Person:
Gómez Barreiro, Juan

First Name

Juan

Last Name

Gómez Barreiro

URI

https://hdl.handle.net/20.500.14352/86767

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Mineralogía y Petrología

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Now showing 1 - 10 of 10

Fabric Development in a Middle Devonian Intraoceanic Subduction Regime: The Careón Ophiolite (Northwest Spain)
(The Journal of geology, 2010) Gómez Barreiro, Juan; Martínez Catalán, José Ramón; Prior, D.; Wenk, H.-R.; Vogel, S.; Díaz García, Florentino; Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Lonardelli, I.
A Middle Devonian suprasubduction zone ophiolite, the Careo´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 identified in two distinct crustal-scale shear zones of the same ophiolitic thrust sheet. Combined quantitative texture analysis by electron backscattered diffraction and time-of-flight neutron diffraction, were carried out on the shear zones and correlated with micro- and macrostructural data. The results indicate that the regional lineation and shear zone kinematics (east-west, top-to-the-east) represent fabrics developed essentially during the intraoceanic subduction of the Rheic Ocean, and their orientation may be considered a reference vector for convergence models in this part of the Variscan belt.
Thrust and detachment systems in the Ordenes Complex (northwestern Spain): Implications for the Variscan-Appalachian geodynamics.
(Special paper - Geological Society of America, Variscan-Appalachian dynamics: The building of the late Paleozoic basement, 2002) Martínez Catalán, José Ramón; Díaz García, Florentino; Arenas Martín, Ricardo; Abati Gómez, Jacobo; Castiñeiras García, Pedro; González Cuadra, Pablo; Gómez Barreiro, Juan; Rubio Pascual, Francisco J.; Martínez Catalán, José Ramón; Hatcher, Robert D.; Arenas Martín, Ricardo; Díaz García, Florentino
The allochthonous complexes of northwestern Iberia consist of a pile of units of Gondwanan and peri-Gondwanan provenance, and include oceanic lithosphere. The units are classiµed into upper, intermediate (ophiolitic), and basal. We present a dettailed geological map and sections across the Ordenes Complex, together with a brief description of its units and a discussion of its structures. In the upper units, two complete cycles of burial and exhumation have been identiµed. The first cycle, of Early Ordovician age, records a convergent plate margin, possibly in a peri-Gondwanan domain. The second is Variscan, and the structural evollution of the three groups of allochthonous units re×ects progressive accretion to an acctive orogenic wedge. Continuous understacking of continental and oceanic fragments toward the west began with the upper units and ended with the basal units. The latter represent the outermost margin of Gondwana, and their subduction marked the closure of the intervening ocean, and the change from subduction to a collisional regime. Terrane accretion took place in the Devonian and, during the Late Devonian and the Carboniferous, the deformation progressed inboard of the Gondwana margin. Variscan emplacement of the allochthonous units occurred in two successive thrusting episodes. The µrst placed the basal units over the sedimentary cover of the Gondwana margin in what seems to follow a normal sequence of thrusting. The second carried the upper and ophiolitic units on top of the previous nappe pile and has an out-of-sequence character. A possible correlation of the Early Ordovician convergence, early Variscan accretion, subsequent oceanic closure, continent-continent collision, and renewed thrust activity during the late Carboniferous in northwestern Iberia is established with the Taconian, Acadian, and Alleghanian orogenies in the Appalachians.
Upper crust reworking during gravitational collapse: the Bembibre–Pico Sacro detachment system (NW Iberia)
(Journal of the Geological Society, 2010) Gómez Barreiro, Juan; Martínez Catalán, José Ramón; Díez Fernández, Rubén; Arenas Martín, Ricardo; Díaz García, Florentino
