巻号一覧
82 巻, 7 号
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氏家 治1987 年 82 巻 7 号 p. 245-256
発行日: 1987/07/05
公開日: 2008/08/07
ジャーナル フリー液相濃集元素のうちLILE (Rb, Sr, K)はマントル交代作用で移動しやすく, Nb, ZrおよびＹは移動しにくい。故に玄武岩の組成をNb/Y-Zr/Y図とLILE/Y-Zr/Y図上で検討すれば,マントルの特徴を知り得る。東北日本弧および利尻火山下のマントルは本来, N型中央海嶺玄武岩の根源物質に類似する。ただし東北日本弧と利尻火山下のマントルは,かっての火成作用のために後者よりも液相濃集元素に乏しくなっている。東北日本弧の玄武岩マグマは,マントルが交代作用を受けてLILEに富化した後に生じる。交代作用の結果として海溝側(那須火山帯)の玄武岩は相対的にSrに富み,背弧側(鳥海火山帯)のそれはRbとKに富む。利尻島下のマントルは交代作用を殆んど受けていない。
島名の英和対照Dog,独島(又は竹島); Jeiu,済州島; Oki-Dozen,隠岐島前; Oshima-oshima,渡島大島; Rishiri,利尻島; Ulreung, 鬱陵島。抄録全体を表示PDF形式でダウンロード (541K) -
岡本 健二, 木下 修, 野中 健二, 八木 伸二郎1987 年 82 巻 7 号 p. 257-268
発行日: 1987/07/05
公開日: 2008/08/07
ジャーナル フリーThe Miocene granitic rocks in the southern Kyushu were analyzed by the INAA and gammaray counting for 17 trace elements, and by wet chemistry for major elements. Based on unusual differentiation trends of Na2O and Th/U, the Th/U-K2O/Na2O diagram is proposed as a clue to study of the mixing process between two differently originated magmas. Present results show that all the differentiation trends direct towards a fixed point on that diagram, the Th/U and K2O/Na2O ratios of which are 6.5 and 1.7 respectively. This unfamiliar converging differentiation trend is concluded to indicate the mixing of two magmas, one of which has the composition of the fixed point. The point is explained to represent the minimum melt by partial melting in the Qtz-Or-Ab-An-H2O system, based on comparison of its K2O/Na2O ratio with that of the Sierra Nevada batholith and melting experiments. The similarity of Th/U ratio between the fixed point and shales or sandstones of the Shimanto belt suggests that they have been source materials to be partly melted. The differentiation trends of the other elements are also explained by the mixingmodel.抄録全体を表示PDF形式でダウンロード (833K) -
関 陽太郎, 平野 富雄, 渡辺 邦夫1987 年 82 巻 7 号 p. 269-279
発行日: 1987/07/05
公開日: 2008/08/07
ジャーナル フリーRock-cliff Budda sculptures of Odaka Town, Fukushima Prefecture, Japan were carved about one thousand years ago on the Neogene dacitic tuffaceous sedimentary rocks.
These sculptures have been badly decayed by (1) the formation of scabs composed chiefly of gypsum, epsomite and thenardite with subordinate amounts of kogarkoite, langbeinite, zoherite, hydroglauberite, starkeyite, jurbanite, loeweite, hexahydrite, alunogen, mirabilite, glauberite, syngenite, hemihydrite and sylvite at the surface of the sculptures by the evaporation of groundwater percolated through the voids and joints in the Neogene volcanogenic sedimentary rocks and (2) the exfoliation of the these scabs and near-surface part of Neogene sedimentary rocks, particularly due to the heaving during the freezing-thawing cycle of seeped groundwater in winter season.抄録全体を表示PDF形式でダウンロード (5452K)
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