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 59, Issue 6
Displaying 1-3 of 3 articles from this issue
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  • Gibbs energy changes of reactions of Mg-Fe distribution and oxidation in coexisting (MgFe)2SiO4 and (MgFe) SiO3, with special references to its petrogenetic significance
    Isamu Shinno
    1968 Volume 59 Issue 6 Pages 217-229
    Published: June 05, 1968
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.59.217
    JOURNAL FREE ACCESS
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    Gibbs energy changes of (Mg-Fe) distribution reaction (12) and oxidation reaction (i), (ii), (iii) are calculated on the basis of thermodynamic constant (Table 2) and experimental data (Table 1, Nafziger et al., 1967). Also it is discussed that the error of Gibbs energy changes calculated from experimental data are smaller than the other from thermodynamic constant. As a result of correspondence between Gibbs energy changes obtained from Nafziger et al. (1967) and calculated from thermodynamic data, the thermodynamic constant used in the calculation may be preferable. For the representaiton of Mg-Fe distribution constant, the equation (2) is more suitable in comparison with the equation (13) because of unity on the consideration of the Gibbs energy changes.
    The stability relations of Fe-oxide and silicate are given in Fig. 2. Fe2SiO4 is more strongly persist to Po2 than FeSiO3 at high temperature but reverse at low temperature. Mg- rich olivine coexisting with Ferich pyroxene in calc-alkaline rock (Fig. 3) may be explained by the above relation.
    Also it is discussed that the Mg-Fe distribution in coexisting olivine and pyroxene may be difficult to discuss simply because of non ideality of these minerals.
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  • K-Ar dating on the alkaline rocks from Nemuro, Hokkaido
    Yoshio Ueda, Ken-ichiro Aoki
    1968 Volume 59 Issue 6 Pages 230-235
    Published: June 05, 1968
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.59.230
    JOURNAL FREE ACCESS
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    In the Nemuro Peninsula in the eastern end of Hokkaido, sheets and lavas of mafic alkaline rocks are abundant. Stratigraphically these alkaline rocks are divided into two stages of igneous activity and are intrusive or extrusive into the Nemuro Formation. From paleontological evidence the Nemuro Formation has been regarded as Late Cretaceous in age.
    The absolute age of six representative samples of the alkaline rocks has been determined by K-Ar dating. The apparent age is as follows: the first stage ranges from 88 to 65m.y. and the second stage, 84 to 67m.y. The least altered sample of the first stage gives 88m.y., and that of the second stage 84m.y. It is, therefore, concluded that the Nemuro Formation and the alkaline rocks were formed at the early stage of the Upper Cretaceous period.
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  • WAIRAKITE FROM HANAWA MINING DISTRICT, NORTHERN JAPAN
    YOTARO SEKI, TADAMITSU TAKAYASU, MIHARU NAKAJIMA, HITOSHI ONUKI
    1968 Volume 59 Issue 6 Pages 236-246
    Published: June 05, 1968
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.59.236
    JOURNAL FREE ACCESS
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    [in Japanese]
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