The kinematics of the basal allochthon in the SW of the O´ rdenes Complex is analysed to constraint its evolution during collisional and postcollisional stages of the Variscan orogeny. Two distinct sequences have been identified in the basal allochthon of this sector: the upper and lower sequences, in close correlation with the subdivision of the basal allochthon in the Malpica–Tui Complex. Three main tectonic episodes have been established in the basal allochthon: a high-pressure event related to continental subduction, a mesozonal event of regional exhumation by thrusting and recumbent folding, and a regional-scale extensional episode that resulted in the development of the Bembibre–Pico Sacro detachment system. The Bembibre–Pico Sacro system rejuvenated pre-existing shear zones, whose weakness favoured the nucleation of the detachments. Shear zones associated with the detachments overprinted the previous tectonic fabrics under conditions ranging from lower amphibolite to greenschist facies, and with heterogeneously distributed ductile to brittle deformation. The detachment system is coeval with late orogenic collapse and widespread magmatism, and represents its upper crustal expression. It correlates with mid- and lower crustal flow and the development of gneiss domes at depth in such a way that the basal allochthon can be considered a rheological boundary between the more rigid allochthonous sequences above and the more viscous Schistose Domain and autochthon below.
Tectonic evolution of the upper allochthon of the Órdenes complex (northwestern Iberian Massif): Structural constraints to a polyorogenic peri-Gondwanan terrane
(The Evolution of the Rheic Ocean: From Avalonian-Cadomian Active Margin to Alleghenian-Variscan Collision, 2007) Gómez Barreiro, Juan; Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Castiñeiras García, Pedro; Abati Gómez, Jacobo; Díaz García, Florentino; Wijbrans, Jan R.; Linnemann, Ulf; Nance, R. Damian; Kraft, Petr; Zulaud, Gernold
The upper allochthon of northwest Iberia represents the most exotic terrane of this part of the European Variscan belt. Recent advances in the metamorphic petrology, structural geology, and geochronology of the upper allochthon in the Órdenes complex are integrated into a synthesis of its tectonic evolution, constraining the main tectonothermal events. Important aspects of this synthesis are (1) the interpretation of Cambro-Ordovician magmatism and earliest metamorphic event, as the result of drifting of a peri-Gondwanan terrane; (2) the subsequent shortening and crustal thickening of the terrane related to its subduction and accretion to Laurussia; (3) a younger cycle of shortening and extension resulting from convergence between Laurussia and Gondwana; and (4) the emplacement of this exotic terrane as the upper allochthon, together with underlying ophiolitic and basal allochthons, during the Laurussia-Gondwana collision. Implications derived from the well-established tectonothermal sequence are discussed in the context of Paleozoic paleogeography and geodynamics. The evolution of this part of the belt is related first to the closure of the Tornquist Ocean, and later to that of the eastern branch of the Rheic Ocean. Furthermore, the relative paleopositions of the upper allochthon and the Iberian autochthon in northern Gondwana are discussed.
40Ar/39Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia
(Journal of the Geological Society, 2006) Gómez Barreiro, Juan; Wijbrans, Jan R.; Castiñeiras García, Pedro; Martínez Catalán, José R.; Arenas Martín, Ricardo; Díaz García, Florentino; Abati Gómez, Jacobo
The tectonothermal evolution of a polyorogenic terrane in the Variscan belt of NW Spain has been constrained by 40Ar/39Ar laserprobe incremental heating experiments on mylonitic fabrics developed in major structures. Transitional levels between HP–HT and IP upper units in the O´ rdenes Complex where metamorphic and structural records demonstrate two cycles of burial and exhumation were selected for dating. Two groups of ages have been defined: (1) Silurian–Early Devonian, obtained from mylonites of the Forna´s extensional detachment, here considered as the minimum age for the start of tectonic exhumation of the HP– HT units and an upper age-limit for the HP–HT event itself; (2) Early to Mid-Devonian, from structures related to the Variscan convergence in the area, which include top-to-the-east thrusts and extensional detachments. A single, younger Carboniferous age obtained from the uppermost allochthonous sequences possibly reflects the final stages of emplacement of the allochthonous complexes. Our data indicate a polyorogenic character for a part of the Iberian allochthonous complexes, including Variscan (sensu stricto) and Early Variscan convergence, as well as an older, Early Palaeozoic cycle.
Careón ophiolite, NW Spain: Suprasubduction zone setting for the youngest Rheic Ocean fl oor
(Geology (Boulder Colo.), 2007) Sánchez Martínez, Sonia; Arenas Martín, Ricardo; Díaz García, Florentino; Martínez Catalán, José Ramón; Gómez Barreiro, Juan; Pearce, Julian A.
