The geodynamic evolution of garnet-peridotites, garnet-pyroxenites and eclogites of Alpe Arami and Cima di Gagnone (Central Alps) from Early Proterozoic to Oligocene

U-Pb zircon data obtained conventionally and by ionprobe (SHRIMP) demonstrate the polymetamorphic history of the garnet-peridotites at Alpe Arami (Cima Lunga―Adula unit). Partial melting of the periodite immediately followed by high-grade, probably HP-metamorphism occurred at 1.72 Ga. A second event, probably also under HP-metamorphic conditions was Panafrican (ca. 650 Ma) and the present garnet-peridotite/eclogite HP-association was established at 28.5 Ma as derived from SHRIMP-data on zircons from a garnet-peridotite at Cima di Gagnone, also part of the Cima Lunga-Adula unit. This Oligocene age is compatible with the Late Eocene age (35 Ma) for the gabbroic protoliths of the eclogites at Alpe Arami which must also be inferred for the pyroxenitic protoliths of the garnet-pyroxenite veins within the Arami peridotite