Person: Sánchez Martínez, Sonia
Loading...
First Name
Sonia
Last Name
Sánchez Martínez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Petrología y Geoquímica
Identifiers
6 results
Search Results
Now showing 1 - 6 of 6
Item A peri-Gondwanan arc in NW Iberia I: Isotopic and geochemical constraints on the origin of the arc—A sedimentary approach(Gondwana research, 2010) Fuenlabrada Pérez, José Manuel; Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Díaz García, Florentino; Castiñeiras García, PedroThe arc-derived upper terrane in the NW Iberia Variscan belt contains a 3000 m thick turbiditic formation at its structural top. Most of the sandstones are feldspathic greywackes with a framework of quartz and weakly altered plagioclase. Rock fragments of vitric and microgranular texture are common in polymictic conglomerates and coarse-grained greywackes, together with slates, cherts and bipyramidal volcanic quartz fragments. Although recrystallization under greenschists facies conditions (chlorite and biotite zones) and the presence of two cleavages hinder detailed textural analysis, the sandstones appear to be typically immature, first-cycle sandstones. The metagreywackes have average major and trace element compositions similar to PAAS (Post Archean Australian Shale), which is considered to reflect the composition of the upper continental crust. Their trace element composition is very consistent and records deposition within a convergent tectonic setting, probably in an intra-arc basin located in a volcanic arc built on thinned continental margin. Detrital zircon populations suggest a Middle Cambrian maximum depositional age (530–500 Ma) and a Gondwanan provenance located at the periphery of the West African Craton. Nd isotope data suggest mixing Ediacaran and Paleoproterozoic sources for the provenance of the greywackes, with TDM ranging between 720 and 1215 Ma with an average of 995 Ma (n=20)—an age range unrepresented in the detrital zircon population. The Nd model ages are similar to those exhibited by West Avalonia, Florida or the Carolina terrane, but younger than those of Cambrian and Ordovician sandstones and shales from the autochthonous realm. These data suggest a westernmost location along the Gondwanan margin for the upper terrane of NW Iberia relative to other terranes located in the footwall of the Variscan suture, consistent with several previously proposed paleogeographic models for the NW Iberia terranes.Item Isotope geochemistry and revised geochronology of the Purrido Ophiolite (Cabo Ortegal Complex, NW Iberian Massif): Devonian magmatism with mixed sources and involved Mesoproterozoic basement(Journal of the Geological Society, 2011) Sánchez Martínez, Sonia; Arenas Martín, Ricardo; Gerdex, Axel; Castiñeiras García, Pedro; Potrel, Alain; Fernández Suárez, JavierIn the Purrido Ophiolite (Cabo Ortegal Complex), new U–Pb zircon dating of the amphibolite G03-8 (by laser ablation inductively coupled plasma mass spectrometry) confirms the existence of a dominant Mesoproterozoic zircon population with a refined age of 1155 14 Ma. However, the U–Pb zircon dating of two more amphibolite samples (by sensitive high-resolution ion microprobe) has provided new ages of 395 3 Ma and 395 2 Ma, respectively, interpreted as the crystallization age. Hf isotope data for zircon show that most of the Devonian zircons crystallized from a juvenile depleted mantle source. The Mesoproterozoic zircons have relatively juvenile Hf isotopic composition reflecting some influence of an older component. A few Devonian zircon crystals show evidence of mixing with an older component represented by the Mesoproterozoic zircons. The whole-rock Sm–Nd isotope data indicate an important heterogeneity in the composition of the Purrido amphibolites, only compatible with the generation of their protoliths from two sources. We interpret these puzzling data as resulting from the mixing of a Devonian mantle-derived magma with a Mesoproterozoic basement. These new data provide new perspectives in the interpretation of the most common ophiolites across the Variscan suture in Europe.Item Ophiolites in the Variscan suture of NW Iberia I: Distribution and(Geotemas, 2016) Sánchez Martínez, Sonia; Arenas Martín, RicardoIn the NW Iberian Massif, in the Galicia region, several allochthonous complexes (Cabo Ortegal, Órdenes and Malpica-Tui) contain a rootless Variscan suture that can be followed along the belt. The allochthonous complexes include two different continental terranes and several ophiolitic units sandwiched in between them. Two different ophiolitic belts exist, with different structural position and chronology. The lower ophiolitic units consist of the Bazar and Vila de Cruces ophiolites and are characterized by c. 500 Ma protolith ages. The