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

Abstract

In Scandinavia, the 1.15-0.90 Ga Sveconorwegian orogen is transected by major N-S trending shear zones separating lithotectonic segments. East of the Oslo Rift, the Idefjorden terrane hosts lithologically distinct, but spatially related post-compressional intrusions emplaced along similar WNW trends. The Vinga intrusion yields a 963±17 Ma age, which combined with other U-Pb results from this terrane, permits recognition of discrete post-compressional igneous episodes at 1041-1030, 984, 963, and 920 Ma. After final Sveconorwegian convergence and accompanying metamorphism by 969 Ma, gravitational 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 Idefjorden terrane, provide an emplacement mechanism for post-compressional magmas into the resulting WNW-trending fracture system.

Keywords:

• U-Pb geochronology
• zircon
• hybrid intrusion
• Sveconorwegian
• late-orogenic
• post-compressional deformation
• Idefjorden terrane
• SW Sweden