Gabbroic, doleritic and basaltic xenoliths found in calc-alkali andesites of Naeba and Torikabuto volcanoes are geochemically divided into three groups. Gabbro A of the group 1 from Naeba is rich in MgO and Ni, poor in alkalis, and shows depleted REE pattern resembling those of Ichinomegata (Sp. No. 2232) and Hakone (HKG1, HKG2) volcanoes. On the basis the REE pattern and high Al ^{?? V} contents in clinopyroxenes, gabbro A is interpreted to have been cumulate from a primary magma generated by partial melting of upper mantle. From REE pattern, gabbros of the group 2 from Ichinomegata (Sp. No. 2218) may have derived from low alkali tholeiite magma which have been formed by removal of material such as the group 1 gabbro at shallow depth. Doleritic and basaltic xenoliths of the group 3 from Naeba, gabbroic xenoliths from Torikabuto and Umikawa are poorer in MgO and richer in alkalis than those of the group 1 and show enriched pattern in REE resembling that of high alkali tholeiite and contain clinopyroxenes having low Al ^{?? V}. Therefore, these rocks are considered to be differentiates of high alkali tholeiite magma at shallow depth.
On εNd-⁸⁷Sr/^{8 ??} Sr diagram, isotope data of gabbro A of the group 1 plot near those of andesites from Asama and Myoko volcanoes of the North Fossa Magna. It is interpreted that these rocks have derived from the same mantle source as the Asama and Myoko volcanoes which are richer in incompatible elements than those of MORB.

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Strontium isotope compositions were determined for 1 dacite, 2 low-silica rhyolites, 1 high-silica rhyolite and 2 phenocrystic hornblendes from Hime-shima volcano, Southwest Japan. The whole rocks increase in Rb and ⁸⁷Sr/⁸⁶Sr and decrease in Sr with increasing SiO₂. The high-silica rhyolite composition can be closely reproduced in terms of Rb, Sr and ⁸⁷Sr/⁸⁶Sr by model calculations of assimilation-fractional crystallization of the dacite magma: the material to be assimilated is granodiorite which is presumably spread beneath the volcano. The low-silica rhyolites have compositions close to a mixing line between the dacite and high-silica rhyolite in a Sr-⁸⁷Sr/⁸⁶Sr relation diagram, suggesting that they are mixing products of the dacite and high-silica rhyolite magmas. Hornblende phenocryst and its host dacite have virtually identical ⁸⁷Sr/⁸⁶Sr. On the other hand, hornblende in the low-silica rhyolite has ⁸⁷Sr/⁸⁶Sr between its host rock and the dacite. It is likely that the hornblende was derived from the end-member dacite magma and on the way to be in re-equilibrium with the melt phase of mixed rhyolitic magma when the magma erupted. Because the hornblende in rhyolite shows no sign of re-equilibration with respect to chemical composition, the tracer diffusivility of ⁸⁷Sr/⁸⁶Sr is likely to be higher than the chemical diffusivility.

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Two types of magmas exist at Nishiyama volcano, Hachijojima Island. One is plagioclase-controlled and the other is differentiated magma. The bulk chemistry of the first magma type is controlled by abundance of plagioclase phenocrysts with a constant liquid composition. That of the second type is possibly controlled by fractionation of plagioclase and mafic minerals from a basaltic magma.
Predominant is the plagioclase-controlled basalt at Nishiyama volcano. Summit eruptions invariably tap the plagioclase-controlled magma. Flank eruptions supply not only the plagioclase-controlled basalt, but rarely the differentiated basaltic andesite. These phenomena are similar to those observed at Izu-Oshima volcano. There must be something in common between the magma plumbing systems of Nishiyama and Izu-Oshima volcanoes.

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Some primary ore-textures which are composed of rhodochrosite or caryopilite were observed in manganese ores from the Sagadani mine, where locates in the northern Chichibu Belt, Japan. The rhodochrosite ore shows lenticular form, which consists of spherulites representing cross extinction between crossed nicols. The textures of caryopilite ores are classified to three types. The first is isotoropically massive between crossed nicols, being the most common texture. The second is drop-like in mossaic quartz grains. The drops show homogeneous birefringence without internal textures. The third is a texture resembling peas in a pod or a fine string-like texture, which is inferred to be biogenic origin.
All the textures composed of rhodochrosite or caryopilite are presumed to be formed by diffusion of manganese ions into gelatinous materials of siliceous or muddy sediments.

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