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The Kawazu (Rendaiji) mine, located in Rendaiji, Shimoda City, Shizuoka Prefecture, Japan (N34°41'40", E138°55'), was once considered to exploit deposits of epithermal Au-Ag-Cu-Mn-Te vein-type. Indium minerals, as well as Bi-, Sn- and Mo-minerals have, however, also been described. The deposits are hosted in Pliocene Suhara andesites (altered andesites, andesitic tuff breccia, tuff, tuffaceous sandstone), basalt dike and rhyolite intrusion. The total metal production from the mine (1915-1962) is 5,357 kg Au, 273 tons Ag, 1,054 tons Cu and 15,840 tons Mn. A K-Ar age determination of 1.36±0.26∼1.53±0.26 Ma was reported by Ministry of International Trading and Industry of Japan (1987). Te(-Se) mineralization is recognized in the Hinokizawa, Ohsawa, Yagiyama, Tsurugamine and Sarukui vein groups where the homogenization temperatures (281-196°C) of fluid inclusions in quartz is higher than those (244-182°C) of other vein groups of the mine. Tellurium-bearing minerals are native tellurium, hessite, cervelleite, petzite, unnamed (Ag,Cu)6TeS2, stuetzite, rickardite, empressite, poubaite, aleksite, tellurobismuthite, tetradymite, kawazulite, calaverite, krennerite, sylvanite, kostovite, goldfieldite (Shimizu and Stanley, 1991) and several secondary minerals. Selenides include bohdanowiczite and paraguanajuatite. Sn-In-Mo mineralization is also limited in the Ohsawa, Yagiyama, Hinokizawa and Sarukui vein groups. Sn-minerals (cassiterite, stannoidite, colusite, nekrasovite), In-minerals (roquesite, dzhalindite) and the Mo-mineral (hemusite (Shimizu et al., 1991)) coexist with Te-Se-bearing minerals. This is the first report on the mode of occurrence of In minerals in the Kawazu mine. Microscopic observation reveals that dzhalindite includes tiny inclusions of Bi-chalcogenides (tellurobismuthite?), and mm-sized dendritic crystals of roquesite occur on dzhalindite, inferring the sequence dzhalindite roquesite with increasing sulfur fugacity. This is in harmony with Sn mineralization described by Shimizu and Shikazono (1987): cassiterite stannite stannoidite mawsonite. In the Ohsawa vein groups, cassiterite is also observed as a precursor of Sn-sulfides, together with In-minerals.
References Ministry of International Trading and Industry, 1987. Report of Regional Geologic Survey, Izu District. 195 pp. (in Japanese) Shimizu, M. and Shikazono, N., 1987. Stannoidite-bearing tin ore: Mineralogy, Texture and physicochemical environment of formation. Canadian Mineralogist, 25, 229-236. Shimizu, M. and Stanley, C. J., 1991. Coupled substitutions in goldfieldite-tetrahedrite minerals from the Iriki mine, Japan. Mineralogical Magazine, 55, 515-519. Shimizu, M., Stanley, C. J., Criddle, A. J., Kato, A. and Matsubara, S., 1991. New compositional and optical data for antimonian and bismuthian varieties of hemusite from Japan. Mineralogy and Petrology, 45, 11-17.
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