Person:
Sánchez Martínez, Sonia

First Name

Sonia

Last Name

Sánchez Martínez

URI

https://hdl.handle.net/20.500.14352/75196

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Mineralogía y Petrología

Area

Petrología y Geoquímica

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Now showing 1 - 10 of 56

Sm–Nd isotope geochemistry and tectonic setting of the metasedimentary rocks from the basal allochthonous units of NW Iberia (Variscan suture, Galicia)
(Lithos (Oslo. Print), 2012) Fuenlabrada Pérez, José Manuel; Arenas Martín, Ricardo; Díez Fernández, Rubén; Sánchez Martínez, Sonia; Abati Gómez, Jacobo; López Carmona, Alicia
The basal units of the allochthonous complexes of NW Iberia are formed by thick metasedimentary rock sequences intruded by granitoids, ranging in composition from calc-alkaline (c. 493 Ma) to minor alkaline– peralkaline massifs (c. 475–470 Ma), and mafic rocks. The granitoids were transformed into variably deformed othogneisses and the associated mafic rocks were transformed into amphibolites, blueschists and eclogites during eo-Variscan high-P metamorphism dated at c. 370 Ma. Two different superimposed metasedimentary rock sequences can be distinguished. The lower sequence (maximum depositional age at c. 560 Ma) is mainly composed of metagreywackes, while the upper sequence (maximum depositional age at c. 500 Ma) consists of mica schists and other minor types. Major and trace element geochemistry of the metagreywackes of the lower sequence suggests that they were generated in relation to a peri-Gondwanan arc system built on the thinned continental margin, although some chemical transition to passive margin greywackes is also observed. This sedimentary sequence was probably deposited in an Ediacaran–Early Cambrian back-arc setting or retro-arc setting, closer to the thinned platform of the continental margin. The geochemical features of the sedimentary rocks of the upper sequence suggest some affinity with passive margin sediments; they were probably deposited closer to the continental domain and to certain distance from the most active zones of the magmatic arc. The Nd model ages of 23 analysed samples are Paleoproterozoic and range between 1782 Ma and 2223 Ma (average value 1919 Ma). The Nd model ages are slightly younger in the upper sequence than in the lower sequence, but altogether they define a single population, and therefore the two metasedimentary rock sequences can be clearly related. Sedimentation probably took place within the same basin located in the continental platform of Gondwana, the main source areas of these sedimentary rocks did not change during the Late Neoproterozoic and Cambrian times. The Nd model ages are very old and they seem to be compatible with Paleoproterozoic or Archean source areas, with only minor participation of younger sources probably represented by intrusive Cadomian–Pan-African granitoids.
Two-stage collision: Exploring the birth of Pangea in the Variscan terranes.
(Gondwana research, 2014) Arenas Martín, Ricardo; Díez Fernández, Rubén; Sánchez Martínez, Sonia; Gerdes, Axel; Fernández Suárez, Javier; Albert Roper, Richard
The Variscan suture exposed in NW Iberia contains a stack of terranes including two allochthonous units with continental affinity and Gondwanan provenance (Upper and Basal Units), separated by an ophiolite belt where the most common units show protolith ages at c. 395 Ma. Recent Lu–Hf zircon data obtained from these ophiolites indicate interaction between the gabbroic magmas and old continental crust. Hence, the ophiolites could not have originated in a deep ocean basin associated with a mature mid-ocean-ridge or intraoceanic subduction. The tectonothermal evolution of the continental terranes bounding the suture zone records two consecutive events of deep subduction. The Upper Units record an initial high-P/ultra-high-P metamorphic event that occurred before 400–390 Ma, while the Basal Units were affected by a second high-P/low-to-intermediate-T metamorphic event dated at c. 370 Ma. Continental subduction affected the most external margin of Gondwana and developed in a setting of dextral convergencewith Laurussia. Development of the two high-P events alternated with the opening of an ephemeral oceanic basin, probably of pull-apart type, in Early Devonian times. This ephemeral oceanic domain is suggested as the setting for the protoliths of the most common ophiolites involved in the Variscan suture. Current ideas for the assembly of Pangea advocate a single collisional event between Gondwana and Laurussia in the Carboniferous. However, the new evidence from the allochthonous terranes of the Variscan belt suggests a more complex scenario for the assembly of the supercontinent, with an interaction between the colliding continental margins that started earlier and lasted longer than previously considered. Based onmodern analogs of continental interaction, the development of complex collisions, as here suggested for Gondwana and Laurussia during the assembly of Pangea, could have been the norm rather than the exception throughout Earth history.
