Abyssal tholeiites are found from Tobishima Island in Japan Sea, 40km northwest from Sakata, northeastern Japan. These basalts (Tobishima basalts), including lava flows, minor dikes, epiclastic lapilli tuff and tuff breccia, and hyaloclastite, were formed under water, and overlie acidic volcanic rocks. The basaltic lavas and dikes containing less than 10% of olivine and plagioclase phenocrysts are uniform in composition, but show various degrees of alteration. They are similar to abyssal tholeiites in composition of groundmass augite and coexisting phenocrysts of olivine and plagioclase. In addition, Tobishima basalts plot in the field of abyssal tholeiites in the tectonic discrimination diagrams of FeO^*/MgO-TiO₂, FeO^*/MgO-FeO^*, Y-Zr/Y, Y-Cr, TiO₂-P₂O₅, Ti-Cr and Ti-Ni. The submarine and bimodal character of the volcanism at Tobishima suggests the possibility of Middle Miocene age instead of Early Miocene as was previously deduced from K-Ar dating.

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Oakan is one of the two stratovolcanoes that have grown after the formation of the Akan caldera in eastern Hokkaido. Calcalkaline andesite lavas (53%-64% SiO₂) from the volcano show disequilibrium features resulting from magma mixing, which include reverse zoning of plagioclase and pyroxenes, overgrowth of augite around orthopyroxene, orthopyroxene reaction rims around olivine, and coexistence of olivine and quartz. Inhomogeneous groundmass texture in some lavas reflects an imperfect mixing of magmas. Mafic and felsic inclusions and two types of plagioclase with contrasting glass inclusions probably derived from two mixing endmembers, and underwent either heating or cooling upon mixing.
Two mixing lines are recognized in the Harker diagrams. The mafic endmembers, mafic inclusions of both high and low Ol/Pl ratios, correspond to an unfractionated olivine-rich basalt and a fractionated plagioclase-rich basalt. Felsic endmembers are not found in the lavas, although the magma that produced large-volume pyroclastic flows of Akan caldera is a possible candidate.

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北海道,日高変成帯南西部ニカンベツ複合斑れい岩体中の小さなゼノリスから鉱物集合体からなるサフィリンの仮像が見出された。この仮像は,コランダム+スピネル+緑泥石のコアとパラゴナイト+白雲母+マーガイトからなるリムによって構成され,斜長石とカリ長石により薄く取り巻かれている。
この仮像のコアは,ニカソベツ岩体の下部に存在するグラニュライト相変成岩類からもたらされたゼノリス中の既存のサフィリンが約600°Cで加水分解して形成された。引き続く温度の低下により,一旦形成されたコランダム,スピネルの結晶は約500°Cまでの温度で周囲の斜長石・カリ長石と不完全ながら反応し,その結果として上記三種の雲母からなるリムの形成と緑泥石組成上の再構成がなされた。これらの後退的な反応は,およそ2kbの圧力低下と見積もられ,約100°Cの温度降下を伴う広域的な隆起時期に行われた。

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Field, petrographic and geochemical analyses indicate that the native sulfur at Ras Gemsa is of diagenetic origin. It is formed together with the megacrystalline dolomite (biogenic dolomite) and biogenic calcite by bacterial action on sulfate in the presence of organic matter (hydrocarbons). The sulfur occurs in an uplifted horst block consisting of evaporite-carbonate rocks overlying the Middle Miocene oil and gas bearing strata. The evaporite deposits are interpreted as a composite evaporite sequence which include deposits of shallow lagoonal (subaqueous) as well as supratidal (sabkha) environments.
Two types of dolomites (microcrystalline and megacrystalline are recognized in the studied sequence. Stable isotope data showed that the microcrystalline dolomite are with high values of δ¹⁸O (the mean value is+1‰ PDB) and with relatively low values of δ¹³C (the mean value is -4‰ PDB). These results indicate that the microcrystalline dolomite was deposited mainly under marine evaporitic environment. The megacrystalline dolomite is characterized by negative values of δ¹⁸O (the mean is -6.8‰ PDB) and strongly negative values of δ¹³C (the mean is -23.75‰ PDB). The negative values of δ¹⁸O are probably due to the effect of hot conditions or depleted meteoric water and/or biological effect during dolomite crystallization. Meanwhile, the negative values of ¹³C signify the main role played by the sulfate reducing bacteria in the presence of organic matter.

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LiNiSi₂O₆及びLiTiSi₂O₆スポジュメンを, 60 kb, 1000-1300°Cで,固相反応により合成した。すでに公表されている6種類のLiM³⁺Si₂O₆スポジュメンの格子常数とLiNiSi₂O₆及びLiTiSi₂O₆スポジュメンの格子常数とを比較したところ,スポジュメンの格子常数とM³⁺イオンのイオン半径との関係は,二つの系列に分れる。一方はAl-Fe-Sc-In系列であり,他方はNi-Cr-V-Ti系列である。

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