The indium-bearing deposits in the world were reviewd from the geological point of view. This research revealed that the following factors are important for indium concentration in nature, from large-scaled order to smaller one; (1) acid magmatism; (2) ilmenite-series granite; (3) a region in a ilmenite-series district which is established based on the concept of segment; (4) hydrothermal tin-polymetallic deposits (n×10 ² -10 ³ ppm In) and volcano-sedimentary deposits in the continental crust (n×10 ppm In); (5) cauldron for some of the tin-polymetallic deposits; (6) subvolcanic to plutonic condition for tin-polymetallic deposits; (7) certain zone in a tin-polymetallic mine where cassiterite and sulfides (especially bornite) coexist. The geochemical behavior on indium in volcano-sedimentary deposits are not well understood, thus, geologists should study indium of this type of ore, e.g., the specimen from the Kuroko and also from the Okinawa Trough in addition to the research on tin-polymetallic deposits.

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Mineralization at the deeper parts (from -180 to -360 m levels) of the Kaneuchi tungsten deposit in Japan is discussed from the standpoints of Fe/(Fe+Mn) ratios of wolframite, pressure and temperature of ore-forming solutions, and oxygen isotopic compositions of vein quartz.
The Fe/(Fe+Mn) ratios of wolframite from -180 and -300 m levels of the western veins and from -300 m level of the central and eastern veins range from 0.5 to 0.7. Spatial variation of the ratios, including those obtained by the previous work, suggests that the ratios are lower for wolframite occurring nearer to chert.
Using the arsenopyrite-sphalerite geothermometry, temperatures of hydrothermal solutions were obtained to be from 350°to 470°C. Besides this geothermometry, fluid inclusions in vein quartz and scheelite from -180 m to -360 m levels showed the homogenization temperatures ranging from 188° to 365°C, and the averages to be from 252° to 277°C for quartz and from 273° to 290°C for scheelite. Homogenization temperatures suggest that the hydrothermal solution showed a small variation in temperature during the formation of different veins and/or the ascent of solution to higher levels. Corrections of the average homogenization temperatures by the pressure from 1.0 to 1.6 kbar and by the salinities and CO2 concentrations of fluid inclusions lead the temperatures of the hydrothermal solution to be from 300° to 400°C.
Oxygen isotopic compositions of vein quartz from 24 localities are rather constant, ranging from 13.4 to 15.9 per mil relative to SMOW. By using the quartz-water fractionation factors, oxygen isotopic composition of the ore-forming solution is calculated to be from 8.1 to 11.9 per mil at the temperature interval from 350° to 400°C. High δ ¹⁸O values suggest that the ore-forming solution for the Kaneuchi deposit was originated from magmatic fluid or from the fluid interacted with host sedimentary rocks at a low water/rock ratio.

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[in Japanese]

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