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.
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.
Evolución tectónica del Macizo Ibérico durante la orogenia Varisca: colisión Gondwana - Laurrusia
(Geotemas, 2016) Díez Fernández, Rubén; Arenas Martín, Ricardo; Pereira, M. Francisco; Sánchez Martínez, Sonia; Albert Roper, Richard; Martín Parra, Luis Miguel; Rubio Pascual, Francisco J.; Matas, J.
La revisión de la evolución tectonometamórfica y magmática del Macizo Ibérico revela periodos de extensión y convergencia alternantes dentro de un proceso global de convergencia entre Gondwana y Laurrusia durante la formación de Pangea en el Paleozoico Superior. Fases dominadas por compresión a escala litosférica se caracterizan por el desarrollo de subducción oceánica y continental, generación de arcos magmáticos, cabalgamientos y procesos de acreción de litosfera continental y plegamiento. Eventualmente, la convergencia Varisca durante el Carbonífero produjo la transferencia de un conjunto de terrenos alóctonos peri-Gondwánicos, el denominado Alóctono Ibérico, sobre Gondwana. El Alóctono Ibérico muestra una impronta tectonometamórfica previa a ese proceso de transferencia fruto de la yuxtaposición temprana de Gondwana y Laurrusia tras el cierre del océano Reico en el Devónico Inferior. Las fases dominadas por fenómenos extensionales están representadas por la apertura de dos cuencas oceánicas efímeras a expensas de la corteza orogénica formada hasta el momento, primero en el Devónico Inferior-Medio, tras el cierre del Reico, y luego durante el Carbonífero Inferior, tras el emplazamiento del alóctono peri-Gondwánico. Seguidamente, un evento de extensión intra-orogénica durante el Carbonífero Inferior-Medio desmembró al Alóctono Ibérico en apilamientos individuales de unidades exóticas separados por fallas extensionales y domos. La tectónica transcurrente jugó un papel fundamental durante toda la orogenia Varisca, especialmente durante la creación de nuevos bloques tectónicos separados por zonas de cizalla transcurrentes intra-continentales en las últimas etapas de convergencia continental.
The Bazar Ophiolite of NW Iberia: a relic of the Iapetus–Tornquist Ocean in the Variscan suture
(Terra nova, 2012) Sánchez Martínez, Sonia; Gerdex, Axel; Arenas Martín, Ricardo; Abati Gómez, Jacobo
The Bazar Ophiolite, one of the ophiolitic units involved in the Variscan suture of NW Iberia, is mainly formed by metagabbroic high T amphibolites with N-MORB affinity. The ophiolite appears accreted under an arc-derived upper terrane affected by intermediate-P granulite facies metamorphism dated at 496– 484 Ma. U-Th-Pb geochronology and Lu-Yb-Hf isotope geochemistry of zircons allow recognizing two growth stages. The first occurred during crystallization of the gabbroic protolith and has been dated at 495 ± 2 Ma, whereas the second one, interpreted as dating the high T metamorphism, yielded an age of 475 ± 2 Ma. The chronology of the Bazar Ophiolite and its accretionary history suggest that this unit is a relic of the Cambrian ocean located to the North of Gondwana, the Iapetus–Tornquist Ocean, accreted to a dissected arc during or before the early stages in the opening of the Rheic Ocean.
Paleogeografía geoquímica de las series metasedimentarias del Macizo Ibérico
(Geotemas, 2016) Fuenlabrada Pérez, José Manuel; Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Díez Fernández, Rubén; Pieren Pidal, Agustín Pedro
Las características geoquímicas e isotópicas de las series turbidíticas del Macizo Ibérico reflejan distintos escenarios tectónicos en la periferia de Gondwana. Estos cambios se observan en el registro sedimentario de la transición Ediacarense-Cámbrico, que tuvo lugar en el contexto general de un margen continental activo. TDM jóvenes y ɛNd menos negativos resultan característicos de cuencas sedimentarias más exteriores, con una importante contribución de material juvenil derivado del sector más activo del arco volcánico (metagrauvacas culminantes de las Unidades Superiores del Complejo de Órdenes). Las cuencas sedimentarias más próximas al continente se caracterizan por mayores aportes desde dominios alejados del arco activo que dan lugar a valores de TDM más antiguos y ɛNd muy negativos (metagrauvacas de las Unidades Basales del Complejo de Malpica-Tui). Una evolución desde contextos activos hasta otros más propios de márgenes pasivos se detecta con claridad en la transición Ediacarense-Cámbrico, y debe relacionarse con una disminución de la actividad del arco volcánico y la transición hacia un margen pasivo. El diagrama de fSm/Nd vs ɛNd confirma esta variación de los escenarios tectónicos asociados al margen de Gondwana, perfectamente registrados en los metasedimentos de diferentes sectores y unidades del Macizo Ibérico.
