Meta-andesites in the Caledonides in the Suldal area, Ryfylke.

Abstract

Meta-andesites interlayered with quartz-mica schists, phyllites and tuffites of supposed Cambro-Silurain age cover an area of about 120 km2 in the Suldal area, Ryfylke. Recrystallized meta-andesites are also found in the overlying Gneiss Unit. Petrographical studies and chemical analyses indicate that all these meta-andesites probably belong to the same petrographic province, and that the recrystallization observed in the meta-andesites in the Gneiss Unit is isochemical. These conclusions indicate that most of the Schist Unit (traditionally thought to be of Cambro-Silurian age) and the overlying Gneiss Unit must be regarded as one tectonostratigraphical Unit. The meta-andesites belong to the alkali-calcic series of Peacock, the strong Pacific suite of Rittmann, and the hypersthenic rock series (derived possibly from a high-alumina basalt magma) of Kuno.