A4 Article in conference proceedings
Tonalites and similar rocks formed in pre-to syn-collisional stages of the Svecofennian orogeny

List of Authors: Eklund Olav, Jurvanen Terhi, Väisänen Markku
Place: Institute of Seismology, University of Helsinki, Finland
Publication year: 2004
Book title *: Lithosphere 2004
Title of series: Institute of seismology, University of Helsinki, Report S
Number in series: 45
Volume number: 45
ISBN: 951-45-7999-2
ISSN: 0357-3060


Tonalites are the pricipal continent forming rocks. Our preliminary results show that the tonalites in the accretionary arc complex of southern Finland may have been formed by several petrogenetic processes over a period of 80 Ma years (1900 Ma to 1820 Ma).

1) 1900 Ma tonalites and gabbros associated with volcanic rocks of the accretionary arc-complex of

southern Finland. These tonalities can be classified as M-type granitoids.

2) The 1880 Ma Enklinge intrusion is a bimodal tonalite-gabbro intrusion with geochemical character of a typical syn-collisional rock series.

3) In Turku area (and areas in eastern Finland) tonalites evidence an adakitic geochemical signature, that may correspond to melting of a metabasalt at high (15 kbar) pressure. This metabasalt may represent a subducting plate.

4) In some areas of southern Finland melting of amphibolites to tonalities takes place due to high-T low-P regional metamorphism.

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Last updated on 2019-21-08 at 23:28