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タイトル: Some Heavy Accessory Minerals in Granitic Rocks from the Tsukuba District, Ibaraki Prefecture.
その他のタイトル: 筑波地方産花崗岩の副成分重鉱物
著者: Ichimura, Takeshi
著者(別言語): 市村, 毅
発行日: 1955年12月10日
出版者: 東京大学地震研究所
掲載誌情報: 東京大學地震研究所彙報. 第33冊第3号, 1955.12.10, pp. 385-395
抄録: (i) Biotite granite or two-mica granite is extensively exposed in the Tsukuba district, where the Upper Paleozoic sediments were intensely metamorphosed by their large intrusive bodies. They are represented by the Tsukuba-type, Inada-type and Kamishiro-type granites which were successively intruded. (ii) Of these, the Tsukuba-type and Inada-type granites were selected to investigate their heavy accessory minerals. These granites were crushed, and heavy accessory minerals were separated by using Thoulet solution. (iii) The heavy accessory minerals thus obtained and examined are zircon, monazite, apatite, garnet, titanite and allanite. The amount of these minerals varies from place to place. (iv) The commonest one is shown by zircon which has different crystal habits and colors even in the same specimen. The zircon taken out from the Tsukuba-type granite is characterized by the abundance of sharp and long prismatic forms. It is colorless and has a very clear appearance. On the contrary, that of the Inada-type granite is mostly represented by stout prismatic crystals which are occasionally rounded. Such difference in crystal form may be of use in clarifying the distinction between these two types of granite. (v) Moreover, it is noteworthy that the same specimens contain colorless and pink zircon crystals together in various proportions. This is a common feature to be seen in the biotite or two-mica granite of the Tsukuba district. In such a case, it is, however, uncertain whether there are zircon crystals derived from Paleozoic sediments subjected to contamination. (vi) Monazite and apatite are also important accessory minerals of granitic rocks exposed in the contact aureole. They are especially concentrated near the contact, where Paleozoic sediments are highly metamorphosed. In such a case, the frequency of apatite seems to increase in proportion to the amount of biotite.
筑波地方に産する2種の花崗岩(稲田型花崗岩と筑波型花崗岩)に含まるる副成分重鉱物の中,ジルコソ,モナヅ石,燐灰石,クサビ石,柘榴石,褐簾石などについて,顕微鏡下の研究を行つた.この結果,ジルコンは,貫入期を異にするこれ等両種の花崗岩を区別するに役立ち,又モナヅ石や燐灰石には,両花崗岩共,秩父系との接触部やそれに近い場所,或はその捕獲岩に富む場合に殊更集中する傾向があることを確めた.然し柘榴石とかクサビ石とか褐簾石には,斯る特徴が認められない.
URI: http://hdl.handle.net/2261/11820
ISSN: 00408972
出現カテゴリ:東京大学地震研究所彙報
東京大学地震研究所彙報

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