The Careón ophiolite (Galicia, NW Iberian Massif) shows lithological and geochemical features suggestive of an origin in a suprasubduction zone setting. As with other Devonian ophiolites in the European Variscan belt, it was generated within a contracting Rheic Ocean. This setting and the general absence of large Silurian-Devonian volcanic arcs on both of the Rheic Ocean margins strongly suggest that this ocean was closed by intraoceanic subduction directed to the north. This subduction removed the older normal (N) mid-oceanic-ridge basalt (MORB) oceanic lithosphere and gave rise to a limited volume of new suprasubduction zone oceanic lithosphere. The Careón ophiolite is a key element in understanding the evolution of the Rheic Ocean, which was the main oceanic domain that closed during the Paleozoic convergence of Gondwana and Laurussia, preceding the assembly of Pangea
REE-assisted U–Pb zircon age (SHRIMP) of an anatectic granodiorite: Constraints on the evolution of the A Silva granodiorite, Iberian allochthonous complexes
(Lithos, 2010) Castiñeiras García, Pedro; Díaz García, Florentino; Gómez Barreiro, Juan
The A Silva granodiorite is a plutonic body intruded into the metasediments of the upper unit of the Órdenes Complex (Variscan belt, NW Spain). These metasediments represent the middle section of a magmatic arc located in northern Gondwana. The A Silva granodiorite has been classically considered a late Variscan granite. In this work, new field mapping, structural analysis, and SHRIMP U–Pb zircon dating indicate the granodiorite is significantly older. However, the data indicate a concordant age range between 540 and 460 Ma, and therefore CL images are not useful toward the interpretation of the geochronological results. This issue can be unravelled by using the hafnium and rare earth element composition of zircon in the assessment of the age. In this way, we determined that the age distribution was the result of lead loss, rather than a real age scatter or inheritance, and we could obtain a 206Pb/238U crystallization age of 510.28 (+1.57, −1.44)Ma using the TuffZirc algorithm. This age together with the well-preserved field relationships of the host rock permit us to interpret the A Silva granodiorite as multiple sheets intruded into a sequence of metatexitic host rocks after crustal thickening and subsequent decompression that developed coeval with partial melting during the latest stages of a regional extensional event. Taken together with the underlying Monte Castelo gabbro (499± 2 Ma), the whole plutonic complex reaches 8 km in thickness and forms an antiformal stack structure in a shear parallel (N–S) cross-section. This structure could be responsible for previously described, localized granulite facies metamorphism. The presence of a late Cambrian magmatic event has been widely reported in other areas of northern Gondwana and it is related to the opening of the Rheic Ocean.
Paleozoic ophiolites in the Variscan suture of Galicia (northwest Spain): Distribution, characteristics, and meaning
(4-D Framework of Continental Crust, 2007) Arenas Martín, Ricardo; Martínez Catalán, José Ramón; Sánchez Martínez, Sonia; Díaz García, Florentino; Abati Gómez, Jacobo; Fernández Suárez, Javier; Andonaegui Moreno, María Del Pilar; Gómez Barreiro, Juan; Hatcher, Robert D.; Carlson, Marvin P.; McBride, John H.; Martínez Catalán, José Ramón
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 defi ne an intricate suture zone that marks the convergence and collision between Laurussia and Gondwana. The suture is defi ned by three different ophiolitic ensembles: upper ophiolitic units, lower ophiolitic units, and the Somozas mélange. The lower ophiolitic units were derived from an alternation of basalts and sediments intruded by gabbros and scarce granitoids, and they formed during the opening of a marginal basin, the Galician ocean, during Late Cambrian to Early Ordovician time. This ocean was created as a back arc by the severance of a volcanic arc that had developed at the northern margin of Gondwana and formed part of the Rheic oceanic realm. The upper ophiolitic units formed during the Early Devonian from intraoceanic subduction in the early Paleozoic lithosphere of the Rheic Ocean. These suprasubduction ophiolites were formed just before the ocean closed, preceding the collision between Gondwana and Laurussia. The Somozas mélange appears in an anomalous position at the base of the Cabo Ortegal Complex. The ophiolites involved in this tectonic mélange represent an imbricate of highly dismembered oceanic lithosphere, slivers of subducted outer edge of the Gondwanan continental margin, and Paleozoic metasediments of the northern Gondwanan platform. The ophiolites might either record the development of a different peri-Gondwanan oceanic domain, or they might be equivalent to any of the other ophiolitic ensembles, and their anomalous structural position is simply a consequence of complex thrusting.
