Two Tertiary metamorphic events recognized in high‐pressure metapelites of the Nevado‐Filábride Complex (Betic Cordillera, S Spain)

• Published in: Journal of metamorphic geology 2018-06, Vol.36 (5), p.603-630
• Main Authors: Li, Botao, Massonne, Hans‐Joachim
• Format: Article
• Language: English
• Subjects: Betic Cordillera; Carbon dioxide; Composition; Continental margins; Electron microprobe; Electron probes; Eocene; Garnet; garnet zoning; geothermobarometry; Heating; Iron; Isotopes; Metamorphism; Metamorphism (geology); metapelite; Mica; Miocene; Monazite; monazite dating; Orogeny; pseudosection; Ratios; Rock; Rocks; Rutile; Silicon; Stacking; Subduction; Tertiary; Yttrium oxide; Zirconium
• ISSN: 0263-4929; 1525-1314
• DOI: 10.1111/jmg.12312

Two phengite–garnet‐bearing metapelites from the Nevado‐Filábride Complex, Betic Cordillera, one from the Ragua unit (sample 23085) and the other (sample 23098) from the Calar Alto unit, were studied in detail to elucidate their metamorphic evolution. We calculated various P–T pseudosections for different O2 and H2O‐CO2 contents and Fe3+/Fe2+ ratios with PERPLE_X . On the basis of the compositions of the garnet core and the highest Si content in potassic white mica, different peak pressures of 12.7 ± 0.7 kbar at 525 ± 10°C (23085) and 17.4 ± 1.2 kbar at 526 ± 17°C (23098) resulted (errors refer to an estimated 1σ range). The suggested clockwise P–T loop was followed in both cases by another loop caused by a reheating process. On the basis of garnet rim compositions, peak temperatures of 596 ± 10°C at 10.7 ± 1.4 kbar (23085) and 629 ± 11°C at 8.5 ± 0.7 kbar (23098) resulted, supported by Zr‐in‐rutile thermometry (23085: 591 ± 11°C; 23098: 607 ± 10°C). In situ dating of monazite (23085) with the electron microprobe yielded ages between c. 48 and 14 Ma. On the basis of the monazite composition and histogram analysis, two age populations with mean ages of 40.2 ± 1.7 (1σ) and 24.1 ± 0.8 Ma could be defined. Low Y2O3 contents (