The Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists
Online ISSN : 1883-0765
Print ISSN : 0021-4825
ISSN-L : 0021-4825
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Volume 54, Issue 4
Displaying 1-3 of 3 articles from this issue
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  • Occurrence of ferberite from Obanazawa Mine, Yamagata Prefecture, and its significances in the mineralization in the green tuff region
    Tsunehiko Takeuchi, Yushi Funayama, Kazuo Yamaoka, Hiroshi Abe
    1965 Volume 54 Issue 4 Pages 113-126
    Published: October 05, 1965
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.54.113
    JOURNAL FREE ACCESS
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    The Obanazawa mine is situated about 9.5km north-east of Obanazawa City, Yamagata Prefecture, northeastern Japan. The ore deposit is made up of copper-zinc quartz veins developed in dacite and dacitictuff of Miocene age. Ore minerals are chalcopyrite, sphalerite, pyrite, tetrahedrite and ferberite. The pyrite has either pentagonal dodecahedral form or colloform textures. This is the first occurrence of ferberite in the green tuff region of the inner zone of northeastern Japan. Hexagonal; platy crystals of pyrite are observed in the vein found in the Komatazawa valley. It seems that they were crystallized as pyrrhotite single crystals and altered to pyrite aggregates after the formation of the vein. Gangue mineral is quartz accompanied by a small amount of barite. Argillization (mainly sericitization) and silicification are distinguished.
    Ferberite was identified by means of X-ray and chemical analysis; the composition is (Fe0.90 Mn0.10)WO4. Occurrence of ferberite and pyrite after pyrrhotite means that the veins may have formed at high temperature but the properties of other vein minerals suggest that they crystallized at low temperature. They have been explained as a telescoping phenomena of xenothermal type deposits in the greentuff region.
    The Obanazawa mine is situated at the intersection of N-S and NWSE main structural lines of northeastern Japan ; the basement of this area seems to be uplifted. The mineral assemblages of this ore deposit may be explained by assuming that a subvolcanic magma chamber exists in this area.
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  • Pumpellyite in altered basalt of the Hurutobe district, Akita Prefecture
    Mitsuo Shimazu
    1965 Volume 54 Issue 4 Pages 127-131
    Published: October 05, 1965
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.54.127
    JOURNAL FREE ACCESS
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    Pumpellyite was found in altered basaltic rock occurred in Neogene formation of the Hurutobe district, Akita Prefecture.
    The altered basaltic rock is pale grass green to greyish green soft rock and its mode of occurrence is volcanic breccia. Pumpellyite was separated and studied optically and by X-ray powder method. This pumpellyite is fibrous needle and shows pleochroism of pale yellow to brownish yellow. From such pleochroism and high index (γ: 1.744), it seems that the pumpellyite is resemble to golden brown pleochroic mineral (pumpellyite) occurred in the North Range described by Coombs (1953). X-ray powder data consist with that of Calumet pumpellyite (Coombs, 1953). Pumpellyite bearing altered basalt shows the association of pumpelly ite and chlorite-mon-tmorillonite mixed layer mineral and albite.
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  • FELDSPARS IN THE METASOMATIC SYENITIC ROCKS OF SOUTHWESTERN JAPAN
    I. ORDER-DISORDER RELATION IN SOME ALBITIC PLAGIOCLASES
    NOBUHIDE MURAKAMI
    1965 Volume 54 Issue 4 Pages 132-150
    Published: October 05, 1965
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.54.132
    JOURNAL FREE ACCESS
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    [in Japanese]
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