| Summary: | In this work, a number of key localities have been investigated in detail in order to provide precise constraints on models for the tectonic evolution of southern Sweden. The new data presented in this thesis show that there are large differences in terms of pre-Sveconorwegian tectonic evolution between the Eastern and Median-Western Segments situated on either side of the Mylonite Zone, a major shear zone as well as a structural and lithological boundary. This has a direct influence on the possible tectonic scenarios that can be suggested when reconstructing the formation of the south-western part of the Fennoscandian Shield. At Viared in the central Eastern Segment, Sveconorwegian eclogite facies metamorphism is dated at 0.97 Ga using mainly U-Pb on zircon. This is similar to other localities showing high-pressure granulite or eclogite facies metamorphism in the Eastern Segment and suggests that this high grade event was a regional feature east of the Mylonite Zone. On the well exposed Nordön Island in the Western Segment, both pre-Sveconorwegian and Sveconorwegian metamorphism and deformation was dated using several isotope methods, including U-Pb SIMS zircon and Sm-Nd garnet dating. In the Median Segment, veining was dated using U-Pb SIMS zircon methods. In addition to age determinations, thermobarometry was done on several samples and the results compared with published data. The results show that Sveconorwegian peak metamorphism reached amphibolite to granulite facies west of the Mylonite Zone at 1.02-1.04 Ga. This is 50-70 Ma before the orogenic activity started in the Eastern Segment. In the central Eastern Segment, Pre-Sveconorwegian veining is dated at 1.42 Ga, thus belonging to the 1.42-1.46 Ga Hallandian veining found elsewhere in the Eastern Segment. Pre-Sveconorwegian veining and isoclinal folding in the Western Segment is dated at 1.55 Ga. Neither the 1.55 Ga nor the 1.02-1.04 Ga events have been found in the Eastern Segment. Further, the 1.42-1.46 Ga veining event documented in the Eastern ...
|
|---|