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 71, Issue 8
Displaying 1-4 of 4 articles from this issue
  • Hiroyoshi Yokomizo, Zenzo Moriyama
    1976 Volume 71 Issue 8 Pages 221-228
    Published: August 05, 1976
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
    Two magnesian clay minerals were found in clay veins in the country rocks of the ore deposits of the Kiura mine, Oita Prefecture. A pale pink-coloured material (sample A) is identified as a usual stevensite from its properties. The X-ray pattern of a blackish brown coloured clay (sample B) is obscure, but changes of the pattern after various treatments indicate the mineral to be a random interstratification of an expandable layer and a nonexpandable layer. Its DTA and Infra-red data are very similar to those of the sample A. Therefore, these two clay minerals are concluded as stevensites, of which the crystallinities are different mutually. Their modes of occurrence suggest that these clay minerals are hypogene in origin and formed from a hydrothermal solution charged with magnesium and silica.
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  • MICHIO TAGIRI, HITOSHI ONUKI
    1976 Volume 71 Issue 8 Pages 229-237
    Published: August 05, 1976
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
    The chemical compositions of subcalcic hornblendes, epidotes, white mics and bulk rocks were reported from the Yamagami epiclote amphibolites. The compositional variation of subcalcic hornblende solid solution was discussed in the system of tschermakite-pargasite-eckermanite-glaucophane under the conditions of glaucophanitic metamorphism. The solvus between subcalcic hornblende and, alkali amphibole is wide and subcalcic hornblende is soluble to about 1 in the M4 site alkali content. There are two variation trends of subcalcic hornblendes in glaucophanitic metamorphism. Trend A, that is, the alkali content of the M4 site increases with rising temperature, is the same as the contributions by Black (1973) and Toriumi (1975). Trend B, in which the alkali content, of the M4 site decreases and that of the vacant site slightly increases with rising temperature, is compatible with the general trend of subcalcic to calcic hornblende variation. Trend A is produced by the reactions among albite, chlorite, epidote and quartz, but Trend B must be created by the reactions among iron ores, carbonates, albite and epidote or by the breakdown of subcalcic hornblendeC to clinopyroxene-garnet-subcalcic hornblendeD or to quartz-subcalcic hornblendeD. The change of the trend from A to B is due to not only the metamorphic grade but also the bulk composition, specially the scarcity of the modal content of chlorite, quartz and albite.
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  • SHIGERU SUZUKI, HIROTSUGU NISHIDO, RYOHEI OTSUKA
    1976 Volume 71 Issue 8 Pages 238-247
    Published: August 05, 1976
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
  • KICHIRO KOTO, NOBUO MORIMOTO, HAJIME NARITA
    1976 Volume 71 Issue 8 Pages 248-254
    Published: August 05, 1976
    Released on J-STAGE: August 07, 2008
    JOURNAL FREE ACCESS
    The crystallographic relationships of pyroxenes and pyroxenoids are described based on the new unit cells of Narita (1973). The new unit cells clearly indicate that the pyroxenoids make a homologous series which is composed of the slabs of the pyroxenetype and wollastonite-type structures.
    Ideal structures of the pyroxenoids are constructed from those of pyroxene and wollastonite assuming that large cations occupy the octahedral sites of oxygen atoms. The characteristic deviation from the ideal structure is the expansion of the c axis parallel to the silicate chain of wollastonite. In the structure of pyroxenoids a dense zone which makes an important role in transition is controlled by that of the wollastonite-type structure.
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