Layering in rapakivi granite, SW Finland

oleh: C. Ehlers

Format: Article
Diterbitkan: Geological Society of Finland 1974-12-01

Deskripsi

Layering in rapakivi granite occurs locally in the islet Söderören, Åland, SW Finland. The layering consists of 3—5 cm thick, rhythmically repeated layers with high concentrations of biotite, hornblende, allanite and olivine. Almost all layers are asymmetric with sharp lower contacts but gradually pass-ng into the overlying light layers. Many layers show cross-cutting structures resembling current bedding in sedimentary rocks. It is concluded that the layering is a gravity stratification probably due to convective magmatic currents in the roof zone of a granitic magma.