STAUROLITE+KYANITE-BEARING PSEUDOMORPHS AFTER ANDALUSITE (CAP DE CREUS, SPAIN)

Pavel Pitra (1) , Francisco Javier Martinez (2)

1 GR - Géosciences Rennes
2 ITA - Instituto Tecnologico de Aragon

Metapelitic rocks from Cap de Creus (Eastern Pyrenees, Spain) have developed andalusite ± cordieritebearing assemblages during the Variscan low-pressure high-temperature metamorphism. Andalusite crystals are commonly transformed to very fine-grained assemblages containing staurolite and kyanite (± chloritoid) together with white micas and biotite. The hydrous character of the replacement minerals (pseudomorphing anhydrous andalusite) and the fact that transformation locally occurs along fractures, suggests that it was enhanced by fluid circulation. Using calculated phase diagrams (pseudosections), the equilibration of the main andalusite-bearing assemblage is constrained at < 4 kbar and 550-600°C. Various types of phase diagrams are combined with a detailed analysis of the crystallisation sequence of the replacement minerals, in order to investigate the conditions of formation of the staurolite + kyanite(±chloritoid)-bearing pseudomorphs. Finally, it is discussed whether the pseudomorphs reflect a “simple” retrograde alteration, a retrogression associated with a pressure increase, or a prograde overprint during another (Pyrenean) orogenic cycle

Domaines: Minéralogie

Pavel Pitra, Francisco Javier Martinez. STAUROLITE+KYANITE-BEARING PSEUDOMORPHS AFTER ANDALUSITE (CAP DE CREUS, SPAIN). 2nd European Mineralogical Conference, Sep 2016, Rimini, Italy. ⟨insu-01378346⟩