Space and time in the tectonic evolution of the northwestern Iberian Massif: Implications for the Variscan belt.
(4-D Framework of Continental Crust, 2007) Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Díaz García, Florentino; González Cuadra, Pablo; Gómez Barreiro, Juan; Abati Gómez, Jacobo; Castiñeiras García, Pedro; Fernández Suárez, Javier; Sánchez Martínez, Sonia; Andonaegui Moreno, María Del Pilar; González Clavijo, Emilio; Díez Montes, Alejandro; Rubio Pascual, Francisco J.; Valle Aguado, Beatriz; Hatcher, Robert D.; Carlson, Marvin P.; McBride, John H.; Martínez Catalán, José Ramón
Recent advances in geochemical studies of igneous rocks, isotopic age data for magmatism and metamorphism, quantitative pressure-temperature (P-T) estimates of metamorphic evolution, and structural geology in the northwestern Iberian Massif are integrated into a synthesis of the tectonic evolution that places the autochthonous and allochthonous terranes in the framework of Paleozoic plate tectonics. Because northwestern Iberia is free from strike-slip faults of continental scale, it is retrodeformable and preserves valuable information about the orthogonal component of convergence of Gondwana with Laurentia and/or Baltica, and the opening and closure of the Rheic Ocean. The evolution deduced for northwest Iberia is extended to the rest of the Variscan belt in an attempt to develop a three-dimensional interpretation that assigns great importance to the transcurrent components of convergence. Dominant Carboniferous dextral transpression following large Devonian and Early Carboniferous thrusting and recumbent folding is invoked to explain the complexity of the belt without requiring a large number of peri-Gondwanan terranes, and its ophiolites and highpressure allochthonous units are related to a single oceanic closure. Palinspastic reconstruction of the Variscan massifs and zones cannot be achieved without restoration of terrane transport along the colliding plate margins. A schematic reconstruction is proposed that involves postcollisional strike-slip displacement of ~3000 km between Laurussia and Gondwana during the Carboniferous.
A rootless suture and the loss of the roots of a mountain chain: The Variscan belt of NW Iberia
(Comptes rendus. Géoscience, 2009) Martínez Catalán, José R.; Arenas Martín, Ricardo; Abati Gómez, Jacobo; Sánchez Martínez, Sonia; Díaz García, Florentino; Fernández Suárez, Javier; González Cuadra, Pablo; Castiñeiras García, Pedro; Gómez Barreiro, Juan; Díez Montes, Alejandro; González Clavijo, Emilio; Rubio Pascual, Francisco J.; Andonaegui Moreno, María Del Pilar; Jeffries, Teresa E.; Alcock, James E.; Díez Fernández, Rubén; López Carmona, Alicia
Ophiolites of different Paleozoic ages occur in North-West (NW) Iberia in a rootless suture representing the remnants of the Rheic Ocean. Associated allochthonous terranes in the hanging- and foot-walls of the suture derive from the former margins, whereas the relative autochthon corresponds to the Paleozoic passive margin of northern Gondwana. The Paleozoic tectonic evolution of this part of the circum-Atlantic region is deduced from the stratigraphical, petrological, structural and metamorphic evolution of the different units and their ages. The tectonic reconstruction covers from Cambro-Ordovician continental rifting and the opening of the Rheic Ocean to its Middle to Upper Devonian closure. Then, the Variscan Laurussia–Gondwana convergence and collision is briefly described, from its onset to the late stages of collapse associated with the demise of the orogenic roots. [RÉSUMÉ] Une suture sans racines et la perte des racines d’une chaîne montagneuse : la chaîne varisque du Nord-Ouest de l’Ibérie. Des ophiolites d’âges différents affleurent dans le Nord-Ouest de l’Ibérie dans une suture sans racines, témoin de l’océan Rhéïque. Les terrains allochtones sur et sous la suture dérivent de ses deux marges, tandis que l’autochtone relatif appartient à la marge passive du Nord de Gondwana. On peut déduire l’évolution des plaques dans cette partie de la région circum-Atlantique à partir des données stratigraphiques, pétrologiques, structurales, métamorphiques et géochronologiques. Cette évolution inclut le développement d’un rift continental et l’ouverture de l’océan Rhéïque pendant le Cambro-Ordovicien ainsi que sa fermeture au Dévonien moyen à supérieur. On décrit aussi l’évolution de la convergence et collision varisque entre Laurussia et Gondwana, du début jusqu’aux derniers stades d’un effondrement associé à la perte des racines orogéniques.