Gravity study of the amphibolite syncline in Nagu, SW-Finland

The Korpo—Nagu—Pargas area SW of the town of Turku, SW Finland, can structurally be characterized as a series of more or less closed syncline structures (Fig. 1). The synclines consist of amphibolite, diopside amphibolite and limestone, and the surrounding rock is mainly a migmatic granite (Edelman, 1960). The diopside amphibolites are generally considered to be of sedimentary origin (Metzger, 1945). According to Edelman (1960), volcanism played an important role in the formation of the main part of the amphibolites. The subject of this study, the Nagu syncline, consists mainly of amphibolite rocks which are partly diopside-bearing. Limestone occurs sporadically as thin layers overlying the amphibolite. Concordant micaceous quartz-felspar-gneisses, which are often completely granitized, occur in-