The Ueno basaltic rocks are studied through extensive microprobe analysis of the phenocrysts and a literature survey on the whole-rock analyses. They are olivine tholeiitic to calc-alcalic basalts and andesites erupted at 2.0 ± 0.7 Ma in the East Japan Volcanic Zone in central Japan. Despite their distribution in an island arc system, their magmatic affinity is unlike the arc type: chemical compositions of the phenocrysts (olivine, plagioclase and clinopyroxene) are characteristic to non-arc settings; and the whole-rock analyses do not show marked depletion of Ta, Hf and Ti relative to Th, Ce and Sm. The Ueno basaltic rocks formed probably from the same source as the Neogene alkalic volcanic rocks in west Japan, bearing a within-plate alkalic basalt affinity. The Ueno magmas could be generated by greater degrees of melting of the source at shallower depths.
A model is proposed for the genesis of the Ueno basaltic rocks: a small batch of mantle material, potentially a source of the Neogene alkalic volcanic rocks in west Japan, was drifted to the uppermost mantle beneath central Japan. It is probable that a change in motion of the Philippine Sea plate at 4-2 Ma caused the drift of the non-arc type magma source.

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Oze-Hiuchigatake is a Quaternary composite volcano (<8km³) in northern Kanto, and marks the western end of Nasu volcanic belt. Four stages of activities were found.
(Stage I) Development of a small stratovolcano on the southern part. Effusions of thin andesitic lava flows and intermediate pyroclastic flows intercalated with pumice flows.
(Stage II) Formation of Lake Ozegahara as a result of pumiceous pyroclastic flows. Growth of a composite volcano by 16 andesitic lava flows.
(Stage III) Flank eruptions of thick (<120m) andesite to dacite lava flows and minor pyroclastic flows.
(Stage IV) Effusions of thick dacitic lava flows and growth of three small lava domes at the summit. Collapse of the volcano by debris avalanche on its southwestern foot. Formation of Oze Marsh after the old Nushiri valley was dammed up.

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1500°C, 60 kbarの温度圧力条件で結晶化した, LiAlSi₂O₆-LiGaSi₂O₆系スポジュメン固溶体の格子定数を,粉末法及び単結晶法により測定した。格子定数と化学組成との関係は三つの系列に分れる。これらの結果は, LIGaSi₂O₆スポジュメンが,三種類の異なる構造をとりうることを示唆する。

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