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 23

Preferred orientation of anorthite deformed experimentally in Newtonian creep
(Earth and planetary science letters, 2007) Gómez Barreiro, Juan; Lonardelli, I.; Wenk, H.-R; Dresen, G.; Rybacki, E.; Ren, Y.; Tomé, C.N.
Synthetic anorthite aggregates were deformed in a Paterson gas deformation apparatus at confining pressures up to 400 MPa in torsion and axial compression at temperatures between 950 °C and 1200 °C. Samples deformed in torsion under Newtonian creep display development of texture (or crystallographic preferred orientation) as documented with synchrotron X-ray diffraction measurements. Complex diffraction patterns were deconvoluted with the Rietveld method to obtain quantitative texture information. Torsion samples deformed up to shear strains of 4 and samples deformed in compression at higher stresses to total strains of 0.3 develop clear textures. Texture and shape preferred orientation (SPO) of torsion samples display a monoclinic pattern with an asymmetry inclined against the sense of shear, consistent with polycrystal plasticity simulations that assume the deformation is accomplished by dislocation glide. These results show that a material deforming in linear-viscous creep can develop a strong texture, in striking contrast to the paradigm that the presence of a texture precludes low-stress Newtonian behavior. Our observations show that the presence or absence of crystallographic preferred orientation is not sufficient to uniquely infer the dominant rheological/mechanical regime, as sometimes applied for interpretation of seismic anisotropy in the Earth.
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.
Age constraints on Lower Paleozoic convection system: Magmatic events in the NW Iberian Gondwana margin
(Gondwana research, 2012) Díez Fernández, Rubén; Castiñeiras García, Pedro; Gómez Barreiro, Juan
The basal units of the allochthonous complexes of NW Iberia are used to examine the Lower Paleozoic geodynamic evolution of the northern Gondwana margin. These units represent the most external continental margin and the sequence of major magmatic events that affected them has been dated. Isotopic dating and field data highlight the existence of two magmatic pulses, dated at 489±4 Ma (granodiorites) and 474±3 Ma (alkali-granites), and a slightly younger alkaline/peralkaline pulse, dated at ca. 470–475 Ma (alkaline and peralkaline granites). Their framing into the regional background has allowed us to explore the major lithosphere-scale processes developed at the Gondwana periphery at that time, as well as to conceive a consistent model for the opening of the Rheic Ocean that reconciles the timing of sea opening and back-arc extension with the timing of intracontinental rifting. The sequence of events is framed in a Cambrian and Ordovician peri-Gondwanan subduction setting where we also explore how subduction may be linked to coeval intraplate magmatism far inboard of the arc–trench. This contribution discusses how such a scenario can be traced in basement areas through a modern analog perspective.
The late Variscan HT/LP metamorphic event in NW and Central Iberia: relationships to crustal thickening, extension, orocline development and crustal evolution
(Geological Society, London, special publications, 2014) Martínez Catalán, José R.; Rubio Pascual, Francisco J.; Díez Montes, Alejandro; Díez Fernández, Rubén; Gómez Barreiro, Juan; Dias Da Silva, Ícaro; González Clavijo, Emilio; Ayarza, Puy; Alcock, James E.; Schulmann, K.
The Variscan metamorphic evolution of the autochthonous domain of NW and Central Iberia is characterized by a Barrovian gradient followed by a high-temperature–low-pressure (HT/LP) event associated with voluminous granite magmatism. The structural, metamorphic and magmatic histories of the region are described briefly and the relations between them are explained. A coherent model for evolution of the continental crust is proposed using published radiometric ages, thermal models and seismic reflection profiles. The metamorphic evolution, including the high-temperature event, is explained by crustal thickening resulting from the Gondwana–Laurussia collision followed by a period of thermal relaxation and a long-lasting extensional stage. The fact that the highest temperatures were reached in the core of the Central Iberian arc, partly occupied by remnants of a huge allochthonous nappe stack, is discussed in relation to both the emplacement of the allochthon and subsequent oroclinal bending. The overburden provided by the allochthonous pile was decisive in triggering the high-temperature event. Orocline development mostly occurred later and had no significant effect on the metamorphic evolution, although it was important for the present localization of gneiss domes and granitoids. The possible role of the mantle in supplying additional heat to explain the HT/LP event is also discussed. It would seem that little mantle contribution was needed and there are no strong arguments for mantle delamination, although some kind of mantle–crust interaction is expected beneath the hot regions presently occupying the core of the Central Iberian arc.
Basal slip and texture development in calcite: new results from torsion experiments
(Physics and chemistry of minerals, 2007) Barber, D.J.; Wenk, H.-R.; Gómez Barreiro, Juan; Rybacki, E.; Dresen, G.
The deformation behavior of calcite has been of longstanding interest. Through experiments on single crystals, deformation mechanisms were established such as mechanical twinning on e = {1018} 〉404〉 in the positive sense and slip on r = {1014} 〉2021〉 and f = {1012} 〉0221〉 both in the negative sense. More recently it was observed that at higher temperatures f{1012} 〉1011〉 slip in both senses becomes active and, based on slip line analysis, it was suggested that c(0001) 〉1120〉 slip may occur. So far there had been no direct evidence for basal slip, which is the dominant system in dolomite. With new torsion experiments on calcite single crystals at 900 K and transmission electron microscopy, this study identifies (0001) 〉1120〉 slip unambiguously by direct imaging of dislocations and diffraction contrast analysis. Including this slip system in polycrystal plasticity simulations, enigmatic texture patterns observed in compression and torsion of calcite rocks at high temperature can now be explained, resolving a long-standing puzzle.
Modelo petrogenético de las mineralizaciones de Sn-W asociadas al domo de Martinamor (Salamanca): planteamiento del problema
(Macla, 2022) Ortega Menor, Lorena; Bermejo López, Daniel; Castiñeiras García, Pedro; Crespo Feo, María Elena; Barrios Sánchez, Santos; Gómez Barreiro, Juan
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.