Lithogeochemistry of metabasites from the Moura Phyllonitic Complex (Ossa Morena Zone, SW Portugal)

Abstract

The Moura Phyllonitic Complex (MPC) is interpreted as a tectonic mélange that extends along the Montemor - Ficalho sector, overlaying the Relative Autochthone of the Ossa Morena Zone (Iberian Variscides, SW Portugal). Its northern boundary with the Estremoz-Barrancos sector is demarked by the Sto. Aleixo da Restauração Thrust. Generally, the MPC comprises several sericitic-chloritic and siliceous metasedimentary and metavolcanic rocks in a sheared matrix with unknown age, possible ranging from Cambrian to lower Devonian. Frequent imbrications of mafic suites with tholeiitic affinities are known within the MPC: obduction-related sequences, HP metamorphic rocks and dismembered volcanics interpreted as parautochthonous imbrications variably metamorphosed from lower-medium grade greenschist to amphibolite facies. Several of these metabasites were sampled for major and trace element ICP-OES analysis (prepared with alkaline fusion, acid digestion and cation-exchange chromatography), in order to characterize their geochemical variability and attempt to correlate with other autochthonous volcanic rocks, thus inferring their geodynamic setting.