Mineralogy and petrology of the metasedimentary rocks from the Frido Unit (southern Apennines, Italy)

This work concerns the development of a multidisciplinary research on metasedimentary rocks from the Frido Unit (southern Apennines) in the central Mediterranean area, based on petrographic study, mineralogical analysis and distribution of the major and trace elements. It aims at evaluating the paleoweathering conditions and provenance composition of the source area(s) of both shales and calcschists from the Frido Unit. Shales and calcschists underwent similar HP/LT overprint, by the occurrence of aragonite, as also shown by mineralogical analysis. The mineralogical composition of the studied rocks closely related to the geochemical variations, as shown by the negative correlation of CaO with other elements, due to the dilution effects by the carbonates, and the positive correlation of Al with most of the major and trace elements mainly related to the mica-like clay minerals. Elemental ratios, such as the Chemical Index of Alteration (CIA) and the Index of Compositional Variability (ICV), indicate low to moderate degree of chemical weathering at relatively immature source area(s) and, thus, first-cycle deposits related to tectonically active settings. Furthermore, the distribution of some major and trace elements suggest provenance for the studied samples from source(s) composed of both felsic and mafic rocks.