岩石鉱物科学
Online ISSN : 1349-7979
Print ISSN : 1345-630X
43 巻 , 6 号
November
選択された号の論文の8件中1~8を表示しています
会長挨拶
原著論文
  • 孫 羽, 廣井 美邦, 大和田 正明
    2014 年 43 巻 6 号 p. 203-214
    発行日: 2014年
    公開日: 2014/12/29
    [早期公開] 公開日: 2014/12/06
    ジャーナル フリー
      The Cape Hinode area in East Antarctica exposes Mid-Proterozoic tonalites, which are similar in chemical composition to high-SiO2 adakites and Archean tonalite-trondhjemite-granodiorite. They contain enclaves of ultrabasic-intermediate and calc-silicate metamorphic rocks of various dimensions, as well as xenocrystic garnet and kyanite. Pinite and carbonate minerals surrounding kyanite inclusions in plagioclase are alteration products after coronas of anorthite and spinel with or without corundum, alkali feldspar, rutile and magnetite. Further observations reveal that thin tonalitic veins cutting calc-silicate enclaves carry kyanite fringed by similar anorthite coronas. Such kyanite sometimes encloses quartz inclusions. The thin tonalitic veins are characterized by the occurrence of dark green clinopyroxene as the main mafic mineral, low aluminum saturation index (0.75) in spite of the occurrence of kyanite, and a non-adakitic geochemistry.
      The calc-silicate enclaves in tonalites are composed mainly of calcic plagioclase, Ca-garnet and/or clinopyroxene. The symplectitic intergrowth of anorthite and Ca-garnet is chemically close to epidote, and may be produced by successive melt-involving and epidote-consuming reactions. These chemical and textural features of kyanite and other minerals occurring in and around kyanite, thin tonalitic veins, calc-silicate enclaves, and tonalites indicate the significance of metamorphic and magmatic epidotes during partial melting of eclogites of young and hot slab origin.
特集号「日本の花崗岩とテクトニクス」その3
原著論文
  • 谷岡 裕大, 若杉 勇輝, 壷井 基裕
    2014 年 43 巻 6 号 p. 215-217
    発行日: 2014年
    公開日: 2014/12/29
    ジャーナル フリー
      The Tadamigawa granitic rocks are located at southwestern part of Fukushima prefecture, northeastern Japan. The granite intrudes into Jurassic sedimentary complex of the Ashio terrane. The granites around the Hinoemata village area are divided into two rock types: the Tadamigawa granite and the Hinoematagawa granite. On the field occurrence, the Tadamigawa granite intrudes into the Hinoematagawa granite. In this study, 7 samples of the Hinoematagawa granite and 32 samples of the Tadamigawa granite were analyzed for major, minor and REE compositions by XRF and ICP-MS, respectively. Moreover, we obtained K-Ar biotite ages from both granites, and iron oxidation ratios by titrimetry with potassium permanganate. SiO2 contents of the Hinoematagawa granite and the Tadamigawa granite range from 59.6 to 69.4 wt% and from 62.5 to 76.1 wt%, respectively. K-Ar biotite ages of the Hinoematagawa granite and the Tadamigawa granite at Taishaku Mountains are 102.3 ± 2.2 Ma and 102.7 ± 2.2 Ma, respectively. However, the Tadamigawa granite at Inagawa area and Tadamigawa area show the ages of 61.7 ± 1.4 Ma and 89.6 ± 1.9 Ma, respectively. The granites are characterized by LREE enrichment, and have relatively constant patterns normalized by CI chondrite. The Hinoematagawa granite shows small negative Eu anomaly (Eu/Eu* = 0.73-1.01), and the Tadamigawa granite show large Eu anomaly (Eu/Eu* = 0.26-0.89). The value of Eu anomaly increases with decreasing anorthite content and the Eu anomaly might be concerned with the differentiation of anorthite. The Hinoematagawa granite and the Tadamigawa granite may be generated from the same magma origin. The Hinoematagawa granite shows low Fe2O3/FeO ratio (0.28-0.39), however, the Tadamigawa granite shows high Fe2O3/FeO ratio (0.24-1.45). The Hinoematagawa granite may be generated from the magma which has low oxygen fugacity. The difference between both granites is concerned with oxygen fugacity variation of source magma.
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ニュース
学会記事
  • 2014 年 43 巻 6 号 p. 229-246
    発行日: 2014年
    公開日: 2014/12/29
    ジャーナル 認証あり
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