Palaeoproterozoic structural evolution of polyphase migmatites in Olkiluoto, SW Finland
In migmatitic environments the behaviour of the system is controlled by the generation and amount of the anatectic melt. Accordingly, migmatites typically show a genetic linkage between the tectonic deformation and melt migration. We investigated this relationship in Olkiluoto (SW Finland) and id...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Geological Society of Finland
2022-11-01
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| Series: | Bulletin of the Geological Society of Finland |
| Subjects: | |
| Online Access: | https://www.geologinenseura.fi/sites/geologinenseura.fi/files/engstrom_et_al_bulletin_vol_94_part_2_119_144.pdf |
| Summary: | In migmatitic environments the behaviour of the system is controlled by the generation
and amount of the anatectic melt. Accordingly, migmatites typically show a genetic
linkage between the tectonic deformation and melt migration. We investigated this
relationship in Olkiluoto (SW Finland) and identified four phases of ductile deformation,
which are distinguished by the multiple folding phases, ductile shear events and
cross-cutting features associated with pegmatitic leucosomes and/or a specific type
of diatexitic migmatite with feldspar megacrysts. U–Pb LA-MC-ICPMS data on zircon
cores and rims from migmatites and cross-cutting pegmatites indicate two distinct
metamorphic events associated with melt generation and migration at 1.87–1.84 Ga
and 1.82–1.78 Ga. These two migmatitic events suggest that the orogenic evolution of
the area was long-lasting and characterized by slow cooling. The structural data and the
age constraints presented in this paper support the idea of similar tectonic evolution
and metamorphic environment in SW Finland and central E Sweden. |
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| ISSN: | 0367-5211 1799-4632 |