Structural and magmatic evolution in the Loimaa area, southwestern Finland
Within the Loimaa area there is a junction of the general E-W structural trend of southern Finland and a NW-N-NE curving trend. The structure of the area is dominated by ductile D3 and D4 deformations with E-W and N-S axial traces, respectively. The typical semicircular structures in the study area...
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| Format: | Article |
| Language: | English |
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Geological Society of Finland
1999-06-01
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| Series: | Bulletin of the Geological Society of Finland |
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| Online Access: | http://www.geologinenseura.fi/bulletin/Volume71/sgs_bt_071_1_pages_057_071.pdf |
| Summary: | Within the Loimaa area there is a junction of the general E-W structural trend of southern Finland and a NW-N-NE curving trend. The structure of the area is dominated by ductile D3 and D4 deformations with E-W and N-S axial traces, respectively. The typical semicircular structures in the study area are interpreted as F3-F4 fold interference structures. The predominant plutonic rocks in the Loimaa area are penetratively foliated tonalites and granodiorites which probably intruded during D2 deformation. Peak regional metamorphism at upper amphibolite facies and emplacement of the Pöytyä Granodiorite ca. 1870 Ma ago occurred during D3 deformation. The ductile style of D4 deformation in the Loimaa area is probably related to the high-grade metamorphism at 1850-1810 Ma in the late Svecofennian granite-migmatite (LSGM) zone immediately south of the study area. The Oripää Granite was emplaced during D4 deformation. The structural evolution in the Loimaa area may be correlated with the evolution further to the northwest (Pori area) and north (Tampere-Vammala area) whereas correlation to the south and west is problematic. A transpressional model presented for the LSGM zone is not applicable to the Loimaa area. |
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| ISSN: | 0367-5211 1799-4632 |