Person:
Novo Fernández, Irene

First Name

Irene

Last Name

Novo Fernández

URI

https://hdl.handle.net/20.500.14352/81525

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Mineralogía y Petrología

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Now showing 1 - 8 of 8

Opening and closure of Cadomian peri-Gondwanan oceans: age and evolution of the Mérida Ophiolite (SW Iberia)
(International geology review, 2022) Arenas Martín, Ricardo; Rojo-Pérez, Esther; Díez Fernández, Rubén; Albert, R.; Novo Fernández, Irene; Sánchez Martínez, Sonia; Andonaegui Moreno, María Del Pilar; Moreno Martín, Diana; Gerdes, Axel; Garcia Casco, Antonio
In the SW Iberian Massif, the Ossa-Morena Complex contains a stack of units of different origin and tectonothermal evolution. Individual terranes of the complex record a Cadomian history, traditionally interpreted in relation to the dynamics of a peri-Gondwanan volcanic arc. The interpretation of the Cadomian terranes is a key issue in the reconstruction of the Ediacaran margin of Gondwana in NW Africa. In the Mérida Massif, a mafic – ultramafic unit stacked between two units of continental or arc affinity is interpreted as a Cadomian ophiolite, the Mérida Ophiolite. Within it, mafic lithologies dated at c. 596 Ma (U-Pb in zircon) have calc-alkaline or tholeiitic affinity, indicating generation in a supra-subduction zone setting. The ophiolite shows a main event of Cadomian metamorphism (c. 590 Ma, U-Pb garnet dating) with a prograde P-T path and peak conditions at c. 700°C and 8 kbar. The mafic rocks show Nd isotopic compositions clearly different from those characteristics of the mafic rocks formed in the axial zone of the volcanic arc. Hence, the Mérida Ophiolite probably represents oceanic lithosphere of a back-arc basin, opened between the volcanic arc and the outer margin of Gondwana. Closure of the back-arc occurred during collision of the volcanic arc with the margin of Gondwana (starting at c. 590 Ma), which caused rapid accretion of the back-arc oceanic lithosphere beneath the arc and prograde metamorphism typical of subduction inception. The Mérida Ophiolite was finally obducted above the continental margin of Gondwana, presently preserved in gneissic unit piled beneath the ophiolite. Cadomian evolution of this peri-Gondwanan arc section continued with new tectonothermal events dated in the range 560–540 Ma that alternated with episodes of intense magmatic activity and preceded the collapse of the magmatic arc and its erosive levelling, followed by the generation of a new episode of intense magmatic activity in the arc and the unconformable deposition of the Ediacaran-Cambrian Malcocinado Formation.
Single subduction zone for the generation of Devonian ophiolites and high‐P metamorphic belts of the Variscan Orogen (NW Iberia)
(Terra Nova, 2021) Díez Fernández, Rubén; Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Novo Fernández, Irene; Albert Roper, Richard
Within the Variscan Orogen, Early Devonian and Late Devonian high‐P belts separated by mid‐Devonian ophiolites can be interpreted as having formed in a single subduction zone. Early Devonian convergence nucleated a Laurussia‐dipping subduction zone from an inherited lithospheric neck (peri‐Gondwanan Cambrian back‐arc). Slab‐retreat induced upper plate extension, mantle incursion and lower plate thermal softening, favouring slab‐detachment within the lower plate and diapiric exhumation of deep‐seated rocks through the overlying mantle up to relaminate the upper plate. Upper plate extension produced mid‐Devonian suprasubduction ocean floor spreading (Devonian ophiolites), while further convergence resulted in plate coupling and intraoceanic ophiolite imbrication. Accretion of the remaining Cambrian ocean heralded Late Devonian subduction of inner sections of Gondwana across the same subduction zone and the underthrusting of mainland Gondwana (culmination of NW Iberian allochthonous pile). Oblique convergence favoured lateral plate sliding, and explained the different lateral positions along Gondwana of terranes separated by Palaeozoic ophiolites.
Tracking the Late Devonian high-P metamorphic belt in the Variscan Orogen: New constraints on the PT evolution of eclogites from the Cubito-Moura Unit (SW Iberian Massif)
(Lithos (Oslo. Print), 2021) Novo Fernández, Irene; Arenas Martín, Ricardo; Capitani, Christian de; Pereira, M. Francisco; Díez Fernández, Rubén; Sánchez Martínez, Sonia; Garcia Casco, Antonio
