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 11

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.
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.
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.
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.
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.
Unraveling the origins and P-T-t evolution of the allochthonous Sobrado unit (Órdenes Complex, NW Spain) using combined U–Pb titanite, monazite and zircon geochronology and rare-earth element (REE) geochemistry
(Solid Earth and Discussions, 2020) Benítez Pérez, José Manuel; Castiñeiras García, Pedro; Gómez Barreiro, Juan; Martínez Catalán, José Ramón; Kylander-Clark, Andrew; Holdsworth, Robert
The Sobrado unit, within the upper part of the Órdenes Complex (NW Spain) represents an allochthonous tectonic slice of exhumed high-grade metamorphic rocks formed during a complex sequence of orogenic processes in the middle to lower crust. In order to constrain those processes, U–Pb geochronology and rare-earth element (REE) analyses of accessory minerals in migmatitic paragneiss (monazite, zircon) and mylonitic amphibolites (titanite) were conducted using laser ablation split stream inductively coupled plasma mass spectrometry (LASS-ICP-MS). The youngest metamorphic zircon age obtained coincides with a Middle Devonian concordia monazite age (∼380 Ma) and is interpreted to represent the minimum age of the Sobrado high-P granulite facies metamorphism that occurred during the early stages of the Variscan orogeny. Metamorphic titanite from the mylonitic amphibolites yield a Late Devonian age (∼365 Ma) and track the progressive exhumation of the Sobrado unit. In zircon, cathodoluminescence images and REE analyses allow two aliquots with different origins in the paragneiss to be distinguished. An Early Ordovician age (∼490 Ma) was obtained for metamorphic zircons, although with a large dispersion, related to the evolution of the rock. This age is considered to mark the onset of granulite facies metamorphism in the Sobrado unit under intermediate-P conditions, and related to intrusive magmatism and coeval burial in a magmatic arc setting. A maximum depositional age for the Sobrado unit is established in the late Cambrian (∼511 Ma). The zircon dataset also record several inherited populations. The youngest cogenetic set of zircons yields crystallization ages of 546 and 526 Ma which are thought to be related to the peri-Gondwanan magmatic arc. The additional presence of inherited zircons older than 1000 Ma is interpreted as suggesting a West African Craton provenance.
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.
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.