The 963 Ma Vinga intrusion and post-compressional deformation in the Sveconorwegian orogen, SW Sweden

In Scandinavia, the 1.15-0.90 Ga Sveconorwegian orogen is transected by maj or N-S trending shear zones separating lithotectonic segments. East of the Oslo Rift, the Idefjorden terrane hosts lithologically distinct, but spatia lly related post-compressional intrusions emplaced along similar WNW trends . The Vinga intrusion yields a 963 +/- 17 Ma age, which combined with ether U-Pb results from this terrane, permits recognition of discrete post-compr essional igneous episodes at 1041-1030, 984, 963, and 920 Ma. After final S veconorwegian convergence and accompanying metamorphism by 969 Ma, gravitat ional collapse and related extension allowed ascent of the Vinga magma into a WNW fracture. We note that extensional movements with a sinistral strike -slip component confined to the N-S trending shear zones that bound the Ide fjorden terrane, provide an emplacement mechanism for post-compressional ma gmas into the resulting WNW-trending fracture system.