This convergent margin lasted for about 30 Ma until the Late Devonian, as is suggested by a maximum deposition age of 371 Ma of associated phyllites, and by metamorphic Ar-Ar ages of 374–368 Ma. The timing of the different magmatic and sedimentary events in the Münchberg Massif and their plate tectonic settings are similar to those estimated for other Variscan nappe complexes throughout Europe, comprising the French Massif Central and NW Spain. This similarity indicates that the Münchberg Massif forms part of a European-wide suture zone, along which rock units of different origin were assembled in a complex way during the Variscan Orogeny.
... The tectonometamorphic evolution of the different units that constitute the allochthonous ensemble is complex (e.g., Arenas et al., 2016). Specific data are available in numerous works about the basal allochthonous units (e.g., Martínez Catalán et al., 1996;Llana-Fúnez and Marcos, 2002;Rodríguez et al., 2003;Gómez Barreiro et al., 2010;Díez Fernández et al., 2011;López-Carmona et al., 2014), the allochthonous ophiolitic units (e.g., Díaz Arenas et al., 2007aArenas et al., , 2007b, and about the upper allochthonous units (e.g., Abati et al., 1999;Ábalos et al., 2003;Gómez Barreiro et al., 2007). The emplacement of the allochthonous units towards the east and onto their relative autochthon, which now crops out in the dome infrastructure, has been dated at~340 Ma (Martínez Catalán et al., 1996;Dallmeyer et al., 1997). ...
... The subsequent separation of Avalonia and opening of the Rheic ocean is documented by the development of a Lower Ordovician passive continental margin Nance et al., 2010). This Cambrian-Ordovician geodynamic evolution is attributed either to ridge-trench collision S anchez-Garc ıa et al., 2008S anchez-Garc ıa et al., , 2010 or back-arc spreading in front of outboard Iapetus/Tornquist ocean subduction driven by either proximal slab roll-back or distal slab pull (Van Staal et al., 1998;Arenas et al., 2007;Catal an et al., 2009). ...
Article
Rift-related regional metamorphism of passive margins is usually difficult to observe on the surface, mainly due to its strong metamorphic overprint during the subsequent orogenic processes that cause its exposure. However, recognition of such a pre-orogenic evolution is achievable by careful characterization of the polyphase tectono-metamorphic record of the orogenic upper plate. A multidisciplinary approach, involving metamorphic petrology, P–T modelling, structural geology and in situ U-Pb monazite geochronology using laser-ablation split-stream inductively coupled plasma mass spectrometry, was applied to unravel the polyphase tectono-metamorphic record of metapelites at the western margin of the Teplá-Barrandian domain in the Bohemian Massif. The study resulted in discovery of three tectono-metamorphic events. The oldest event M1 is LP–HT regional metamorphism with a geothermal gradient between 30 and 50 °C km−1, peak temperatures up to 650 °C and of Cambro-Ordovician age (c. 485 Ma). The M1 event was followed by M2-D2, which is characterized by a Barrovian sequence of minerals from biotite to kyanite and a geothermal gradient of 20–25 °C km−1. D2-M2 is associated with a vertical fabric S2 and was dated as Devonian (c. 375 Ma). Finally, the vertical fabric S2 was overprinted by a D3-M3 event that formed sillimanite to chlorite bearing gently inclined fabric S3 also of Devonian age. The high geothermal gradient of the M1 event can be explained as the result of an extensional, rift-related tectonic setting. In addition, restoration of the deep architecture and polarity of the extended domain before the Devonian history – together with the supracrustal sedimentary and magmatic record – lead us to propose a model for formation of an Ordovician passive continental margin. The subsequent Devonian evolution is interpreted as horizontal shortening of the passive margin at the beginning of Variscan convergence, followed by detachment-accommodated exhumation of lower-crustal rocks. Both Devonian shortening and detachment occurred in the upper plate of a Devonian subduction zone. The tectonic evolution presented in this article modifies previous models of the tectonic history of the western margin of the Teplá-Barrandian domain, and also put constraints on the evolution of the southern margin of the Rheic ocean from the passive margin formation to the early phases of Variscan orogeny.
... The core of the orogenic system, the -Moldanubian zone‖ (Ballèvre et al., 2014), extends from the Bohemian Massif in the East, to the Black Forest and Vosges, to fragments in the Alpine belt, the French Massif Central, southern Armorica and North-Western Spain (the Galicia-Tres Montes Zone). In France and Spain, this zone corresponds to a complex of mostly south-verging allochtonous nappes that include ophiolitic remains (Lasnier, 1971;Burg et al., 1984;Arenas et al., 2007;Schulmann et al., 2014), high-pressure to ultra-high pressure relicts Lardeaux et al., 2001;Berger et al., 2010;Kotková et al., 2011), and overall high grade (upper amphibolite to granulite facies) rocks . To the south, metamorphic nappes of the Moldanubian zone are thrusted over the para-autochtonous to autochtonous terranes representing the northern passive margin of Gondwana. ...
