Nature and age of pre-Variscan eclogite protoliths from the Low- to Medium-Grade Metamorphic Complex of north–central Sardinia (Italy) and comparisons with coeval Sardinian eclogites in the northern Gondwana context

摘要: U–Pb zircon data on retrogressed eclogites sampled in the Giuncana locality from Sardinian Medium-Grade Metamorphic Complex yielded a weighted age of 454 ± 6 Ma. This is agreement with ages 453–460 Ma obtained High-Grade Complex. The are very similar to other well-known eclogites. All show positive K, Rb, Ba, U and Pb anomalies negative Nb, La, Ce Sr anomalies. Th depleted enriched those Punta de Li Tulchi Tittinosu. these reveal clear crustal contamination Ordovician mantle. REE patterns typical normal mid-ocean ridge basalt (N-MORB) characterize all supply calc-alkaline materials mantle during further confirmed by fact that most plot left side well above array Th/Yb v. Nb/Yb diagram. In general Variscan framework northern Gondwana, witness recent back-arc basins generated northward opening Rheic Ocean.