Petrology and ion microprobe U-Pb chronology applied to a metabasic intrusion in southern Sweden: A study on zircon formation during metamorphism and deformation

摘要

The Aker metabasite occupies a key position in a major tectonic lineament in southernmost Sweden, the Protogine Zone, which coincides closely with the eastern boundary of the late Mesoproterozoic Sveconorwegian orogen of southwest Scandinavia. Metamorphic reactions, associated with the transformation from isotropic gabbro to foliated garnet amphibolite, were identified from disequilibrium textures of which some involved release of zirconium (Zr) and growth of metamorphic zircon. Ion microprobe dating of igneous zircon gave 1562 +- 6 Ma, whereas metamorphic zircons yielded ages of 1437+-21, 1217+-75, and 1006+-68 Ma.