Characterization of metamorphism in the metapelites of the Bithia Formation, C. Malfatano-Chia Area (Southern Sardinia).

In the considered area, the Infracambrian Bithia Formation structurally overlies Ordovician granitoid gneisses. The age of the metamorphism of all these rocks is Hercynian. This paper presents the main petrographic characters of the Bithia metapelites, as well as data on illite crystallinity and b dimensions of white potassic micas for geothermometric and geobarometric purposes. Illite crystallinity values are anomalous along the structural boundary between the Bithia Formation and the granitoid gneisses, in agreement with the blastomylonitic nature of this boundary, also revealed by field and petrographic evidence.