Chikyukagaku
Online ISSN : 2188-5923
Print ISSN : 0386-4073
ISSN-L : 0386-4073
Volume 14, Issue 2
Displaying 1-5 of 5 articles from this issue
Special Contribution
Original Papers
  • Yoshihiro UJIIE
    1981 Volume 14 Issue 2 Pages 62-68
    Published: March 30, 1981
    Released on J-STAGE: November 17, 2016
    JOURNAL FREE ACCESS
    Organic maturation of kerogen was discussed from the yielded n-alkanes and weight losses by the pyrolysis of 67 kerogens separated from the Upper Cretaceous to Miocene muddy rocks in the northern part of Hokkaido. The results are as follows; 1) Ratios of n-C4H10/CH4 and n-C6H14/CH4 of the pyrolyzed products increase with burial depth in the Miocene core samples of the MITI-Hamayuchi Borehole, but decrease in the Paleogene and Cretaceous core samples of the MITI-Sorachi Borehole. 2) n-Alkane composition generated from kerogens by pyrolysis at 200℃ depend on their geologic ages, though independent at 400℃. Ratios of C16〜C20/C10〜C15 generated at the former condition decrease from the Neogene kerogens to the Cretaceous through the Paleogene. 3) There is the distinct correlation of the Carbon Preference Index of n-alkanes (C13〜C20) between the pyrolyzed products of each kerogen at 200℃ and 400℃, the former being smaller than the latter, though they do not show any relation with burial depth.
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  • Nobuki TAKAMATSU, Kyoko SHIMODAIRA, Masayuki IMAHASHI, Ryuma YOSHIOKA
    1981 Volume 14 Issue 2 Pages 69-76
    Published: March 30, 1981
    Released on J-STAGE: November 17, 2016
    JOURNAL FREE ACCESS
    Powdered granitic rocks were allowed to react with distilled water under various conditions to estimate the formation mechanism of natural waters from granitic area and to discuss on the factors influencing the chemical composition of the waters. The experimental results indicate that the chemical composition and pH of the waters are influenced by the kind of granitic rocks, the water/rock ratio and PCO2. The alkaline ground waters may result from the reactions of granitic rocks with the waters having low PCO2. The ground waters from granitic areas where CO2 from underground occurs abundantly are neutral or weak acidic, and their major species are Na+, Ca2+, HCO3-. The proportion of the components is nearly equal to that of the surface waters. The percolation time of ground waters in granitic areas was inferred to be relatively short because of the high permeability of water into granitic rocks and low content of dissolved species. Accordingly, the metastable alminosilicates produced during the incongruent dissolution of granitic rocks, may control the chemical composition and pH of the ground waters.
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  • Yoshiaki IKEHARA, Kazuo TAGUCHI, Akio HIRAI, Yoshikazu SEKIGUCHI
    1981 Volume 14 Issue 2 Pages 77-87
    Published: March 30, 1981
    Released on J-STAGE: November 17, 2016
    JOURNAL FREE ACCESS
    The relationship between the reflectance value of vitrinite in kerogen and "principal zone of oil formation" in the Neogene Tertiary of northeastern Japan was examined. The reflectance value of about 0.5% was obtained as the value corresponding to the upper limit of principal zone of oil formation. In addition, the vitrinite reflectances of the samples from the marginal regions of sedimentary basin were measured to compare with those of oil producing areas in the central part of the basin. As the results, the reflectance values from the marginal parts were distinctly lower than those of the equivalents in the central part of the basin and did not show any remarkable increase toward the lower formations.
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  • Noriyuki SUZUKI, Kazuo TAGUCHI
    1981 Volume 14 Issue 2 Pages 88-98
    Published: March 30, 1981
    Released on J-STAGE: November 17, 2016
    JOURNAL FREE ACCESS
    Eight kerogen fractions obtained by the size-fractionation of the siltstone from the Haizume Formation of Pliocene age were examined by elemental analysis, and infrared and electron spin resonance (ESR) spectrometry. The kerogens from coarse fractions were relatively rich in aromatic structure, and they indicated characteristics smilar to fusinite maceral of coal, showing low g-value (2.0029), narrow line width (2.62G) and high spin density in the ESR properties. On the other hand, the kerogens from fine fractions were rich in functional groups and aliphatic structure, composing of amorphous kerogen and they showed similar patterns to humic acid from marine muds in the ESR spectrum. Kerogens associated with clay-size fractions obtained from thirteen core samples of UMEDA R-1, were investigated from the viewpoint of diagenetic change. As the results, a systematic change of those kerogen properties with burial was recognized, particularly in the ESR properties though the treated samples were immature in the degree of organic alteration. It is noteworthy that the variation of ESR line width from gradual increase to rapid decrease in the early stage of diagenesis was recognized in this study. This will be attributed to that clay-size fraction kerogens are composed of predominant ones in functional groups and aliphatic structure. Consequently, This may be regarded as being one of the special features in the diagenesis of kerogens associated with clay-size fraction.
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