The age and origin of the Vaasa migmatite complex revisited
The origin of the Vaasa migmatite complex was studied by using whole-rock Sm-Nd and zircon Lu-Hf and U-Pb data in conjunction with whole-rock major and trace element geochemistry. The concordia ages of five Vaasa area granitoid samples are 1.88–1.86 Ga, constraining the age of peak migmatization. Th...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Geological Society of Finland
2014-06-01
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| Series: | Bulletin of the Geological Society of Finland |
| Subjects: | |
| Online Access: | http://www.geologinenseura.fi/bulletin/Volume86/Bulletin_vol86_1_2014_Suikkanen.pdf |
| Summary: | The origin of the Vaasa migmatite complex was studied by using whole-rock Sm-Nd and zircon Lu-Hf and U-Pb data in conjunction with whole-rock major and trace element geochemistry. The concordia ages of five Vaasa area granitoid samples are 1.88–1.86 Ga, constraining the age of peak migmatization. The ages of inherited zircon cores in the samples show two clear age populations at 2.02–1.92 Ga and c. 2.7 Ga, which correspond to ages yielded by a mica schist sample from the adjacent Evijärvi belt, as well as with published values for the Evijärvi belt zircon. The initial εNd values of the Vaasa complex samples are relatively unradiogenic (from -3.0 to -2.0). Such values are comparable to a value (-3.6) calculated for the Evijärvi mica schist, as well as to literature values (from - 3.0 to -0.5) for the Evijärvi belt. The average initial zircon εHf values of four of the granitoids range from -10 to -5 and are in agreement with the Nd-isotopic results, whereas the northmost sample has a significantly higher value (+1). The deviation is suggested to result from disequilibrium melting of zircon. The isotopic and geochronological data indicate that the Vaasa complex granitoids formed by partial melting of the Evijärvi belt metasedimentary rocks.
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| ISSN: | 0367-5211 1799-4632 |