Studies on the Molybdenum Deposits of the Daito District, Shimane Prefecture, Japan

The molybdenum deposits of the Daito district are located about 20Km southwest of Matsue city, Shimane prefecture, Chugoku province. The deposits under consideration are veins of mesothermal type, and now the most productive deposits of molybdenum in Japan. They are believed to have been formed in close relation to the granites distributed widely in this mining district. Molybdenite and quartz are principal vein minerals, but small amounts of biotite, plagioclase, adularia, epidote, galena, sphalerite, pyrite, calcite, and ankerite are also identified as accessory minerals. Wall-rock alteration is generally remarkable. It is characterized by the presence of an orderly arrangement of silicified zone, sericitized zone, and chloritized zone, from the inner side to the outer side of the ore veins

Hydrothermal Synthesis of Braunite in the Systems MnOOH-SiO₂, Mn₃O₄-SiO₂, and MnO₂-SiO₂

Braunite (MnMn₆SiO₁₂) was synthesized at low temperatures with pressures from 1 to 2500 bar in the systems manganite (γ-MnOOH)-SiO₂, hausmannite (Mn₃O₄)-SiO₂, and pyrolusite (β-MnO₂)-SiO₂. Braunite-pyrolusite assemblage was produced in the first system and braunite-pyroxmangite (MnSiO₃) assemblage in the second system. In the third system, only braunite was formed as solid phase. These reaction equations are as follows. 8MₙOOH+SiO₂=MnMn₆SiO₁₂+MnO₂+4H₂O 3Mn₃O₄+3SiO₂= MnMn₆SiO₁₂+2MnSiO₃ 7MnO₂+SiO₂= MnMn₆SiO₁₂+2O₂ These reaction temperatures, under 1000 bar H₂O total pressure, are 272℃, 459℃, and 521℃ (Po₂=l bar), respectively. P-T diagrams were constructed to show the stability field of braunite. A good correspondence was found between the braunite assemblage synthesized in our laboratory and those observed in bedded manganese ore deposits

マレー西部地域における 2,3 の鉄および錫鉱床について

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