Exhumation of HT–LP Variscan metapelites from interlayered cordierite–orthoamphibole assemblages (MnNCFMASH System) Catalan Coastal Ranges, NE Iberia

Abstract

Garnet–cordierite–orthoamphibole rocks crop out in centimetric lenses within the pre-Caradocian metapelites of the Osor complex in the sillimanite metamorphic zone of the HT-LP Variscan sequence from the Guilleries Massif in the Catalan Coastal Ranges (NE Iberia). The P– T path followed by the metapelites shows increasing T and P to a peak of 660 °C–5 kbar, then isobaric cooling and finally cooling and decompression. Reaction textures on amphibolite lenses show evidence of resorption of garnet and gedrite and growth of cordierite, anthophyllite and chlorite, which has led to the stable sub-assemblages: garnet + cordierite and gedrite + anthophyllite + cordierite ± chlorite. Petrography, mineral chemistry, and modelling of the low-Ca amphibolite reaction assemblages using a pseudosection approach in MnNCFMASH also suggest a decompressional path when generation of two effective bulk compositional microdomains during cordierite moat formation is taken into account.