Age of anatexis in the crustal footwall of the Ronda peridotites, S Spain

Antonio Acosta-Vigil*, Daniela Rubatto, Omar Bartoli, Bernardo Cesare, Sandro Meli, Antonio Pedrera, Antonio Azor, Lucie Tajčmanová

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    50 Citations (Scopus)

    Abstract

    This study investigates the age of anatexis of a crustal sequence constituting the footwall of the Ronda peridotite slab, in the hinterland of the Betic Cordillera (S Spain, region of Istán). These rocks represent a polymetamorphic basement involved in the Alpine orogeny and show an increase in the proportion of melt towards the peridotites. Metamorphic conditions in the migmatites vary between T. ≈. 675-750. °C at P. ≈. 0.30-0.35. GPa. The timing of metamorphism and deformation of the migmatites around the Ronda peridotites is controversial and has been previously ascribed to either the Alpine or Variscan orogenies. We present U-Pb SHRIMP dating of zircons from six samples collected across the migmatitic sequence that provide a tighter age constraint on the metamorphism. Zircon ages are related to conditions of metamorphism on the basis of the relationships between zircon microstructures and degree of melting recorded by the host rocks. Anatexis occurred during the late stages of the Variscan orogeny (≈. 280-290. Ma), as indicated by ages of euhedral, oscillatory-zoned domains or new crystals in metatexites and diatexites. Thin, U-rich zircon rims that are affected by radiation damage yield discordant scattered dates between ≈. 260 and 30. Ma, which are interpreted as reflecting a thermal and fluid overprint during the Alpine orogeny that produced recrystallization and Pb loss in Permian zircons. This study identifies a previously unknown Variscan domain within the Betic Cordillera, and indicates, in accordance with previous studies, that Variscan basements recycled during the Alpine orogeny that formed the Betic Cordillera preserve pre-Alpine mineral associations and tectonic fabrics.

    Original languageEnglish
    Pages (from-to)147-167
    Number of pages21
    JournalLithos
    Volume210-211
    DOIs
    Publication statusPublished - 2014

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