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 65, Issue 4
Displaying 1-3 of 3 articles from this issue
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  • On the Orikabe granitic body, Kitakami mountainland
    Masami Ishijima, Yuzo Kato
    1971 Volume 65 Issue 4 Pages 149-161
    Published: April 05, 1971
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.65.149
    JOURNAL FREE ACCESS
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    The Orikabe granitic body, Kitakami mountainland, intruded in middle-upper Cretaceous, is studied petrographically. From field and microscopic observations, this body is divided into three rock types of Sasamori, Orikabe and Tokusenjo. The Sasamori type is the most leucocratic of the three and contains no pyroxenes. The Orikabe type rocks carry pyroxenes always rimmed by amphibole (hornblende with or without cummingtonite) and a small amount of biotite. The Tokusenjo type is melanocratic and contains among the three types the largest amount of pyroxenes with or without a hornblende mantle. The results of fourty modal analyses and seven chemical analyses are given in Tables 1 and 2, respectively. Petrochemically, the Sasamori type is lower in K2O and higher in SiO2 than the Orikabe type, corresponding with the evidence that the Qz/Kf ratio of the former is higher than the latter (Figs. 2, 4 and 7). Comparing with the other granitic bodies in the Kitakami mountainland the Orikabe granitic body is petrographically similar to the Tabashine granitic body.
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  • Geologic considerations on some natural gas fields, in Niigata Prefecture, Japan
    Characteristics of gas and formation water
    Susumu Nishijima
    1971 Volume 65 Issue 4 Pages 162-179
    Published: April 05, 1971
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.65.162
    JOURNAL FREE ACCESS
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    The characteristics of natural gas have a close relation with formations, that is, the characteristics are nearly the same in one formation, and change comparatively rapidily near the formation boundary.
    If the characteristics of gas are determined in the later stage, by a so called “maturation process” as it is often considered, it might be expected that the characteristics of gas have relation to depth, which in turn controls temperatures and pressures. But the characteristics don't have relation to depth primarily.
    The fact that the characteristics of gas have relation to formations means that gases generated in each formation have individual properties respectively and don't migrate across formation boundaries and don't mix with gases generated in other formations.
    From these facts, the following two cases can be presumed:
    Case (1): In comparatively early stage after sedimentation, the genesis, migration and accumulation of natural gas virtually ended.
    Case (2): On the contrary, in the much later stage after sedimentation, natural gas generates and cannot migrate far because of compaction of sediments.
    Observing modes of existence of gas pools, the writer presumes early migration and therefore takes case (1) above mentioned.
    The characteristics of formation water and interstitial water of mudstone cores also have relation to formations.
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  • [title in Japanese]
    1971 Volume 65 Issue 4 Pages 180-205
    Published: 1971
    Released on J-STAGE: July 13, 2012
    DOIhttps://doi.org/10.2465/ganko1941.65.180
    JOURNAL FREE ACCESS
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