Earth Science (Chikyu Kagaku)
Online ISSN : 2189-7212
Print ISSN : 0366-6611
Volume 64, Issue 5
Displaying 1-4 of 4 articles from this issue
  • Shigeki CHIBA
    Article type: Article
    2010 Volume 64 Issue 5 Pages 179-181
    Published: September 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL OPEN ACCESS
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  • Md Fazle KABIR, Akira TAKASU
    Article type: Article
    2010 Volume 64 Issue 5 Pages 183-192
    Published: September 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL OPEN ACCESS
    The Seba eclogitic basic schists in the Sambagawa metamorphic belt of the Besshi district in central Shikoku, southwest Japan, preserve evidence of two distinct metamorphic events. These are a first eclogitic metamorphic event, and a second glaucophane-barroisitic metamorphic event. The peak metamorphic conditions of the first eclogitic metamorphic event are deduced from the mineral assemblage of schistosity-forming minerals of the eclogite facies (T=610-640℃ and P=12-24kbar; Aoya 2001). The peak eclogitic conditions were followed by a clockwise decompression P-T path, with retrogression into the epidote amphibolite facies at T=400-535℃ and P=6-7kbar. These conditions were obtained from phases replacing the minerals of the peak metamorphic conditions. The second glaucophane-barroisitic metamorphic event is defined by distinctly zoned amphiboles which suggest a prograde path from the epidote-blueschist facies to the epidote amphibolite facies. The prograde path is similar to that of surrounding non-eclogitic Sambagawa schists. The Seba eclogitic basic schists were juxtaposed with non-eclogitic Sambagawa schists during the prograde metamorphism of the non-eclogitic Sambagawa schists. These amalgamated metamorphic sequences subsequently underwent prograde metamorphism reaching the epidote-amphibolite facies, and were then exhumed to shallow crustal levels.
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  • Shohei TOMIYOSHI, Akira TAKASU
    Article type: Article
    2010 Volume 64 Issue 5 Pages 193-200
    Published: September 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL OPEN ACCESS
    The Sambagawa metamorphic belt in the north and the Mikabu greenstone belt in the south extend to the east and the west in the Ise district of eastern Kii Peninsula. Lenticular intercalations of pelitic, siliceous and basic schists occur along the Amabuchi River within the Mikabu greenstone belt. The pelitic schists frequently contain lawsonite. The mineral assemblages of the lawsonite-bearing pelitic schists is quartz+albite+chlorite+phengite+lawsonite±calcite. K-Ar phengite ages of the lawsonite-bearing pelitic schists occurring in the Mikabu greenstone belt and the pelitic schists of the Sambagawa schists are 93-99Ma and 84Ma, respectively. The Sambagawa schists in the northern Ise district and the Mikabu greenstones in the southern Ise district are correlated with Sambagawa schists (77-84Ma) and lawsonite-bearing schists of the Kebara Formation (89-103Ma) distributed in the Shimizu-Misato area, western Kii Peninsula.
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  • Shigeki CHIBA
    Article type: Article
    2010 Volume 64 Issue 5 Pages 201-205
    Published: September 25, 2010
    Released on J-STAGE: May 16, 2017
    JOURNAL OPEN ACCESS
    Kobandai-san was a mountain peak which was a part of Bandai Volcano. It disappeared when the mountain collapsed on July 15, 1888. A writer discovered pictures in which the shapes of the Kobandaisan were drawn before the disappearance. These pictures are illustrations of the "Shinpen Aizufudoki" from Mrs. Otomo Takino. There are two drawing of Kobandaisan in this illustration. These pictures were drawn surrounding Bandai volcano. One drawing is of the northwestern side from the south side of Bandai Volcano. One more drawing is of the north side from the east of Bandai Volcano. Through inspection, it is understood these the shapes of Kobandai-san were drawn before the collapse of 1888 eruption. From these shapes of Kobandai-san, we can infer "The top part of Kobandaisan consisted of three peaks", and " There was a big dale between Kushigamine and Kobandai-san". For this reason, "Shinpen Aizufudoki" kept by Mrs. Otomo Takino are very important materials for the recreation of the form of Kobandai-san.
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