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 68, Issue 8
Displaying 1-3 of 3 articles from this issue
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  • ELECTRON-MICROSCOPIC INVESTIGATION OF MICROCLINE-ORTHOCLASE PERTHITE
    Mizuhiko Akizuki
    1973 Volume 68 Issue 8 Pages 237-245
    Published: August 05, 1973
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.68.237
    JOURNAL FREE ACCESS
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    Microscopic structures which are considered to represent a transitional state from orthoclase to microcline were observed in microcline-orthoclase perthite by means of the optical and electron microscopes. Due to the cross-hatching of the orthoclase, strain existing around perthitic albite in the orthoclase is stretched in the direction parallel or perpendicular to the b-axis. This results in the formation of microclinic band structures, which can cross each other because of the cross-hatching in the bands. Further, along one direction of the crosshatchings, albite or pericline twinning of microcline take place with increase of triclinic nature, while other lamellae normal to the twins remain in its original state. Orientation of the local stress around the perthitic albite in orthoclase determines the final product, albite type or pericline twinnings. Since the crystal lattice within one individual stress band in orthoclase has the same orientation, the maximum microcline formed by the later recrystallization will have the same orientation. Exsolved albite shows fine albite twinnings under the electron microscope.
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  • CHLORITIC CLAY MINERALS IN TUFFACEOUS SANDSTONE OF THE MIOCENE GREEN TUFF FORMATION, YAMANAKA DISTRICT, ISHIKAWA PREFECTURE, JAPAN
    KEIJI KIMBARA, TOSHIO SUDO
    1973 Volume 68 Issue 8 Pages 246-258
    Published: August 05, 1973
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.68.246
    JOURNAL FREE ACCESS
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    Chloritic clay minerals occur widely in the Miocene tuffaceous sandstone, associated with laumontite, prehnite and epidote. The chloritic minerals are divided into four zones on the basis of the mineral assemblages as follows; Corrensite Zone, Transitional Zone, Swelling chlorite Zone and Chlorite Zone.
    Mineralogical properties of interstratified chlorite-saponite (corrensite) do not vary with horizon. Chlorite was formed from the interstratified mineral through swelling chlorite by hydrothermal alteration. Mineralogical and petrological data of these chloritic clay minerals are given in this paper.
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  • COEXISTING OLIVINE AND PYROXENES FROM THE ACOJE ULTRAMAFICS, PHILIPPINES
    TERUYUKI TAKEDA, HITOSHI ONUKI
    1973 Volume 68 Issue 8 Pages 259-267
    Published: August 05, 1973
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.68.259
    JOURNAL FREE ACCESS
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    Three selected peridotites, their olivines and pyroxenes from the Acoje mine, Philippines were chemically studied. From the data based on the pyroxene grid the Acoje peridotites seem to be recrystallized under conditions prevailing in the plagioclase peridotite field, and this estimation is not inconsistent with the suggestions from the distribution coefficient data of Fe+2-Mg between the coexisting silicates in the peridotites.
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