日高帯のマントル物質の形成とマグマ活動, 北海道, 幌満カンラン岩体に発達する流れ褶曲 Magmatism and Genesis of Mantle Materials of Hidaka Belt, Flow fold of the Horoman peridotite complex, Hokkaido, Japan

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幌満カンラン岩体のスピネル・レーゾライトに発達する横臥褶曲の形態および変形組織を解析した。この褶曲軸面は綿状構造がつくるフォリエーションにほぼ平行で閉じた流れ褶曲である。褶曲組織を構成するカンラン石の格子ファブリックをみると, Z軸が褶曲軸面上で褶曲軸に斜交したパターンを示し, X軸は褶曲軸面に高角で斜交するパターンを示す。このファブッリックは圧縮場で形成される褶曲構造形成の応力配置に整合する。この他に, Z軸がリニエーションに調和するファブリックパターンがあり, これはいわゆるアルプス型のテクトナイトの特徴である。横臥褶曲はアルプス型のテクトナイト形成前でマントル・ダイアピル過程で形成されたと推定される。

Recumbented fold was found in spinel lherzolite from the Lower Zone of the Horoman peridotite complex, Hidaka belt, Hokkaido, northern Japan. The folds are usually tight and flow fold type. Their axial planes are parallel or subparallel to a foliafion and the fold axes are subparallel to a mineral lineation. Lattice preferred orientation of olivine in the texture of the fold structure is characterized by lie on the great circle of Z-axis parallel/slightly oblique to the axial plane. X-axes maxima are concentrated in a direction perpendeular to the fold axial plane/foliation. On the other hand, lattice orientation of olivine in the texture of non-fold structure shows that the concentration of Z-axes are parallel to the mineral lineation and X-axes maxima perpendicular to the foliation plane. The former lattice fabric is consistent to the stress field of the folding under a compression and the later fabric shows the fabric of an "Alpine-type" with Z-axes parallel to the mineral lineation. Lattice orientation of olivine in the porphyroclastic texture tends to diffuse. Dislocation substructure is observed in coarse and fine grained olivine which consititutes the flow-fold using TEM. Straight or slightly curved dislocation, short and tangle dislocations, tilt boundary can be observed in the coarse grain. The same substructures, devoid of tilt boundary can also be observed in the fine grains. On the other hand, subgrain wall structure can be observed in the fine grains of which constituted the matrix of the porphyroclastic texture. The deformational mechanism of plastic flow of these grains might be due to the dislocation slip and the glide acted on the former grains, and subgrain rotaion has acted on the latter one under a dynamic recrystallization during formation of the porphyro-clastic texture. Dislocation density in the both coarse and fine grains in the folded and porphyroclastic domains is roughly same degree. The fabric of an "Alpine-type" in the Horoman peridotite might be formed under the solid state during its intrusionin to the crust. The recumbent flow fold in the peridotite might be formed during uplift of a mantle diapir from the upper mantle.

収録刊行物

  • 地質学論集

    地質学論集 47, 209-218, 1997-04-24

    日本地質学会

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各種コード

  • NII論文ID(NAID)
    110003025965
  • NII書誌ID(NCID)
    AN00141779
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    03858545
  • NDL 記事登録ID
    4283364
  • NDL 雑誌分類
    ZM49(科学技術--地球科学--地質)
  • NDL 請求記号
    Z15-322
  • データ提供元
    CJP書誌  CJP引用  NDL  NII-ELS  NDL-Digital 
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