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Título:
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Isotopic and geochemical record of the active to passive margin transition in NW Iberia during the Cambrian-Ordovician: vestiges of a waning continental arc
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Autores:
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Andonaegui Moreno, Pilar ;
Díez Fernández, Rubén ;
Abati Gómez, Jacobo
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Tipo de documento:
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texto impreso
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Editorial:
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Springer, 2021
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Dimensiones:
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application/pdf
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Nota general:
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info:eu-repo/semantics/restrictedAccess
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Idiomas:
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Palabras clave:
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Estado = Publicado
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Materia = Ciencias: Geología: Geodinámica
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Materia = Ciencias: Geología: Geoquímica
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Materia = Ciencias: Geología: Petrología
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Tipo = Artículo
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Resumen:
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Time-resolved geochemical data from the orthogneisses of the basal units of the Allochthonous complexes of NW Iberian Massif allow us to track the changes in composition of the magmas generated in a subduction-related setting that affects a continental margin, which evolves from the building of a volcanic arc to its dismantlement during a rifting episode. The basal units are interpreted as a peripheral section of the North African margin of Gondwana and record Neoproterozoic to Cambrian arc-related magmatism, followed by an episode of Cambro-Ordovician rifting. The intrusive rocks of the basal units, preserved as orthogneisses, can be grouped into two magmatic suites: calc-alkaline (c. 493–475 Ma) and alkaline to per-alkaline (c. 475–470 Ma). The calc-alkaline association has a chemical composition ranging from magnesian calcic metaluminous types to ferroan calc-alkalic and alkali-calcic peraluminous types. The moderately alkaline association and per-alkaline metagranites have ferroan alkalic and per-alkaline to metaluminous composition. The chemical characteristics of the metaigneous rocks from the basal units indicate that the older members of the calc-alkaline suite (tonalites and granodiorites) were generated in a continental arc environment, while the alkaline and per-alkaline rocks were formed in an intraplate extensional setting. The negative values in ?Nd (? 7.8 to ? 1.5) of the calc-alkaline suite suggest a crustal influence in its generation. The ?Nd values in the alkaline orthogneisses range between ? 2.0 and 2.2, and are positive in the per-alkaline group, suggesting a greater participation of a mantle component. The transition from the calc-alkaline suite to the alkaline suite is represented by alkali-granites, which are coeval with the intrusion of basic magmas, and likely derived from a mantle magma underplating that triggered the rifting episode after the cessation of continental arc magmatism during the Ordovician.
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En línea:
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https://eprints.ucm.es/id/eprint/64090/1/Isotopic%20and%20geochemical%20record%20of%20the%20active%20to%20passive%20margin%20transition%20in%20NW%20Iberia%20during%20the%20Cambrian-Ordovician.pdf
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