Mesozoic ophiolite relies in the Southern Steep Belt of the Central Alps

SHRIMP U/Pb age determinations on plagiogranite zircons in the Zone of Bellinzona-Dascio ophiolites yield late Jurassic ages of 149 ± 3 Ma and 142 ± 5 Ma. The plagiogranites are part of a rodingitized and metamorphosed yet well preserved igneous oceanic suite including Mg-gabbros, Fe-Ti-rich gabbros and basalts that is a common feature of the Jurassic Piemont-Ligurian ophiolites. These magmatic ages are among the youngest in this domain and fit well with the observed N-MORB signature of the basalts. The data are indicative of formation in a relatively mature Piemont-Ligurian ocean rather than in an early, embryonic Valaisan ocean.