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 69, Issue 3
Displaying 1-4 of 4 articles from this issue
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  • D/H FRACTIONATION OF COEXISTING BIOTITE AND HORNBLENDE IN SOME GRANITIC ROCK MASSES
    YOSHIMASU KURODA, TETSURO SUZUOKI, SADAO MATSUO, SATOSHI KANISAWA
    1974 Volume 69 Issue 3 Pages 95-102
    Published: March 05, 1974
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.69.95
    JOURNAL FREE ACCESS
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    The deuterium content (δDSMOW) of the water extracted from coexisting biotite and hornblende in granitic rocks was measured. The relationship between δD of biotite and hornblende suggested an isotopic equilibrium in the rocks of four granitic bodies in the Kitakami mountains (Northeast Japan), and the maximum temperature of isotopic equilibration of biotite and hornblende was estimated to be 700-1, 000°C, provided that the minimum temperature was 450-550°C. The δD value obtained for the water with which these minerals equilibrated was -29_??_-37‰ and is definitely enriched in deuterium relative to the present local surface water.
    On the other hand, the relationship between δD of biotite and hornblende in the Ryoke metamorphic belt contiguous to the Median Dislocation Line (Southwest Japan) indicated an isotopic disequilibrium. In this case a complicated history of formation of these granitic rocks in terms of the interaction of water and hydrous silicates was inferred.
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  • CRYSTAL FIELD SPECTRA OF DIOPSIDE-KOSMOCHLOR SOLID SOLUTIONS FORMED AT 15Kb PRESSURE
    KO IKEDA, HARUO OHASHI
    1974 Volume 69 Issue 3 Pages 103-109
    Published: March 05, 1974
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.69.103
    JOURNAL FREE ACCESS
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    Diopside-kosmochlor solid solutions have been synthesized at 1 atm and 15Kb and their crystal field spectra have been measured. Solubility is very much increased with pressure and there is only a narrow immiscibility field. The limits of solubility at 1100°C and 15Kb were found to be 19.5 wt percent of kosmochlor molecule in diopside and about 55 wt percent of diopside molecule in kosmochlor, respectively. Crystal field splitting parameter 10Dq and Racah parameter B are nearly constant throughout this solid solution series as expected from their structural analysis.
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  • CHEMICAL COMPOSITION OF FERROMAGNETIC MINERALS IN VOLCANIC ASH LAYERS WITH SPECIAL REFERENCE TO THEIR ORIGINS
    Sadao Shoji, Shinsuke Kobayashi, Jun-ichi Masui
    1974 Volume 69 Issue 3 Pages 110-120
    Published: March 05, 1974
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.69.110
    JOURNAL FREE ACCESS
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    In order to establish the laboratory method to identify volcanic ash layers or to determine their origins, the chemical composition (Fe, Ti, Mn, V, Zn, etc) of ferromagnetic minerals was studied. The ash layers used for this investigation were erupted from Mt. Meakan, Mt. Kamui-nupuri, Mt. Tarumae, Mt. Eniwa, Mt. Zao, Mt. Asama, Mt. Futatsudake and Mt. Daisen.
    The results obtained are as follows;
    1) Compared with Fe and Ti, Mn, V and Zn in ferromagnetic minerals were found to be highly different in the concentration depending on their origins.
    2) Determining the concentrations of various elements in the main minerals separated from volcanic ashes, it was shown that the concentrations of Fe, Ti, V and Zn were the greateat in ferromagnetic minerals, but that of Mn was the greatest in pyroxenes.
    3) In order to lessen the influence of impurities on the relationship between the chemical composition of ferromagnetic minerals and their origins, the weight ratios of V/Fe, Zn/Ti, Mn/Ti, Zn/V, Zn/Fe, etc were examined. It was indicated that the combination of V/Fe-Zn/Ti among the various combinations of the ratios was closely related with the origins and was least influenced by the impurities. On the other hand, the ratios including Mn were considerably changed by the contamination of pyroxenes.
    4) Using Tarumae-a ash layer, recent one erupted from Mt. Tarumae, the chemical composition of ferromagnetic minerals was investigated in relation to the depth of the layer and the distance from the origin. It was found that there was no difference throughout the layer except the bottom and at any distance from the origin.
    From the results mentioned above, it can be concluded that the analysis of the chemical composition of ferromagnetic minerals is highly useful for the identification of volcanic ash layers and for the determination of their origins if it is used together with the stratigraphic results.
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  • FIELD EXCURSIONS ON KIMBERLITES IN SOUTH AFRICA AND LESOTHO
    Ken-ichiro Aoki
    1974 Volume 69 Issue 3 Pages 121-127
    Published: March 05, 1974
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.69.121
    JOURNAL FREE ACCESS
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