The Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists
Online ISSN : 1883-0765
Print ISSN : 0021-4825
ISSN-L : 0021-4825
Volume 52, Issue 5
Displaying 1-3 of 3 articles from this issue
  • Yukio Matsumoto, Michitoshi Miyahisa, Kiyoshi Ishibashi, Hitoshi Yamau ...
    1964 Volume 52 Issue 5 Pages 147-163
    Published: November 05, 1964
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
    Results of the geological and petrological study of the volcanic rocks in Takahama, Matsuyama City and its surrounding area are summarized as follows :
    1 Upper part in the Gogoshima group is consisted mainly of the “Matsuyama welded tuff”, so named by the writers.
    2 The welded tuff is a pumice flow, and its degree of welding is high. Moreover, it has all the appearence of pichstone.
    3 Essential constituent minerals of the welded tuff are biotite, augite, hypersthene, plagioclase, sanidine and abundant glass. Furthermore, pieces of pumice and accedental matirial are present. The matrix showing vitroclastic texture is composed largerly of glass.
    4 Their chemical and normative mineral compositions are shown in table 2. As seen from the table, they are generally rich in K2O, P2O5 and H2O+ contents, while poor in Na2O, CaO and total FeO. Petrochemically, its welded tuff is potash-rhyolite.
    5 This formation is possibly of the late Miocene age, and may be correlated to the Ishizuchi group in Shikoku. Namely, as an example of the volcanic activities of the Setouchi series in the Miocene-Pliocene (G-H stage), say, the Matsuyama welded tuff are conceivable.
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  • Basalts of Kibi-plateau
    Kyoko Oji, Yoshio Oli
    1964 Volume 52 Issue 5 Pages 164-173
    Published: November 05, 1964
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
    Basalts of Kibi plateau are exposed as many domes of small scale and a few lava flows as well which were erupted in Pleistocene age. They all belong to the alkali rock series and are classified into olivine or titanaugite olivine trachybasalt, titanaugite olivine trachydolerite and titanaugite olivine trachyandesite. Eleven of them are chemically analysed. The distinct characteristics of the rocks of this province are as follows : 1) They are chemically richer in MgO and poorer in Al2O3 because of the abundance of olivines, titanaugites and xenocrystic clinopyroxenes. 2) Some have properties which closely resemble those of limburgite in both mineral and chemical constituents. 3) Olivine and pyroxene rich inclusions are contained in the rocks of this province, and especially in Arato-yama and Yunodan-yama are found the largest occurrence of the inclusions in Chugoku area. 4) Zeolite like mineral occurs frequently in the marginal part of the inclusions.
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  • Takashi Yamamoto, Kazuko Matsukuma
    1964 Volume 52 Issue 5 Pages 174-186
    Published: November 05, 1964
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
    Lately we have ascertained the characteristic features of zircon in igneous rocks. In that case we have also pointed out that the zircons of probable sedimentary origin were encountered in igneous rocks. In this paper, the writers attempted to reveal the mineralogical features of zircon in sedimentary rocks, mostly sandstones of Tertiary age from Northern Kyushu and Hokkaido districts. Many varieties of zircon with such color as pale orange, pale blue, brown, purple and colorless are observed in these sedimentary rocks. These zircons are usually 0.15×0.06mm in size and have prominent ‘c-type’ crystal phase. And it should be emphasized that these sedimentary zircons presented characteristically rounded ‘R’ form. Distinction between sedimentary zircon and igneous zircon would be clear from the fact that zircons of rounded form ‘R’ amounted to more than 20 to 50 per cent in the sedimentary rocks in contrast with less than 20 per cent in igneous rocks.
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