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
7 results
Search Results
Now showing 1 - 7 of 7
Item Geochemistry of the Ediacaran–Early Cambrian transition in Central Iberia: Tectonic setting and isotopic sources(Tectonophysics, 2016) Fuenlabrada Pérez, José Manuel; Pieren Pidal, Agustín Pedro; Díez Fernández, Rubén; Sánchez Martínez, Sonia; Arenas Martín, RicardoA complete Ediacaran–Early Cambrian stratigraphic transition can be observed in the southern part of the Central Iberian Zone (Iberian Massif). Two different stratigraphic units, underlying Ordovician series, display geochemical and Sm–Nd isotopic features in agreement with an evolving geodynamic setting. Pusa Shales (Early Cambrian) rest unconformably on greywackes of the Lower Alcudian Formation (Late Ediacaran). Both sequences present minor compositional variations for major and trace element contents and similar REE patterns, close to those of PAAS (Post Archean Australian Shale). Trace element contents and element ratios suggest mixed sources, with intermediate to felsic igneous contributions for both units. Tectonic setting discrimination diagrams for the Ediacaran greywackes indicate that these turbiditic series were deposited in a sedimentary basin associated with a mature active margin (volcanic arc). However, the compositions of the Cambrian shales fit better with a more stable context, a back-arc or retro-arc setting. εNd(T) and TDM ages are compatible with dominance of a similar cratonic source for both sequences, probably the West Africa Craton. εNd565 values for the Ediacaran greywackes (−3.0 to −1.4) along with TDM ages (1256–1334 Ma) imply a significant contribution of juvenile material, probably derived from the erosion of the volcanic arc. However, εNd530 values in the Cambrian shales (−5.2 to −4.0) together with older TDM ages (1444–1657 Ma), suggest a higher contribution of cratonic isotopic sources, probably derived from erosion of the adjacent mainland. Coeval with the progressive cessation of arc volcanism along the peri-Gondwanan realm during the Cambrian, there was a period of more tectonic stability and increasing arrival of sediments from cratonic areas. The geochemistry of the Ediacaran–Cambrian transition in Central Iberia documents a tectonic switch in the periphery of Gondwana, from an active margin to a more stable context related to the onset of a passive margin.Item Tectonic evolution of Variscan Iberia: Gondwana–Laurussia collision revisited(Earth-Science Reviews, 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, JerónimoAn integrated interpretation of the late Paleozoic structural and geochronological record of the Iberian Massif is presented and discussed under the perspective of a Gondwana-Laurussia collision giving way to the Variscan orogen. Compressional and extensional structures developed during the building of the Variscan orogenic crust of Iberia are linked together into major tectonic events operating at lithosphere scale. A review of the tectonometamorphic and magmatic evolution of the Iberian Massif reveals backs and forths in the overall convergence between Gondwana and Laurussia during the amalgamation of Pangea in late Paleozoic times. Stages dominated by lithosphere compression are characterized by subduction, both oceanic and continental, development of magmatic arcs, (over- and under-) thrusting of continental lithosphere, and folding. Variscan convergence resulted in the eventual transference of a large allochthonous set of peri-Gondwanan terranes, the Iberian Allochthon, onto the Gondwana mainland. The Iberian Allochthon bears the imprint of previous interaction between Gondwana and Laurussia, including their juxtaposition after the closure of the Rheic Ocean in Lower Devonian times. Stages governed by lithosphere extension are featured by the opening of two short-lived oceanic basins that dissected previous Variscan orogenic crust, first in the Lower-Middle Devonian, following the closure of the Rheic Ocean, and then in the early Carboniferous, following the emplacement of the peri-Gondwanan allochthon. An additional, major intra-orogenic extensional event in the early-middle Carboniferous dismembered the Iberian Allochthon into individual thrust stacks separated by extensional faults and domes. Lateral tectonics played an important role through the Variscan orogenesis, especially during the creation of new tectonic blocks separated by intracontinental strike-slip shear zones in the late stages of continental convergence.Item Geochemistry and tectonostratigraphy of the basal allochthonous units of SW Iberia (Évora Massif, Portugal): Keys to the reconstruction of pre-Pangean paleogeography in southern Europe(Lithos, 2017) Díez Fernández, Rubén; Fuenlabrada Pérez, José Manuel; Chichorro, Martim; Pereira, M. Francisco; Sánchez Martínez, Sonia; Silva, José B.; Arenas Martín, RicardoThe basal allochthonous units of NW and SW Iberia are members of an intra-Gondwana suture zone that spreadsacross the Iberian Massif and was