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No 10 / 55

The formation of early proterozoic crust in southern Finland : a tentative chronology

Date: 1.1.1990-31.12.1997
Code: K6612
Department: Åbo Akademi University / Faculty of Mathematics and Natural Sciences (MNF), Dept. of Geology and Mineralogy
Address: Domkyrkotorget 1, FIN-20500 Åbo
Phone +358-2-2154 153
Fax +358-2-2154 818
E-mail cehlers@abo.fi
Project leader: FD Carl Ehlers, professor (1.1.1990-31.12.1997)
Researchers: FL Alf Lindroos (1.1.1990-)
Type of research: 0 (0=Within duty, 1=Ordered research, 2=Co-operation)
- basic research 100 %
Man months: Totally: 12 months
Partners: Geologiska forskningscentralen, Esbo, dr Matti Vaasjoki
Contacts: Magma mixing; Pegmatiter i Kimito; Byggnadsstensforskning; IGCO-371
Keywords: jordskorpan, södra Finland, maankuori, Etelä-Suomi, proterozoisk jordskorpa, Svekofennium, södra Finland, plattektoniska modeller, accretionary prism, öbåge, evolution of Proterozoic crust, Svecofennian, southern Finland, plate tectonic models, accretionary prism,

The Svecofennian Proterozoic crust in a 100 km wide and 500 km long zone along the southern coast of Finland shows geochemical and structural features different from those north of the zone.The geochemical signature of the earliest basaltic volcanics have a more oceanic trend contrary to the island-arc type basalts to the north of the zone.Structurally the southern zone shows a higher metamorphic grade and extensive granitic-migmatitic sheets.The earliest structures indicate stacking imricating and overturning of pillowed basalts and chemical sediments together with greywackes/micaschists of continental provenance.The lithologies, geochemistry and structures indicate a different tectonic setting for the southern zone: that of an accretional prism in contrast to the island arc type lithologies further north. -We have compiled a tentative chronological history of the formation of the Svecofennian crust in southern Finland over a period of ~90 million years.

Publication(s)

22.2.1996 / 17.3.1998