Article
Earth's continental crust is dominantly made of buoyant, felsic igneous material (granitoids), that were ultimately extracted from the mantle as a result of Earth's differentiation. Since felsic melts are not in chemical equilibrium with the mantle, they can originate either from melting of older crustal lithologies, or from differentiation of a primitive mantle melt; only the latter case will contribute to crustal growth. To understand the mechanisms of continental crust growth and differentiation through time, it is therefore necessary to unravel the respective contribution of these two different mechanisms in the genesis of granitoid suites. In modern Earth, granitoids are chiefly generated in convergent plate boundaries (subduction and collision). This paper examines the granitic suites in a late-collision environment, the Variscan French Massif Central (FMC), and compares them with the suites found in an oceanic arc. We therefore describe, and compare, two end-members sites of granite generation. In the FMC, several main types of granites are described. Muscovite and Cordierite bearing Peraluminous Granites (resp. MPG and CPG) contain large amounts of inherited zircons, and their chemistry demonstrates that their sources were older crustal material (resp. Metasediments and metaigneous). On the other hand, Potassic Calc-alkaline Granites (KCG), associated to potassic diorites (vaugnerites) do not contain inherited zircons, and ultimately derive from the vaugnerites. The vaugnerites in turns form by partial melting of a mantle contaminated by the regional crust. Therefore, although they are isotopically similar to the crust, the KCG are net contributors to crustal growth. Thus we conclude that although late-orogenic settings are dominated by crustal melting and recycling, they may be sites of net crustal growth, even though this is not visible from isotopes only. In contrast, arc granitoids are purely or almost purely mantle derived. However, the preservation potential of arcs is much smaller than the preservation of late-orogenic domains, such that at the scale of a whole orogenic belt, late-orogenic magmatism is probably as important as arc magmatism. Finally, we speculate that the situation may have been similar in the Archaean, or even more skewed towards late-orogenic sites (or similar environments, dominated by melting of a altered mafic protocrust), owing to the hotter mantle and less stable subductions during that period.
... The Allochthonous Ophiolitic Units are made of mafic and ultramafic rocks and scarce metasedimentary rocks (see compilation by Arenas and Sánchez Martínez, 2015). These units can be divided in two groups according to protolith ages and chemical signature (Arenas et al., 2007a;Sánchez Martínez et al., 2009): a Cambrian-Ordovician group related to the closure of the Iapetus/Tornquist Ocean (Bazar ophiolite; Sánchez and opening of the Rheic Ocean s.l. (Vila de Cruces, Izeda-Remondes, and Internal Ossa-Morena Zone Ophiolites; Pin et al., 2006;Arenas et al., 2007b;Pedro et al., 2010), and an Lower-Middle Devonian group (Careón, Purrido, Moeche, and Morais-Talhinhas ophiolites; Díaz García et al., 1999;Pin et al., 2006;Sánchez Martínez et al., 2011) representing an ephemeral oceanic basin formed in early stages of the Variscan orogenesis (Arenas et al., 2014b). ...
... The age of imbrication of the Cambrian-Ordovician and Devonian ophiolitic ensemble exposed in NW Iberia has been constrained, by means of 40 Ar/ 39 Ar dating of their low-to medium-T metamorphic fabrics (greenschist and amphibolite facies), to a range that extends from ca. 391 Ma to ca. 364 Ma Dallmeyer et al., 1997). The metamorphic grade decreases progressively down structure, as the ages of metamorphism become younger (Arenas et al., 2007a). Kinematic indicators for accretion consistently indicate top-to-the-Cantabrian foreland, i.e. subduction under the Upper Allochthonous Units (Arenas et al., 2007b;Gómez Barreiro et al., 2010b). ...
... The tectonic polarity for this event was ruled again by thicker Variscan crust located outboard mainland Gondwana, i.e. subduction to the W and SW in present-day coordinates. Understacking of young (Devonian) oceanic crust under the Upper Allochthonous Units was followed by accretion of older (Cambrian-Ordovician) tracts of transitional crust (Arenas et al., 2007a), and then by subduction of continental crust at ca. 380-370 Ma (Basal Allochthonous Units;Martínez Catalán et al., 1996). Regarding the latter process, insertion of more buoyant lithosphere under the (previous) Lower Devonian high-P metamorphic belt caused further exhumation of the bottom members of the Upper Allochthonous Units via tectonic denudation, which coupled to east-verging folding in response to simple shearing at the base of the upper plate (Gómez . ...
Article
An integrated interpretation of the late Paleozoic structural and geochronological record of the Iberian Massif is presented and discussed under the perspective of a Gondwana-Laurussia collision giving way to the Variscan orogen. Compressional and extensional structures developed during the building of the Variscan orogenic crust of Iberia are linked together into major tectonic events operating at lithosphere scale. A review of the tectonometamorphic and magmatic evolution of the IberianMassif reveals backs and forths in the overall convergence between Gondwana and Laurussia during theamalgamation of Pangea in late Paleozoic times. Stages dominated by lithosphere compression are characterized by subduction, both oceanic and continental, development of magmatic arcs, (over- and under-) thrusting of continental lithosphere, and folding. Variscan convergence resulted in the eventual transference of a large allochthonous set of peri-Gondwanan terranes, the Iberian Allochthon, onto the Gondwana mainland. The Iberian Allochthon bears the imprint of previous interaction between Gondwana and Laurussia, including their juxtaposition after the closure of the Rheic Ocean in Lower Devonian times. Stages governed by lithosphere extension are featured by the opening of two short-lived oceanic basins that dissected previous Variscan orogenic crust, first in the Lower-Middle Devonian, following the closure of the Rheic Ocean, and then in the early Carboniferous, following the emplacement of the peri-Gondwanan allochthon. An additional, major intra-orogenic extensional event in the early-middle Carboniferous dismembered the Iberian Allochthon into individual thrust stacks separated by extensional faults and domes. Lateral tectonics played an important role through the Variscan orogenesis, especially during the creation of new tectonic blocks separated by intracontinental strike-slip shear zones in the late stages of continental convergence.