The Cubito-Moura Unit is a high-P metamorphic succession that occurs in the southern part of the Ossa-Morena Complex (SW Iberian Massif). It includes a series of metasedimentary, metafelsic and metamafic rocks affected by a high-P, low to intermediate-T metamorphic event during Late Devonian times. Geochemistry of the metabasic rocks reveals that the generation of the protoliths occurred in a supra-subduction zone setting during Late Ediacaran to Early Ordovician times, either in a back-arc or fore-arc context. The eclogites contain atoll-like garnets, omphacite, amphibole, phengite (up to Si = 3.38 apfu), paragonite, rutile and quartz. Thermodynamic modelling in the MnNCKFMASTH system indicates a high-P metamorphic event at ~24 kbar and ~ 585 °C followed by a thermal peak at ~19 kbar and ~ 630 °C, and a subsequent exhumation to ~15 kbar. This P-T path indicates deep subduction at c. 370 Ma of this arc-related section. The lithostratigraphy and tectonothermal evolution of the Cubito-Moura Unit are equivalent to that of a number of units along the Iberian, Armorican and Bohemian massifs that can be correlated as a part of the same Basal Allochthonous Terrane. These units define a single Late Devonian high-P, low- to intermediate-T metamorphic belt developed during the first stages of the Variscan Orogeny.
Lower Cambrian magmatism in the SW Iberian sector of the African–Gondwana margin: geochemical and isotopic keys to incipient tectonic switching
(Supercontinents, Orogenesis and Magmatism, 2024) Rojo Pérez, Esther; Arenas Martín, Ricardo; Fuenlabrada Pérez, José Manuel; Novo Fernández, Irene; Sánchez Martínez, Sonia; Moreno Martín, Diana; Díez Fernández, Rubén; Nance, R. Damian; Strachan, Robin A.; Quesada Ochoa, Cecilio; Lin, S.
Aspects of the evolution of the Pan-African–Cadomian arc have been recognized in several European massifs. The Ossa–Morena Complex (SW Iberian Massif) is one of the best-preserved sections of this palaeo-Gondwana margin. In this domain, recent studies suggest that arc magmatism followed a cyclical pattern during the Upper Ediacaran and Lower Cambrian. However, its initial and more mature stages remain unclear. Upper Ediacaran magmatism (c. 602 Ma) appears to be uninterrupted and driven by slab–mantle wedge–upper plate interactions. The early Paleozoic was a period of significant change along the Gondwana margin. In the Ossa–Morena Complex, the beginning of the Cambrian (c. 541 Ma) is marked by a strong unconformity over the Ediacaran basement, which is linked to destabilization of the arc. However, subduction-related magmatism continued with increasing mantle input, driving the geochemistry to more alkaline compositions. This paper summarizes the geochemical and isotopic evolution of the peri-Gondwana arc preserved in SW Iberia during this period. These results highlight shifts in geochemistry related to a higher slab angle during each magmatic episode, suggesting a tectonic switch toward an extensional regime in this section of the Gondwana margin.
Reconstruction of the prograde PT history of high‐P migmatitic paragneisses via melt‐reintegration approach and thermodynamic modelling (Allochthonous Complexes, NW Iberian Massif)
(Journal of Metamorphic Geology, 2020) Novo Fernández, Irene; Albert Roper, Richard; Arenas Martín, Ricardo; Garcia Casco, Antonio; Díez Fernández, Rubén; Sánchez Martínez, Sonia
The Upper Units of the allochthonous complexes of the NW Iberian Massif constitute a terrane with continental affinity. They represent the vestiges of a Cambrian magmatic arc developed in the periphery of Gondwana (West African Craton) which was involved in the Devonian Variscan collision, undergoing high‐P, high‐T metamorphism. This includes ultramafic rocks, high‐P mafic rocks (eclogites and granulites) and high‐P migmatitic paragneisses. The latter rocks show an extensive migmatization with the leucosomes oriented parallel to the regional foliation. The migmatitic paragneisses are composed of garnet, kyanite, biotite, quartz, plagioclase, K‐feldspar, rutile and Ti‐hematite. Thermodynamic modelling using the measured bulk composition in the NCKFMASTHO system indicates metamorphic peak conditions of ~15 kbar and ~800 to 835°C, followed by a significant cooling. The prograde evolution is assessed by means of a melt‐reintegration approach, using the composition of the garnet and its inclusions. An appropriate composition of liquid is added to the measured bulk composition to emulate the pre‐melting bulk composition. Modelling of this melt‐reintegrated composition allows to identify a colder high‐P episode below ~500°C. Zircon crystals extracted from the leucosomes show overgrowths crystallized from the partial melt at c. 389 Ma (U–Pb system). The P–T–t path proposed reveals a subduction of the peri‐Gondwanan arc‐derived section down to mantle depths. An isobaric heating stage occurred as a result of residence at great depths and/or inception of a transient oceanic basin at c. 395 Ma. The ensuing near‐isothermal exhumation occurred due to the extension related to the inception of the basin, reaching the thermal peak shortly before c. 389 Ma. Subsequent cooling is related to the underthrusting of colder oceanic and transitional crust below the HP‐HT Upper Units.
Building and collapse of the Cadomian Orogen: A plate-scale model based on structural data from the SW Iberian Massif
(Tectonics, 2023) Moreno Martín, Diana; Díez Fernández, Rubén; Arenas Martín, Ricardo; Rojo Pérez, Esther; Novo Fernández, Irene; Sánchez Martínez, Sonia
