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 50, Issue 3
Displaying 1-4 of 4 articles from this issue
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  • Petrological studies on the metasomatic syenites in Japan. Part 1. Syenites of the Cape of Ashizuri, Kôchi Prefecture
    Nobuhide Murakami, Hiroshi Matsuo
    1963 Volume 50 Issue 3 Pages 93-109
    Published: September 05, 1963
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.50.93
    JOURNAL FREE ACCESS
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    The syenites of the Cape of Ashizuri are fine to coarse-grained, and composed mainly of albite to oligoclase, highly sodic orthoclase, ferropargasitic amphibole, and green biotite. They are transitional to the older biotite granite and intruded by the younger biotite granite. From field evidences and petrographic characters, it is considered that the syenites have been derived from the older granites by the metasomatic action of alkali solution, originated probably from the younger granite magma. The addition of Al2O3, Fe2O3+FeO, CaO and Na2O to the original rock is accompanied by the subtraction of SiO2 and K2O, slight increase in oxidation ratio, and high decrease in Or content in potash feldspars. The syenites of the Cape of Ashizuri are considered to have been formed at comparatively higher temperature and lower oxygen pressure than some syenitic rocks in southwestern Japan.
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  • Common hornblendes in metagabbro and amphibolites of Takozu district, Kitakami Mountainland
    Mitsuo Shimazu
    1963 Volume 50 Issue 3 Pages 110-117
    Published: September 05, 1963
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.50.110
    JOURNAL FREE ACCESS
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    The ultramafic masses in this district intrude into the green rocks of the Motai formation and the slate of the Tobigamori formation. The green rocks of the Motai formation are partly composed of the glaucophane rocks.
    Three common hornblendes were separated from the metagabbro and amphibolites, which associate with the serpentain masses, and analysed chemically. The chemical analyses and the atomic ratios are shown in Table 1. The results plotted on the Hallimond's triangle diagram indicates that the hornblendes of the Takozu district are similar in composition to that of the Miyamori and Abukuma districts.
    Optical and X-ray powder data are shown in Table 2 and 3. The observed mineral parageneses of these rocks are
    Common hornblende-albite-epidote-biotite-sphene
    Common hornblende-oligoclase-epidote-chlorite-sphene
    Lastly, petrogenesis of metagabbro and amphibolite is briefly discussed from the views of mineral paragenesis and mineralogical properties of the hornblendes.
    It may be that these rocks were retrogressively formed from gabbroic rocks in the condition of epidote amphibolite and amphibolite facies.
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  • Minor elements in pyrite and their effects on the cube-edge of pyrite
    Kiyoshi Takimoto, Taneo Minato, Shuichiro Hirono
    1963 Volume 50 Issue 3 Pages 118-131
    Published: September 05, 1963
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.50.118
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    Investigations concerning the concentration of minor elements (Co, Ni, Mn, As) in pyrites and cube-edge measurements were carried out on thirty-nine specimens taken from the Chichibu mine (26 samples), the Taishu mine (7 samples), and the Ashio mine (6 samples), by using X-ray fluorescent method as well as X-ray diffraction method. The results obtained are as follows;
    (1) Pyrites in the Chichibu mine and the Taishu mine show considerably higher in Co and Ni contents, and also in the Co: Ni ratio than in the Ashio mine. As to the contents of both Mn and As in pyrites, the results show only slight differences among three mines.
    (2) Generally speaking, the Co and Ni contents and the Co: Niratios in pyrites correlate negatively with the As contents, but correlate positively with Co and Mn contents.
    (3) While As contents of pyrites decreases with depth at the mines, the Co content and the Co: Ni ratio increase; no significant trends with depth arc observed in Ni and Mn contents.
    (4) The result of the present study indicates that pyrites from high-temperature deposits show generally high Co content and high Co: Ni ratio, and inversely low As content.
    (5) The cube-edges of pyrites measured range from 5.41759 to 5.41937 A. It seems probable that the values increase with the increase of the amounts of both Co and As components in pyrites. The equation pertaining to the cubeedge of pyrite can be written as
    Z=5.41752+0.0634X+0.0025Y,
    where Z(A) is an unit cell size, X and Y are weight percentages of Co and As components, respectively.
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  • Chemical composition and optical properties of sanidine from Taiji, Wakayama Prefecture
    Ken-ichiro Aoki
    1963 Volume 50 Issue 3 Pages 132-133
    Published: September 05, 1963
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.50.132
    JOURNAL FREE ACCESS
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