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.
From Rodinia to Pangaea: Ophiolites from NW Iberia as witness for a long-lived continental margin
(Special publication - Geological Society of London, 2009) Sánchez Martínez, Sonia; Arenas Martín, Ricardo; Fernández Suárez, Javier; Jeffries, Teresa E.
The ophiolites preserved in the Variscan suture of NW Iberia (Galicia) show a broad variability in lithology, geochemistry and chronology. This wide variety rules out the simplest plate tectonic scenario in which these ophiolites would have been exclusively related to the oceanic domain closed during the final Pangaea assembly, that is the Rheic Ocean. The ophiolitic units from Galicia also provide important data about the palaeogeography immediately preceding the opening of this ocean, and some information about pre-Gondwanan supercontinent cycles. Six different ophiolites can be distinguished in the allochthonous complexes of Galicia: the Purrido, Somozas, Bazar, Vila de Cruces, Moeche and Careón units. The Purrido Ophiolite is constituted by metagabbroic amphibolites with igneous protoliths dated at 1159 ± 39 Ma (Mesoproterozoic), and geochemical affinities typical of island-arc tholeiites. These mafic rocks can be interpreted as one of the scarce members of the pre-Rodinian ophiolites, and they were probably generated in a back-arc setting in the periphery of the West African Craton. The Somozas Ophiolitic Mélange consists of a mixing of submarine volcanic rocks (pillow-lavas, submarine breccias, pillow-breccias, hyaloclastites), diabases, gabbros, microgabbros, diorites and granitoids, surrounded by a matrix of serpentinites or, less frequently, phyllites. Two granitic samples from this mélange yield U-Pb ages ranging between c. 527 and 503 Ma (Cambrian), which together with the characteristic arc signatures obtained in all the studied igneous rocks suggest that this ophiolite was generated in a peri-Gondwanan volcanic arc. The Bazar Ophiolite is formed by different tectonic slices with high temperature amphibolites, granulites, metagabbros and ultramafic rocks. The amphibolites are the most abundant rock type and show typical N-MORB compositions with igneous protoliths dated at 498 ± 2 Ma (Cambrian). The high-temperature metamorphism affecting some parts of the unit has been dated at c. 480 Ma (lower Ordovician), and it is considered to be related to the development of an oceanic accretionary complex under the volcanic arc represented by the upper units of the allochthonous complexes of Galicia. Considering the most common palaeogeographic reconstructions for the Cambrian period, it is suggested that the oceanic lithosphere represented by the Bazar Ophiolite was formed into the peri-Gondwanan oceanic domain prior to the rifting of the Avalonian microcontinent, that is the Iapetus-Tornquist Ocean. According to current data about the Vila de Cruces Unit, it can be interpreted as a composite terrane, whose lithologies have U-Pb ages ranging from 1176-497 Ma, but constituted by metaigneous rocks with arc signatures. This dataset has been interpreted in relation to the development of a back-arc basin around the Cambrian-Ordovician limit, involving a Mesoproterozoic basement and the reactivation of a former suture. The opening of this back-arc basin can also be identified as the birth of the Rheic Ocean, and probably it would also include the lithological succession belonging to the Moeche Unit, although its basic rocks exhibit compositions with more oceanic character. Finally, the Careón Ophiolite includes remnants of an oceanic lithosphere generated in a supra-subduction zone setting at 395 ± 2 Ma (middle Devonian). This ophiolite was formed in a contractive Rheic Ocean, shortly preceding the closure of this ocean. This is the only ophiolite in Galicia that can be related to mature stages of the Rheic Ocean, although as it is commonly observed in other regions the N-MORB crust is not preserved. This common oceanic crust has disappeared during subduction, probably in an intra-oceanic setting and during the generation of the igneous section preserved in the Careón Ophiolite.
A Peri-Gondwanan arc active in Cambrian-Ordovician times: the evidence of the uppermost terrane of NW Iberia
(2011) Arenas Martín, Ricardo; Abati Gómez, Jacobo; Sánchez Martínez, Sonia; Andonaegui Moreno, María Del Pilar; Fuenlabrada Pérez, José Manuel; Fernández Suárez, Javier; González Cuadra, P.; Gutiérrez-Marco, Juan Carlos; Rábano, Isabel; García-Bellido, Diego