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 45, Issue 2
Displaying 1-4 of 4 articles from this issue
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  • Thermal study on some todorokites
    Kokichi Okada
    1961 Volume 45 Issue 2 Pages 49-53
    Published: February 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.49
    JOURNAL FREE ACCESS
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    Todorokite from the manganese one in Fukaura mine, Maruyama mine, Aomori Prefecture, Hongo mine, Iwate Prefecture and Hamayokogawa mine, Nagano Prefecture were studied by means of X ray powder method and differential thermal analysis.
    X ray powder pattern of four specimens in this experiments is corresponded to todorokite from Todoroki mine. D. T. A. curves of todorokite is characterized by a enodothermic peak at 640-660°C, and the endothermic peak is caused by the conversion from todorokite to hausmannite.
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  • Early stage basalts from the Nasu volcanic zone
    Ken-ichiro Aoki
    1961 Volume 45 Issue 2 Pages 54-65
    Published: February 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.54
    JOURNAL FREE ACCESS
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    The early stage basalts of the tholeiite series from the Nasu volcanic zone in northeast Japan are found only in the Funagata volcanic group and are characterized by containing Mg rich pigeonite as phenocrysts. These basalts, showing the chemical composition of typical tholeiite, are notably rich in CaO and very poor in Na2O and k2O as compared with those of the other regions of the world.
    In the tholeiite magma from the Nasu volcanic zone, the order of crystallization and their evolution of mafic minerals are as follows:
    Mg-olivine‾→bronzite-→pigeonite—
    diopsidic augite‾→augite‾→ferroaugite
    The crystallization trends of the pyroxene are similar to that of the Skaergaard intrusion and are unlike that of the pigeonitic rock series (tholeiite series) of the Izu and Hakone districts.
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  • On the augite phenocryst in alkali basalts from the Abu district
    Yoshio Oji
    1961 Volume 45 Issue 2 Pages 66-70
    Published: February 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.66
    JOURNAL FREE ACCESS
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    Two phenocrystic augites in trachybasalts from the Abu district, Yamaguchi prefecture are microscopically and chemically investigated. As a result, it is found that augite from Horikoshi is diopsidic augite expressed by chemical formula
    (Ca0.87Na0.02)0.89(Fe''0.11Fe'''0.06Mg0.90Ti0.01Al0.02)1.10(Si1.92Al0.08)2.00O6.00
    and that augite from Kunigatoge is titanaugite by chemical formula
    (Ca0.85Na0.03)0.88(Fe''0.12Fe'''O.08Mg0.77Ti0.03Al0.08)1.08(Si1.83Al0.17)2.00O6.00
    In the evolution of the clinopyroxene in trachybasalt from this district, the composition of the former augite represents the earliest stage, while the later represents the latest one, so the crystallization trend of clinopyroxene of this district can be assumed parallel to the Di-Hd line within the field of augite-salite as stated by Wilkinson.
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  • On the mineral compositions of “Toraisi” and “Medamaisi”in pyrophyllite ore from the Toyoro Mine
    Morio Amafuji
    1961 Volume 45 Issue 2 Pages 71-78
    Published: February 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.71
    JOURNAL FREE ACCESS
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