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 47, Issue 5
Displaying 1-4 of 4 articles from this issue
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  • Mineralogical studies on the chromites in the Tari District, Tottori Prefecture
    Jun-ichi Kitahara
    1962 Volume 47 Issue 5 Pages 167-174
    Published: May 05, 1962
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.47.167
    JOURNAL FREE ACCESS
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    The chromite deposits in the Tari district are the differentiation products of the ultrabasic magma and lenticular or massive in form. They extend nearly parallel to the longer axis of serpentinite body. Generally a massive ore predominates in the inner part of the deposit and a porphyritic ore in the outer part. The ore is now working at the Ogiri and the 34-m levels of hirose mine and No. 7, Minami, and Chugri levels of Wakamatsu mine. The Cr2O3 content of 47 samples of the ore is low, ranging from 31.22 to 41.33%.
    It is ascertained that the inner part of ore body is highest in spinel composition and the lowest in magnetite composition, that the edge is high in spinel compostion and low in magnetite composition, and that the marginal part is low in spinel composition and high in magnetite composition.
    According to the triangular diagram represnting norm, the chromite mineral belongs to chromian spinel, which is rare in Japan as well as in foreign countries.
    In thin section, chromites from the inner and the edge parts are mostly yellow to orange in color, while the outer part is usually black. The indices of refraction of the chromites are n=1.86-1.89 and color of the chromite in thin section is yellow through light red to red with increase of the index. The lattice constants ranging from 8.188 to 8.244À, become larger with increase in the quantity of Cr2O3 and FeO+Fe2O3.
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  • Studies on the facies variation of gabbro surrounding pyrrhotite deposits (II)
    Choru Kim
    1962 Volume 47 Issue 5 Pages 175-187
    Published: May 05, 1962
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.47.175
    JOURNAL FREE ACCESS
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    In this paper, the writer presents some regular variations of habit and grain size of plagioclase that constitutes wall rock gabbro as an altered factes of surrounding nickeliferous pyrrhotite deposits. The variations are closely allied to the variations of composition which have already been reported in former papers.
    The tendencies of variations are pursued by the statistical measurements of plagioclase habit that is represented in the growth length of (011)/(001), and grainsize stretching to (010) and (001).
    It is concluded that the altered factes of nickeliferous pyrrhotite deposits is represented by the plagioclase habit of (010)/(001)=1.5_??_2.0 and composition of An (60-63). Several gabbroic factes of country rocks which are metasomatically altered from olivine gabbro and no rite, have unique value in composition, habit and grain size as shown in Figures 1_??_5. Their courses of development were closely agreed with the mineralization of nickeliferous pyrrhotite deposits.
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  • Sassolite from Iwo-zima Island. Kagoshima Prefecture
    Takeo Okano
    1962 Volume 47 Issue 5 Pages 188-191
    Published: May 05, 1962
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.47.188
    JOURNAL FREE ACCESS
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    Sassolite has been recently found for the first time in. Japan at Iwo-dake Volcano, Iwo-zima. Near the explosio crater of Iwo-dake there are many fumaroles, from which large amount of volcanicgas is issued. Sassolite was found as one of the sublimate minerals atsome fumaroles, where the temperature was about 200°C. Sassolite formspseudohexaaonal plates, less than 0.5mm. in diameter, and has the following properties; sp, gr.(28°C)=1.478, α=1, 331, β=1.448, γ=1.453, 2Vx=about 5°. Chemical composition is B2O3 56.39 and H2O 43.61. The strongest1ines of X-ray powder pattern of the mineral are 3.16À (100), 5.98À (15), 5.86À (10), and 1.58À (5).
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  • PETROGRAPHY AND PETROCHEMISTRY OF THE ROCKS FROM IWATE VOLCANO, NORTHEASTERN JAPAN
    KOSUKE ONUMA
    1962 Volume 47 Issue 5 Pages 192-204
    Published: May 05, 1962
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.47.192
    JOURNAL FREE ACCESS
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    Iwate Volcano is a composite stratovolcano consisting of two tripple cones, older and younger volcanoes, and belongs to the northern sub-zone of the Nasu volcanic zone. The calderas, which are found in this volcano, represent two types of caldera belonging to Glencoe type. All of the lavas and pyroclastics of this volcano belong to tholeiitic rock series, but rocks of calc-alkali rock series are never found. The rocks of the older volcano are generally more advance in the stage of differentiation than those of the younger volcano, which are little differentiated. The chemical compositions of these rocks are also described.
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