下北半島，於法岳火山の岩石記載とK-Ar年代

抄録

Oho-dake volcano, situated at the central part of the Shimokita peninsula, Northeast Japan, is a small Quaternary composite volcano consisting of coexisting tholeiitic and calc-alkaline andesitic to dacitic lavas and pyroclastic flow deposits. Two K-Ar ages (1.99±0.08Ma and 2.03±0.08Ma) were obtained from the uppermost part and lower part of lava flows, which overlap within the estimated errors. Small volume eruptions of Oho-dake volcano are consistent with small and short-lived magma batches within the magma plumbing system.