北部九州東部に分布する杷木花崗閃緑岩の主成分および微量成分元素測定，U-Pb ジルコン年代測定，希土類元素ならびにSr・Nd 同位体比測定を行った．杷木花崗閃緑岩は，主に斑状の普通角閃石－黒雲母花崗閃緑岩からなり，主岩相と普通角閃石斑状岩相に区分される．本花崗閃緑岩主岩相から106.64 ± 0.82 Ma のU-Pb ジルコン年代が得られた．この年代値は杷木花崗閃緑岩の活動時期を示すと考えられる．本花崗閃緑岩の主成分および微量成分元素組成，希土類元素組成，Sr・Nd 同位体比組成ならびにU-Pb ジルコン年代は，落合花崗閃緑岩と類似する．したがって，杷木花崗閃緑岩と落合花崗閃緑岩は同一のマグマを起源とすると考えられる．
We carried out geological and radiolarian studies in the northern part of the Nishinoomote Formation of the Kumage Group in the South Shimanto Belt, Tanegashima Island. The Nishinoomote Formation in the study area consists mainly of thick bedded sandstone and alternating beds of sandstone and shale with minor amount of varicolored shale. As a result of the radiolarian study, Late Eocene radiolarians such as Lithocyclia ocellus group and Lychnocanium neptunei were obtained from two samples of black shales, and Late Eocene radiolarians such as Lychnocanoma babylonis and Shiphocampe missilis were recognized in one sample of varicolored shale. In the previous study, Early Oligocene radiolarian fossils and calcareous nannofossils had been reported from the northernmost part of the Nishinoomote Formation. Therefore, considering the difference of depositional age and lithology, further study is needed to clarify the relationship between the northernmost part and the northern part of the Nishinoomote Formation.