upper ophiolitic units are composed of the Careón, Purrido and Moeche ophiolites, and contain mafic-ultramafic sequences dated at c. 395 Ma. This younger group represents the most common ophiolites in the Variscan Orogen. Moreover, a thick serpentinite mélange (Somozas Mélange) can also be included among the ophiolitic sequences of the Variscan suture.Item Paleozoic ophiolites in the Variscan suture of Galicia (northwest Spain): Distribution, characteristics, and meaning(4-D Framework of Continental Crust, 2007) Arenas Martín, Ricardo; Martínez Catalán, José Ramón; Sánchez Martínez, Sonia; Díaz García, Florentino; Abati Gómez, Jacobo; Fernández Suárez, Javier; Andonaegui Moreno, María Del Pilar; Gómez Barreiro, Juan; Hatcher, Robert D.; Carlson, Marvin P.; McBride, John H.; Martínez Catalán, José RamónAllochthonous ophiolitic units in the northwestern Iberian Massif are remnants of peri-Gondwanan Paleozoic oceans sandwiched among other exotic terranes of continental and volcanic-arc derivation. All these terranes defi ne an intricate suture zone that marks the convergence and collision between Laurussia and Gondwana. The suture is defi ned by three different ophiolitic ensembles: upper ophiolitic units, lower ophiolitic units, and the Somozas mélange. The lower ophiolitic units were derived from an alternation of basalts and sediments intruded by gabbros and scarce granitoids, and they formed during the opening of a marginal basin, the Galician ocean, during Late Cambrian to Early Ordovician time. This ocean was created as a back arc by the severance of a volcanic arc that had developed at the northern margin of Gondwana and formed part of the Rheic oceanic realm. The upper ophiolitic units formed during the Early Devonian from intraoceanic subduction in the early Paleozoic lithosphere of the Rheic Ocean. These suprasubduction ophiolites were formed just before the ocean closed, preceding the collision between Gondwana and Laurussia. The Somozas mélange appears in an anomalous position at the base of the Cabo Ortegal Complex. The ophiolites involved in this tectonic mélange represent an imbricate of highly dismembered oceanic lithosphere, slivers of subducted outer edge of the Gondwanan continental margin, and Paleozoic metasediments of the northern Gondwanan platform. The ophiolites might either record the development of a different peri-Gondwanan oceanic domain, or they might be equivalent to any of the other ophiolitic ensembles, and their anomalous structural position is simply a consequence of complex thrusting.Item The Calzadilla Ophiolite (SW Iberia) and the Ediacaran fore-arc evolution of the African margin of Gondwana(Gondwana Research, 2018) Arenas Martín, Ricardo; Fernández Suárez, Javier; Montero, Pilar; Díez Fernández, Rubén; Andonaegui Moreno, María Del Pilar; Sánchez Martínez, Sonia; Albert Roper, Richard; Fuenlabrada Pérez, José Manuel; Matas, Jerónimo; Martín Parra, Luis Miguel; Rubio Pascual, Francisco J.; Jiménez Díaz, Alberto; Pereira, M. FranciscoIn the Ossa Morena Domain of SW Iberia, the Calzadilla Ophiolite is formed by an ensemble of ultramafic and mafic rocks that seem to represent a fragment of an oceanic Moho transition zone. The ophiolite consists of a main sheet with a minimum thickness of c. 1000 m and several ultramafic slices that appear imbricated with Ediacaran siliciclastic rocks of the so called Serie Negra. The mafic rocks of the Calzadilla Ophiolite show an extreme depletion in some HFSE such as Nb, Zr, Th, Hf and Ta, low TiO2 contents and high MgO, which allow identifying them as magmatic types of boninitic affinity, such as those frequently associated with fore-arc settings. U-Pb zircon dating of the gabbroic rocks suggests that the igneous protoliths crystallised at c. 600 Ma and were extracted directly from the mantle, according to the juvenile isotopic sources revealed by the Hf isotopic composition of the dated zircons. At c. 540 Ma the U-Pb isotopic system was affected by a partial resetting event with moderate generation of new zircon. According to these data, it is considered that the Calzadilla Ophiolite was formed in a supra-subduction zone setting, very likely in a fore-arc domain, during a roll-back episode affecting the peri-Gondwanan subductive slab. The fore-arc domain was probably proximal to the West Africa Craton. It is very likely that the ductile deformation, metamorphism and tectonic imbrication of the Calzadilla Ophiolite and the Serie Negra occurred at c. 540 Ma, during an increase in the subduction rate and a significant decrease of the subduction angle of the oceanic slab. The information provided by the Calzadilla Ophiolite allows to better constrain the geodynamic evolution of the African margin of Gondwana.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.