韓国中生代花崗岩質岩の Nd, Sr 同位体組成 Nd and Sr Isotopic Signatures of Mesozoic Granitoids in South Korea

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著者

    • 金 奎漢 KIM Kyu Han
    • Department of Science Education, Ewha Womans University Department of Science Education, Ewha Womans University
    • 朴 成淑 PARK Seong Sook
    • Department of Science Education, Ewha Womans University Department of Science Education, Ewha Womans University
    • 羅 椿基 NA Choon Ki
    • Department of Geoscience, University of Tsukuba Department of Geoscience, University of Tsukuba

抄録

韓半島の中生代花崗岩質岩の全岩のεNdは-14.9~+0.4であり,初生<SUP>87</SUP>Sr/<SUP>86</SUP>Srr比は0.704~0.717(εsr=-2.5~183.7)であった.<BR>Nd-Sr同位体比の変化は負の相関性をもち,地質と地理的特性により,Nd-Sr同位体組成は中生代慶尚堆積盆地の花崗岩と先カンブリア地域の花崗岩に分けられる.慶尚堆積盆地の白亜紀花崗岩のεNdは4.4~+0,4,初生87Sr/86Sr比0.704~0.706(εSr=-2.5~33.5)で,マントル起源花崗岩質マグマの特性を現らわす.また白亜紀花崗岩と密接に産する安山岩質岩の同位体組成(εNd=*12.6~-0.8,初生<SUP>87</SUP>Sr/<SUP>86</SUP>Srr比=0.705~0.707,εSr,=9.4~389)は花崗岩の同位体組成と類似し同源マグマ起源から由来したと考えられる.<BR>一方,中生代堆積盆地外側地域と沃川地向斜地域のジュラ紀花崗岩は,白亜紀のものより低いεNd値(-21.0~-13.6)と高い<SUP>87</SUP>Sr/<SUP>86</SUP>Srr初生値(0.711~0.717,εSr=97.3~183.7)をもち,著しい地殻物質の特徴を現わす.<BR>沃川地向斜地域の白亜紀花崗岩は慶尚堆積盆地の同時期花崗岩のNd,Sr同位体組成とは異なり,ジュラ紀花崗岩の同位体特性を現わす.それは花崗岩の貫入年代よりも地殻物質の同位体に富むマグマの起源によると考えられる.<BR>2ステージモデル年代は白亜紀花崗岩は0.5~1.1Ga,ジュラ紀花崗岩は1.6~2.2Gaがえられ,中生代深成岩類の起源物質はmid-Proterozoicにすでに進化したと考えられる.

Mesozoic granitic plutons in the Korean peninsula have εNd values ranging from -14.9 to +0.4 and initial<SUP>87</SUP>Sr/<SUP>86</SUP>Srr ratios from 0.704 to 0.717 (εSr=-2.5-183.7). The Nd and Sr isotopic variations in the granitic rocks are inversely correlated and are clearly divided into two distinct groups namely: a mantle type as in the Mesozoic Kyongsang basin and a crust type as in the Precambrian terranes, based on geologic and geographic differences. Cretaceous granitic rocks in the Kyongsang sedimentary basin have εNd of -4.4 to +0.4 and initial<SUP>87</SUP>Sr/<SUP>86</SUP>Srr ratios of 0.704 to 0.706 (εSr=-2.5-33.5), indicating derivatives of the mantle source. While, andesitic rocks in the basin have Nd-Sr isotopic compositions (EM=-12.6--0.8, (<SUP>87</SUP>Sr/<SUP>86</SUP>Srr)i=0.705-0.707, εSr= 9.4-38.9) similar with those of the Cretaceous plutonic rocks, implying cogenetic sources of the magma.<BR>On the other hand, Jurassic plutons from outside of the basin, including some Cretaceous granites in the Okchon geosynclinal zone, have much lower εNd of -21.0 to -13.6 and higher initial<SUP>87</SUP>Sr/<SUP>86</SUP>Srr ratios of 0.711 to 0.717 (εSr=97.3-183.7) than the Cretaceous plutons in the Kyongsang basin, which suggests a significant crustal assimilation or contamination of the granitic magma.<BR>The two stage model ages of the Cretaceous and Jurassic granite plutons were calculated to be 0.5 to 1.1 Ga and 1.6 to 2.2 Ga, respectively. This data suggests that the source materials of these Mesozoic plutons in the Korean peninsula have evolved considerably since mid - Proterozoic times.

収録刊行物

  • 資源地質  

    資源地質 46(4), 215-226, 1996-08-31 

    The Society of Resource Geology

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各種コード

  • NII論文ID(NAID)
    10002858848
  • NII書誌ID(NCID)
    AN10379890
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    09182454
  • NDL 記事登録ID
    4027657
  • NDL 雑誌分類
    ZM49(科学技術--地球科学--地質) // ZM46(科学技術--地球科学--岩石・鉱物・鉱床)
  • NDL 請求記号
    Z15-123
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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