Vertical profiles of total sulfur and organic carbon have been measured in two deep-sea piston cores from the Japan Basin of the Japan Sea. The concentration of total sulfur, most of which is present as pyrite, is less than 0.05% in the upper part, while it suddenly increases to 2.0% at certain depths and reachs 5.0 to 4.2% in both cores. The layers with the extremely high sulfur contents are considered to have deposited primarily as a result of the appearance of H₂S-bearing bottom waters. The ¹⁴C ages of the extremely high sulfur layers nearly coincide with the last glacial period.

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Tritium, deuterium and chloride concentrations in the Arima hot spring waters were measured as a clue to their origin and subsurface behavior. T-D-Cl^- relationships clearly indicate that the saline brine of deep origin (T = 0 TR, δD = -30‰ and Cl^- = 43 g/l) is mixed with young meteoric water having T = 30 TR, δD = -50 ‰ and Cl^- = 0g/l in varying proportions to form a group of high chloride hot spring waters. The young meteoric water in a shallow aquifer is also mixed with the older meteoric water in a deeper aquifer characterized by high tritium concentration (∼100TR), forming another group of low chloride waters. The mixing ratio of the two meteoric waters varies with season.

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Chemical compositions of epidote from active and ancient geothermal systems were summarized. Iron and aluminum contents of epidote from geothermal systems vary widely, ranging from about 4 to 19 wt % for Fe₂O₃ and from 18 to 30 wt % for Al₂O₃. It was found that the iron content of epidote has roughly a positive correlation to the Fe₂O₃ content of original rocks, indicating that the Fe₂O₃ content of original rocks affects largely the variations in iron content of epidote. This correlation is consistent with the results of theoretical calculations on the water/rock interaction under the hydrothermal conditions which show that the epidote is formed under the rock-dominated conditions. Epidote associated with hematite has high iron content, while that associated with prehnite, pyrite and pyrrhotite has low iron content. These facts indicate that CO₂ and O₂ fugacities are also important factors controlling the compositional variations in epidote.

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Four K-Ar age determinations were made on the following materials in the Tungsten Province in the Inner Zone of Southwest Japan: biotite from the Koyo hydrothermal replacement Cu veins (Hiroshima Prefecture); sericite-bearing specimens from the Higasa Au-Ag veins (Okayama Prefecture); Okura Cu-Pb-Zn veins (Tottori Prefecture); and Yabu Ag veins (Hyogo Prefecture). They range from 85.1 to 68.9 Ma, which fall within the range reported by SHIBATA and ISHIHARA (1974) for the tungsten deposits in the Tungsten Province. It is pointed out that the base metal mineralization such as associated with copper took place later than the major tungsten mineralization, but somewhat earlier than the precious metal mineralization and the base and precious metal mineralization in and around the well-known Ikuno-Akenobe Province, Hyogo Prefecture.

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Gas components contained in geothermal steams discharged from wells at the Matsukawa geothermal areas were examined geochemically. The original deep seated gases of Northeast Japan are suggested to be uniform with respect to He, Ar and N₂ and are emitted through geothermal wells and/or fumaroles after mixing in various proportions with atmospheric air dissolved in ground water. Geothermal wells of the Matsukawa area are divided into two groups by the geological structure, of the area which controls the variation in concentrations of tritium and major gas components occurs. The influence of the geological barrier can be considered to be limited in a shallow horizon. The correlation between gas components indicates that the reaction, 2NH₃ = N₂ + 3H₂, is in equilibrium, but the reaction, CH₄ + 2H₂O = CO₂ + 4H₂, is not in equilibrium under the condition of the Matsukawa geothermal reservoir.

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K, Rb and Sr concentrations and Sr isotopic composition were determined for eight mafic inclusions found in Cenozoic alkali basalt of the Uta-jima (Uta Island) in the Japan Sea, Southwest Japan. The mafic inclusions are composed of gabbroic and granulitic rocks of presumably lower crustal origin. The mafic inclusions have ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.70457 to 0.70612. Most of them are isotopically distinguishable from the host basalt (0.70360–0.70440), while one mafic inclusion is isotopically indistinguishable from the host, suggesting isotopic exchange. Data for separated minerals from one gabbroic inclusion define a crude isochron, yielding a young age of approximately 100m.y. From the results of the present study and those reported for ultramafic inclusions from the Oki-Dogo Island, another island in the Japan Sea, Southwest Japan, it is inferred that the materials constituting the lowermost crust and the uppermost part of the mantle beneath the Southwest Japan arc have relatively high ⁸⁷Sr/⁸⁶Sr ratios from 0.705 to 0.706 and have relatively young ages.

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Topaz occurs in the central part of the altered zone of the Ugusu mine. Fluorine content of topaz was obrained by X-ray diffraction technique, with an average (±SD) of 19.7 (±0.5) wt%. Based on the assumption that the hydrothermal solution responsible for the formation of topaz has a temperature of 300°C, HF/H₂O activity ratio is estimated to be 10^-1.86. This activity ratio leads to 262ppm as fluoride concentration in hydrothermal solution. Comparison with other acid geothermal waters suggests that fluoride-rich solutions existed during the formation of the topaz. Such a high fluoride concentration may be ascribed to the condensation of volcanic gases.

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