The Cadomian Orogeny produced a subduction-related orogen along the periphery of Gondwana and configured the pre-Variscan basement of the Iberian Massif. The architecture of the Cadomian Orogen requires detailed structural analysis for reconstruction because of severe tectonic reworking during the Paleozoic (Variscan cycle). Tectonometamorphic analysis and data compilation in SW Iberia (La Serena Massif, Spain) have allowed the identification of three Cadomian deformation phases and further constrained the global architecture and large-scale processes that contributed to the Ediacaran building and early Paleozoic dismantling of the Cadomian Orogen. The first phase (DC1, prior to 573 Ma) favored tabular morphology in plutons that intruded during the building of a continental arc. The second phase (DC2, 573–535 Ma) produced an upright folding and contributed to further crustal thickening. The third phase of deformation (DC3, ranging between ∼535 and ∼480 Ma) resulted in an orogen-parallel dome with oblique extensional flow. DC1 represents the crustal growth and thickening stage. DC2 is synchronous with a period of crustal thickening that affected most of the Gondwanan periphery, from the most external sections (Cadomian fore-arc) to the inner ones (Cadomian back-arc). We explain DC2 as a consequence of flat subduction, which was followed by a period dominated by crustal extension (DC3) upon roll-back of the lower plate. The Ediacaran construction of the Cadomian Orogen (DC1 and DC2) requires ongoing subduction beneath Gondwana s.l., whereas its dismantlement during the Early Paleozoic is compatible with oblique, sinistral convergence.
A unique blueschist facies metapelite with Mg-rich chloritoid from the Badajoz-Córdoba Unit (SW Iberian Massif): correlation of Late Devonian high-pressure belts along the Variscan Orogen
(International Geology Review, 2021) Arenas Martín, Ricardo; Novo Fernández, Irene; Garcia Casco, Antonio; Díez Fernández, Rubén; Fuenlabrada Pérez, José Manuel; Pereira, Manuel Francisco; Abati Gómez, Jacobo; Sánchez Martínez, Sonia; Rubio Pascual, Francisco J.
The Badajoz-Córdoba Unit (BCU, SW Iberian Massif) is a Variscan high-P unit mainly constituted by metapelites, metagreywackes, orthogneisses, Grt-amphibolites, and retrogressed eclogites (high-P metamorphism at c. 377 Ma). Discovery of rare metapelites with well-preserved high-P mineral assemblages, including large garnets up to 1 cm in diameter with abundant inclusions, chloritoid (up to XMg = 0.32), kyanite, staurolite, chlorite, phengite (up to Si = 3.16 apfu), paragonite, margarite, and rutile, allows detailed determination of the tectonothermal evolution of the unit. Pseudosection modelling of representative samples indicates that this mineral assemblage formed in blueschist facies (near eclogite facies transition) at P conditions higher than 20 kbar at c. 525°C and that it underwent a subsequent severe exhumation and moderate heating. The lithological composition of the BCU, the age of high-P metamorphism and the characteristics of the high-P mineral assemblages are similar to those found in other high-P and low to intermediate-T units of the Variscan Orogen. All these units form part of a single blueschist-eclogite facies metamorphic belt formed during Late Devonian subduction of the external margin of Gondwana.
Cadomia origins: paired Ediacaran ophiolites from the Iberian Massif, the opening and closure record of peri-Gondwanan basins
(Supercontinents, Orogenesis and Magmatism, 2024) Arenas Martín, Ricardo; Vérard, Christian; Albert Roper, Richard; Rojo Pérez, Esther; Sánchez Martínez, Sonia; Novo Fernández, Irene; Moreno Martín, Diana; Gerdes, Axel; Garcia Casco, Antonio; Díez Fernández, Rubén
The recent discovery of Ediacaran ophiolites in the SW Iberian Massif has made it possible to pinpoint the evolution of the Cadomian basement of Europe. The Calzadilla and Mérida ophiolites (gabbroic protoliths dated at c. 600 and 594 Ma, respectively) have geochemical characteristics typical of supra-subduction zone ophiolites. They are interpreted as originating during the initial opening of a forearc basin with boninitic magmatism (Calzadilla), followed by the formation of a back-arc basin with arc-tholeiites (Mérida). Widening of the back-arc led to the rifting and drifting of a section of the active continental margin (Cadomia). Closure of these oceanic domains initiated rapid contraction, culminating in the collision of Cadomia with Gondwana (c. 590–540 Ma). The application of a PANALESIS model to this palaeogeographic setting confirms the plausibility of Cadomian rifting and the likely opening of broad oceanic domains. It also confirms the final collision of Cadomia with Gondwana, although the synthetic and regional data disagree in the precise chronology of the convergence and collision of Cadomia with the West Africa Craton. This work shows that the evolution of the Cadomian basement is much more complex than traditionally considered.