Structural analysis of differentiated schists and gneisses in the Taalintehdas area, Kemiö Island, southwest Finland

• Main Authors: P.N.W. Verhoff, E.J.L. Dietworst
• Format: Article
• Language: English
• Published: Geological Society of Finland 1980-12-01
• Series: Bulletin of the Geological Society of Finland
• Online Access: http://www.geologinenseura.fi/bulletin/Volume52/sgs_bt_052_2_pages_147_164.pdf
• ISSN: 0367-5211; 1799-4632

Structural analysis of the Svecokarelic supracrustal schists and gneisses from around Taalintehdas, SW Kemiö Island, SW Finland, has been carried out and a preliminary interpretation is given of the regional structure of Kemiö Island in terms of the fold generations determined in the Taalintehdas area. The first generation of isoclinal folds is established by means of overprinting relationships in the schists. The second generation is marked by tight to isoclinal folds which further transposed earlier layering and foliation. The dominant N70E trending transposition foliation (S2) is openly folded by third generation folds with a N35E trending axial plane crenulation cleavage. Parasitic folds abound in the core of large scale F3 folds; S3 transposition foliation is developed locally. This distinctive tectonic layering is folded by F4 chevron folds with locally developed EW axial plane foliation. The F4 folds are restricted to regions where earlier foliations were oriented NS after the third folding phase. The rocks were metamorphosed under amphibolite facies conditions resulting in the blastesis of sillimanite, andalusite, cordierite and garnet in the schists. The relationship between deformation and metamorphism is discussed.