Blueschist metamorphism of metabasite dykes in the serpentinites of the Frido Unit, Pollino Massif

Salvatore Laurita (a) & Giovanna Rizzo (a)
(a) Dipartimento di Scienze, Università degli Studi della Basilicata, 85100-Potenza Corresponding author e-mail: giovanna.rizzo@unibas.it

Metamorphic evolution of metabasite dykes included in tectonic slices of serpentinites in ophiolitic rocks from Frido Unit (Pollino Massif) is reported. Petrological analysis via PT pseudo-sections calculation using Theriak-Domino software have been done for the system Na₂O-CaOK₂O-MgO-FeO-Al₂O₃SiO₂-H₂O (NCKMFASH) and showed that the pressure and temperature conditions of blueschist metamorphism are estimated to 8-12 kbar and 300-400 °C. The minerals in the metabasite dykes are chemically homogeneous, suggesting that they are almost completely equilibrated. The retrograde metamorphic evolution of the metabasites from high- to intermediate-pressure conditions is documented by the occurrence of minerals belonging to pumpellyite facies assemblages. High-pressure metamorphism in blueschist facies condition is related to the subduction of Frido Unit in low gradient conditions. The use of pseudosections stepwise controlled by petrographic observations allowed to estimate the P-T conditions in metabasite dykes.

metabasites, blueschist facies, southern Apennines, pseudo-section.