Silver minerals from the Sanru mine, which is gold-silver quartz veins of epithermal type, were studied. Veins are consist mainly of banding chalcedonic quartz with small amounts of silver minerals, pyrite, chalcopyrite, sphalerite, arsenopyrite, adularia, kaolinite, sericite and carbonates. As silver minerals in the ore from Honpi and Juji-hi, electrum, aguilarite, naumannite, stephanite, pyrargyrite, miargyrite, polybasite and silver bearing tetrahedrite (freibergite) were determined by ore microscope, electron probe microanalyser and X-ray powder camera.
Electrum is closely associated with naumannite or aguilarite and has chemical compositions from 60.7 to 82.5 atomic % Ag (Table 1). Pyrargyrite occurs as small single grain in quartz vein or aggregate with tetrahedrite and chalcopyrite in veinlets along the crack in quartz vein. Pyrargyrite contains small amounts of Se and As (Table 2), and its chemical composition is very close to ideal formula. Stephanite, miargyrite and polybasite are accompanied by pyrargyrite in quartz vein and their chemical compositions (Table 2) are also very close to their ideal formulae. Tetrahedrite is mainly found in the pyrargyrite-chalcopyrite veinlets cutting quartz vein. It has silver contents from 24.8 to 29.7 wt % (Table 4). Aguilarite and naumannite have chemical compositions from Ag₂Se_0.46S_0.56to Ag₂Se_0.71S_0.29 (Table 5), and form Ag₂Se_0.90S_0.10 to Ag₂Se_0.96S_0.04 (Table 6), respectively.

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Gonnardites found in the altered hydrothermal veins or druses in the Higashi-Matsuura basaltic rocks have cell parameters a=13.45 Å, b=13.42 Å and c=6.67 Å ; the chemical composition determined by Electron probe micro-analyser, (Na, Ca, K)_{3, 62}(Al, Si)_10.05O₂₀•5.47 H₂O. By heating at 350°C for one hour, the mineral turned to amorphous state and by heating at 900°C for one hour, it changed to nepheline, with cell parameters a=9.978 Å and c=8.365 Å (hexagonal system) and chemical composition determined by Electron probe micro-analyser K_0.02Na_4.45(Ca, Mg, Al)_1.18[Si_9.09Al_6.91O₃₂]. The DTA curve shows a large sharp endothermic peak at 345°C and an exsothermic peak at 940°C. The former is due to the dehydration of structural water and the latter to the formation of nepheline. The infra-red absorption spectrum shows absorption bands at 3600, 3400, 1640 and 1000 cm^-1.

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The hydrothermal rock alteration of the Tamagawa Welded Tuff (1.0 to 2.0 Ma in age) which unconformably covers the Neogene Tertiary sediments is studied to assess the geothermal resources in the Hachimantai geothermal field, northern Japan.
The rock alteration is classified into two types; alkaline and acidic alterations. Chlorite zone formed by alkaline alteration is regionally distributed extending NW to SE direction in the central part of the studied areas. Acidic alteration zones characterized by the presence of kaolin, alunite and pyrophyllite, however, are locally distributed around present thermal manifestations such as Toshichi and Takinoue spas.
The distribution of chlorite zone shows the regional activities of alkaline hydrothermal solutions in the Tamagawa Welded Tuff. The remarkable distribution of sericitic minerals within the ehlorite zone at the upper stream area of Kakkondagawa river indicates that the area may have been the center of the alkaline hydrothermal activities related to the volcanism which formed the Tamagawa Welded Tuff.

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The Yakushima granitoids contain 3.1-9.2ppm tin yielding an average of 5.1ppm (n=14), which is slightly higher than that of the Outer Zone granitoids. The tin content of gneissic xenoliths in the granitoids is 4.5 ppm (1.2-9.8 ppm, n=10) in an average, of mafic inclusions is 5.1ppm (3.0-7.5ppm, n=14), and of hornfels is 3.2ppm (2.8-3.5ppm, n=3). Because granitic magmas that bring tin-rich granites may have been originated in tin-rich source materials, then gneissic rocks must be underlain in the studied area underneath the Shimanto Supergroup.

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[in Japanese]

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