Online ISSN : 2186-490X
Print ISSN : 1346-4272
ISSN-L : 1346-4272
Volume 56 , Issue 1-2
Bulletin of the Geological Survey of Japan
Showing 1-6 articles out of 6 articles from the selected issue
  • Shunso Ishihara, Shin-ichi Yoshikura, Shigeo Horikawa, Masatsugu Ogasa ...
    2005 Volume 56 Issue 1-2 Pages 1-8
    Published: April 28, 2005
    Released: November 20, 2014
    Two different granites in their oxygen fugacity during the formation, are seen in the drill cores from the northwestern part of Okayama City. One is coarse-grained granite having no or little rock-forming magnetite, while the other is fine-grained aplitic granite occurring in sheet-like form and containing coarse-grained magnetite in miarolitic aggregates of K-feldspar and quartz. The major and trace elements chemistry indicates that the aplitic granite is crystallized from fractionated melts of the coarse-grained granitic magma. It is suggested that the fractionated magma became rich in H2O which dissociated into O2 and H2 and the hydrogen diffused out to the roof rocks; then the oxygen fugacity was increased to form magnetite. Löllingite was discovered along cracks of the coarse-grained granite at one quarry, reflecting a low sulfur fugacity of the post-magmatic hydrothermal activity of these granites.
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  • Shigeru Terashima, Noboru Imai, Atsuyuki Ohta, Takashi Okai, Masumi Mi ...
    2005 Volume 56 Issue 1-2 Pages 9-23
    Published: April 28, 2005
    Released: November 20, 2014
    A total of 247 soils collected from the southern to northeastern Kanto district were analyzed for selenium (Se) by continuous hydride generation and atomic absorption spectrometry. The average Se content of volcanic ash soils (0.65 ppm, n=176), brown forest soils (0.47 ppm, n=31) and alluvial soils (0.54 ppm, n=40) are more than ten times higher than that of the average igneous rocks. In the case of volcanic ash soils and brown forest soils, the Se is generally enriched in the upper soil layers than in the deeper ones, and positively correlates with organic carbon and sulfur. This may be mainly caused by the biological accumulation process. The Se rich volcanic ash soils are accumulated during the last 15,000 years, reflecting the global warming and the high biological productivity. Several sand layers derived from basement rocks are found in the cores of alluvial soils. Compared to the mud layers, sand layers are poor in Se, organic carbon and most of the heavy metals. The alluvial soils existed under the effects of saline water in the past tense are significantly dominant in sulfur, but not enriched in Se. This may reflect that Se (VI) does not precipitate with hydrogen sulfide. It has been concluded that the geochemical behavior of Se in soil layers is controlled mainly by the mode of occurrence, biological productivity, redox conditions of environments, and migration during diagenesis.
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Notes and Comments
  • (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XCVIII)
    Tatsuro Matsumoto, Seiichi Toshimitsu
    2005 Volume 56 Issue 1-2 Pages 31-36
    Published: April 28, 2005
    Released: November 20, 2014
    In addition to Mantelliceras japonicum Matsumoto, Muramoto and Takahashi and M.cantianum Spath, previously reported from the lower Cenomanian in the Ikushunbetsu Valley of the Mikasa district, M. cf. mantelli (J. Sowerby) from the basal part of the Cenomanian, M. cf. picteti Hyatt and M. cf. dixoni Spath from somewhat higher stratigraphic levels in the same area are described. Also M. cf. couloni (Orbigny) from the Hobetsu district is redescribed with some amendment.
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  • Nobuharu Hori
    2005 Volume 56 Issue 1-2 Pages 37-83
    Published: April 28, 2005
    Released: November 20, 2014
    Paleozoic and Mesozoic radiolarians were recovered from the Jurassic accretionary complex of the Chichibu Belt in the Iragomisaki district, Atsumi Peninsula, Aichi Prefecture, Southwest Japan. Permian and Triassic radiolarians were detected from 7 and 23 samples of chert, respectively. Jurassic radiolarians were obtained from 10, 6 and 11 samples of chert, siliceous mudstone and mudstone, respectively. 108 species belonging to 54 genera are identified, and are shown in plates with undescribed morphotypes as a database for further study. Based on Permian, Triassic and Jurassic radiolarian biostratigraphic schemes, the geologic ages of the examined chert, siliceous mudstone and mudstone samples range from Middle Permian to late Middle Jurassic, early Middle Jurassic to middle Middle Jurassic and early Middle Jurassic to late Middle Jurassic, respectively.
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Abstract of Meeting