Person: Abati Gómez, Jacobo
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First Name
Jacobo
Last Name
Abati Gómez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Petrología y Geoquímica
Identifiers
4 results
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Item U–Pb evidence for a polyorogenic evolution of the HP–HT units of the NW Iberian Massif(Contributions to mineralogy and petrology, 2002) Fernández Suárez, Javier; Corfu, Fernando; Arenas Martín, Ricardo; Marcos Vallaure, Alberto; Martínez Catalán, José Ramón; Díaz García, Florentino; Abati Gómez, Jacobo; Fernández Rodríguez, Francisco JoséA isotope dilution thermal ionisation mass spectrometry U–Pb geochronological study was carried out on the high-pressure and high-temperature units (HP–HT units) overlyingthe oceanic suture in the Allochthonous Complexes of the NW Iberian Variscan Belt. The rocks investigated are seven granulite- to eclogitefacies paragneisses and one leucosome within mafic highpressure granulites in the Ordenes and Cabo Ortegal Complexes of NW Spain. U–Pb datingof zircon, monazite, titanite and rutile reveal the presence of a pervasive Early Ordovician metamorphic event at ca. 500–480Ma and a later Early Devonian event at ca. 400–380 Ma. The U–Pb ages, in conjunction with petrological and structural data, indicate that the high-pressure event recorded by these rocks is Early Ordovician in age. Monazite ages in the paragneisses suggest that peak metamorphic conditions were reached at ca. 500–485Ma. Subsequently, the rock ensemble underwent exhumation accompanied by partial meltingan d zircon growth at ca. 485–470Ma. Meltingof mafic granulites was coeval with this latter episode as indicated by zircon crystallisation age in the leucosomes dated at ca. 486 Ma. Based on these data and on the general features of magmatism and metamorphic evolution, it is proposed that this process took place at a convergent plate boundary within a peri-Gondwanan oceanic domain. Monazite, titanite and rutile data in some of the samples studied show evidence of a second metamorphic episode that took place between ca. 400 and 380 Ma (with a peak at ca. 390–385Ma). This Early Devonian event, at variance with the previous one, was not pervasive, but, rather, was localised in areas of intense Variscan tectonothermal reworking. It is claimed that this later metamorphic event was recorded by the U–Pb system in areas where monazite and titanite growth was enhanced by fluid circulation in highly strained rocks (Variscan shear zones). Accordingto previous structural studies and Ar–Ar datingof fabrics, this Early Devonian episode took place as the HP–HT units were deformed and thrusted upon the ophiolitic units in the early stages of the Variscan collision.Item Variscan accretionary complex of northwest Iberia: Terrane correlation and succession of tectonothermal events(Geology (Boulder Colo.), 1997) Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Díaz García, Florentino; Abati Gómez, JacoboThe allochthonous terranes of northwest Iberia can be correlated with specific paleogeographic realms of the continental masses and intervening oceans involved in the Variscan collision. Assuming that the existing ophiolites represent the suture formed by the closure of the Rheic ocean, the units in the footwall to the suture correspond to the outer edge of the Gondwana continental margin, and the units in the hanging wall are interpreted as fragments of the conjugate margin, represented by the Meguma terrane. This correlation establishes a precise link between circum-Atlantic terranes, and makes it possible to draw a relatively simple scenario of the successive tectonothermal events recorded. Following the amalgamation of Avalon to Laurentia, the remaining outboard terranes underwent a progressive accretion to this continent that ended with the collision between Laurentia and Gondwana.Item Constraints on the provenance of the uppermost allochthonous terrane of the NW Iberian Massif: inferences from detrital zircon U–Pb ages(Terra nova, 2003) Fernández Suárez, Javier; Díaz García, Florentino; Jeffries, Teresa E.; Arenas Martín, Ricardo; Abati Gómez, JacoboInsight into the origin and pre-orogenic palaeogeographical links of terranes involved in the assembly of collisional mountain belts is fundamental to the understanding of orogenic processes. Here we address the provenance and possible tectonic settings of the uppermost allochthonous terrane of the NW Iberian Variscan Belt through a 213-nm Laser Ablation ICP-MS study of U–Pb ages of detrital zircons. The age groups of zircons from greywackes in this terrane (c. 480–610, 1900–2100, 2400–2500 Ma) and the lack of Mesoproterozoic zircons suggest an origin in a Neoproterozoic – Early Palaeozoic peri- Gondwanan realm along the periphery of the west African craton. It is further inferred that the greywackes were deposited in the periphery of a crustal unit that had been detached from the Gondwanan margin in relation to the opening of the Rheic ocean in Cambro-Ordovician times. This terrane was thrusted back upon the Gondwanan margin during the course of the Variscan collision and closure of the intervening ocean.Item Tectonic evolution of a continental subduction‐exhumation channel: Variscan structure of the basal allochthonous units in NW Spain(Tectonics, 2011) Díez Fernández, Rubén; Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Abati Gómez, JacoboA regional study starting from detailed geological mapping has been carried out in the Malpica‐Tui Complex of Galicia in NW Spain. The complex is formed by two units representing pieces of the external edge of Gondwana, subducted and exhumed during the Variscan collision. The study shows that synsubduction and early synexhumation structures in continental subduction channels tends to be obscured and even erased once exhumation is complete. Detailed structural analysis, matched with the knowledge of the history, and available data for other Galician basal units have elucidated the major structures developed during the subduction‐exhumation process. The results include evidence of the plate convergence causing early Variscan continental subduction of the Gondwana margin. Subduction was followed by exhumation driven by ductile thrusting within the subduction channel, which, in turn, provoked crustal duplication in the subducted slab and modified the initial tectonometamorphic architecture of the subduction wedge. The next step was accretion to the adjacent continental domains, placing the subduction wedge on top of unsubducted parts of the Gondwana margin via ductile thrusting. Thrusting was preceded by progressive propagation of a train of recumbent folds toward the foreland that affected the previous structural stack. Subsequent transference of oceanic (Rheic) and peri‐Gondwanan terranes to the Gondwana margin took place by out‐of‐sequence thrusting followed by crustal extensional collapse and strike‐slip tectonics