formed during the collision of Gondwana and Laurussia in the late Paleozoic. This suture zone is made of allochthonous terranes and is currently preserved as a tectonically dismembered ensemble. A multi-proxy analysis is applied to the basal allochthonous units of Iberia to test their affinity and potential usage for tracing a suture zone. A comparison of the lithostratigraphy, tectonometamorphic evolution, geochronology, and geochemical characteristics of the Ediacaran series of these units reveals striking affinities. They derive from rather similar immature sedimentary successions, deposited along the same continental margin, and in relation to a Cadomian magmatic arc. Sm–Nd systematics indicates that the isotopic sources are among the oldest of the Iberian Massif (ca. 2.15–1.5 Ga), suggesting a very strong contribution from the West African Craton. These Ediacaran series were affected by high-P and low- to medium-T metamorphism (blueschist to eclogite facies) during the Late Devonian (ca. 370 Ma). They occur below allochthonous ophiolitic sequences, and on top of autochthonous or parautochthonous domains lacking of high-P and low- to medium-T Devonian metamorphism, i.e., tectonically sandwiched between lithosphere-scale thrusts. The combination of all these characteristics makes these particular Ediacaran series different from the rest of the terranes of the Iberian Massif. Such singularity could be useful for tracing more occurrences of the same suture zone along the Variscan orogen, particularly in cases where its preservation and recognition may be cryptic. It also contributes to improve the paleogeographic reconstruction of the margin of Gondwana during the Ediacaran.Item Ediacaran to Cambrian oceanic rocks of the Gondwana margin and their tectonic interpretation(International Journal of Earth Sciences, 2015) Raumer, Jürgen F. von; Stampfli, Gérard Maurice; Arenas Martín, Ricardo; Sánchez Martínez, SoniaIn tectonic maps of Variscan Europe, allochthonous pieces of Cadomian basement clearly stand out with their predominant metabasic to ultrabasic elements, the so-called exotic terranes with ophiolites. Most of these domains are observed in basements of the Central Iberian Allochthone, the South Armorican domain, the nappe structures of the French Massif Central, the Saxothuringian Zone and the Bohemian Massif. Similar relics can be recognized in many Alpine basement areas, and correlations with supposedly more autochthonous basements, such as the Ossa Morena Zone and the Central Iberian basement, can be envisaged. All of these relics are thought to represent the interrupted trace of a former continuous or discontinuous structure, characterized by the presence of ocean-derived proto-Rheic rock suites. These can be interpreted as pieces of former magmatic arcs of Ediacaran to Cambrian age accreted to the Gondwana margin, which later were scattered as allochthonous units during the Variscan plate-tectonic processes. The presence of similar rock suites of Ordovician age in the Alpine realm is explained by the accretion of exotic China-derived basements and their collision with the Gondwana margin during the opening of the Rheic Ocean.Item The last stages of the Avalonian–Cadomian arc in NW Iberian Massif: isotopic and igneous record for a long-lived peri-Gondwanan magmatic arc(Tectonophysics, 2016) Andonaegui Moreno, María Del Pilar; Arenas Martín, Ricardo; Albert Roper, Richard; Sánchez Martínez, Sonia; Díez Fernández, Rubén; Gerdes, AxelThe upper allochthonous units of NW Iberian Massif contain an extensive Cambrian magmatism (c. 500 Ma), covering felsic to mafic compositions. The magmatic activity generated large massifs of granitoids and gabbros, with calc-alkaline and tholeiitic compositions respectively. Petrological and geochemical features of these massifs are characteristic of volcanic arc. The plutons intruded siliciclastic sedimentary series deposited in the periphery of the West Africa Craton. U–Pb/Hf isotopic compositions of detrital zircon in the siliciclastic host series, indicate continental arc activity between c. 750 Ma and c. 500 Ma. It was characterized by a large variety of isotopic sources, including from very old continental input, even Archean, to the addition of a significant amount of juvenile mafic material. These isotopic sources experienced an extensive mixing that explains the composition and isotopic features (εHft from −50 until +15) of the represented Cambrian plutons. The Cambrian igneous rocks of the upper units of NW Iberia are related to the latest activity of the Avalonian–Cadomian arc. From the Middle Cambrian arc activity in the periphery of Gondwana was replaced by pronounced extension associated with the development of continental rifting, which finally led to separation of the microcontinent Avalonia. Subsequent drifting of Avalonia to the North caused progressive opening one of the main Paleozoic ocean, the Rheic Ocean.Item Allochthonous terranes involved in the Variscan suture of NW Iberia: A