Person: Gómez Barreiro, Juan
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First Name
Juan
Last Name
Gómez Barreiro
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
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Item Using SHRIMP zircon dating to unravel tectonothermal events in arc environments. The early Palaeozoic arc of NW Iberia revisited(Terra nova, 2007) Abati Gómez, Jacobo; Castiñeiras García, Pedro; Arenas Martín, Ricardo; Fernández Suárez, Javier; Gómez Barreiro, Juan; Wooden, Joseph L.Dating of zircon cores and rims from granulites developed in a shear zone provides insights into the complex relationship between magmatism and metamorphism in the deep roots of arc environments. The granulites belong to the uppermost allochthonous terrane of the NW Iberian Massif, which forms part of a Cambro-Ordovician magmatic arc developed in the peri-Gondwanan realm. The obtained zircon ages confirm that voluminous calc-alkaline magmatism peaked around 500 Ma and was shortly followed by granulite facies metamorphism accompanied by deformation at c. 480 Ma, giving a time framework for crustal heating, regional metamorphism, deformation and partial melting, the main processes that control the tectonothermal evolution of arc systems. Traces of this arc can be discontinuously followed in different massifs throughout the European Variscan Belt, and we propose that the uppermost allochthonous units of the NW Iberian Massif, together with the related terranes in Europe, constitute an independent and coherent terrane that drifted away from northern Gondwana prior to the Variscan collisional orogenesis.Item 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, JacoboThe 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.Item Supporting info item, In: "Using SHRIMP zircon dating to unravel tectonothermal events in arc environments. The early Palaeozoic arc of NW Iberia revisited"(Terra nova, 2007) Abati Gómez, Jacobo; Castiñeiras García, Pedro; Arenas Martín, Ricardo; Fernández Suárez, Javier; Gómez Barreiro, Juan; Wooden, Joseph L.Item 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, AliciaOphiolites 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.