Cambro-Ordovician age of a metagabbro from the Wildschonau ophiolite complex, Greywacke Supergroup (Eastern Alps, Austria): A U-Pb SHRIMP study

The Wildschonau ophiolite complex represents the lowermost and probably oldest rock unit of the western part of the Greywacke Supergroup. Within this ophiolite complex, zircon grains from a metamorphosec gabbro yield a U-Pb SHRIMP age of 477±9 Ma (2σ), interpreted as age of crystallization. This age reflects the magmatic activity in Cambro-Ordovician times and is probably related to a continental rift environment during breakup of Gondwana. The 477±9 Ma age is a few m.y. younger than oldest ages estimated from biostratigraphy; reasons for this difference are evaluated.