Zircon U-Pb geochronology in the Bergen arc eclogites and their Proterozoic protoliths, and implications for the pre-Scandian evolution of the Caledonides in western Norway

The Proterozoic crystalline Lindas nappe of the Bergen are, Caledonides of western Norway, displays local Caledonian eclogite facies overprint along f ractures and shear zones, The overprint results from fluid infiltration in a dry granulite facies protolith under eclogite facies conditions. Formatio n of a low Th/U zircon overgrowth in eclogites is interpreted to be coeval with crystallization of the eclogite facies assemblage. A lower intercept a ge of 456 +/- 7 Ma obtained from combined zircon U-Pb data for an eclogite and an associated granulite are believed to reflect the eclogite facies flu id infiltration event. An alternative minimum age of 419 +/- 4 Ma can be ex tracted from the data. A charnockite and a mafic granulite yield Proterozoi c intrusion ages of 1237 (+43)/(-35),, and 951 +/- 2 Ma, and a garnet-beari ng granulite provides an age of 929 +/- Ma for the late Sveconorwegian gran ulite facies metamorphism, The Proterozoic ages are compatible with a corre lation between the Lindas and Jotun nappes and an origin of the Lindas napp e in the Sveconorwegian province of Baltica, We propose a possible model fe aturing subduction of the Lindas nappe at 456 +/- 7 Ma attached to the Balt ica plate during a Late Ordovician (Caradoc) collision between Baltica and an outboard island are in the lapetus Ocean, Accretion of some of the ophio lite-bearing terranes preserved in the Caledonides of western Norway may ha ve taken plate during this event.