review of their origin and tectonothermal evolution(Earth-Science Reviews, 2016) Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Díez Fernández, Rubén; Gerdes, Axel; Abati Gómez, Jacobo; Fernández Suárez, Javier; Andonaegui Moreno, María Del Pilar; González Cuadra, Pablo; López Carmona, Alicia; Albert Roper, Richard; Fuenlabrada Pérez, José Manuel; Rubio Pascual, Francisco J.NW Iberia includes a rather complete section of a Variscan suture, where different terranes with continental or oceanic affinities appear with clear structural relationships. Three groups of terranes, namely Upper, Ophiolitic and Basal units and a frontal tectonic mélange appear in Galicia, in Cabo Ortegal, Órdenes and Malpica-Tui complexes. They constitute a huge allochthonous pile thrust over the Iberian parautochthonous and autochthonous domains, which represent the section of the Gondwanan margin that escaped continental subduction during the Variscan cycle. Considering the allochthonous character of the nappe pile and the strong deformation associated to the Variscan collision, there are problems to identify the original tectonic setting of the terranes and thence, it is difficult to reconstruct the paleogeographic context during the Variscan and pre-Variscan times in detail. Key features to perform any model for the Variscan convergence should consider the existence of two different high-P metamorphic events (dated at c. 400 and 370 Ma, respectively), separated in time for the generation of mafic-ultramafic sequences at c. 395 Ma which constitute the most common ophiolites described in the Variscan suture. Some dynamic models developed in NW Iberia have important problems to explain the observed tectonothermal evolution, especially the older high-P metamorphic event and the exhumation of deeply subducted transitional-type sections. On the other hand, the recently discovered participation of an older continental crust in the generation of different protoliths of the Middle Devonian ophiolites, makes difficult the interpretation of these ophiolites in relation to open wide oceanic domains. This paper describes the distribution, structure, lithologies, geochronology and chemical composition of the terranes involved in the Variscan suture of NW Spain. The scope of this description ranges from detailed regional aspects to the discussion of the development of the Variscan Orogen in the context of the assembly of Pangea. A two-stage collisional model affecting a wide Gondwanan platform may explain most of the evidences in NW Iberia. The generation of a long pull-apart basin probably occurred after the first collision, where the Devonian ophiolites were formed. These ophiolites have been in general described in the context of the Rheic Ocean, but according to the new existing data they do not seem related to this ocean, but rather they were formed after its closure.Item The Galicia–Ossa-Morena Zone: Proposal for a new zone of the IberianMassif. Variscan implications(Tectonophysics, 2016) Arenas Martín, Ricardo; Díez Fernández, Rubén; Rubio Pascual, Francisco J.; Sánchez Martínez, Sonia; Martín Parra, Luis Miguel; Matas, Jerónimo; González del Tánago y del Río, José; Jiménez Díaz, Alberto; Fuenlabrada Pérez, José Manuel; Andonaegui Moreno, María Del Pilar; Garcia Casco, AntonioCorrelation of a group of allochthonous terranes (referred to as basal, ophiolitic and upper units) exposed in theNW and SW of the Iberian Massif, is used to propose a new geotectonic zone in the southern branch of theVariscan Orogen: the Galicia–Ossa-Morena Zone. Recent advances in SW Iberia identify most of the formerOssa-Morena Zone as another allochthonous complex of the Iberian Massif, the Ossa-Morena Complex, equiva-lent to the Cabo Ortegal, Órdenes, Malpica-Tui, Bragança and Morais complexes described in NW Iberia. Thenew geotectonic zone and its counterparts along the rest of the Variscan Orogen constitute an Internal VariscanZone with ophiolites and units affected by high-P metamorphism. The Galicia–Ossa-Morena Zone includes aVariscan suture and pieces of continental crust bearing the imprint of Ediacaran–Cambrian events related tothe activity of peri-Gondwanan magmatic arcs (Cadomian orogenesis). In the Iberian Massif, the general struc-ture of this geotectonic zone represents a duplication of the Gondwanan platform, the outboard sections beingjuxtaposed on top of domains located closer to the mainland before amalgamation. This interpretation offersan explanation that overcomes some issues regarding the differences between the stratigraphic and paleontolog-ical record of the central and southern sections of the Iberian Massif. Also, equivalent structural relationships be-tween other major geotectonic domains of the rest of the Variscan Orogen are consistent with our interpretationand allow suspecting similar configurations along strike of the orogen. A number of issues may be put forward inthis respect that potentially open new lines of thinking about the architecture of the Variscan Orogen.