Role of subducted sediments in the genesis of Kurile-Kamchatka island arc basalts : Sr isotopic and elemental evidence

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<sup>87</sup>Sr/<sup>86</sup>Sr ratios of ocean-floor sediments from the NW Pacific result from mixing between island-arc detritus (0.7037) and open-ocean detritus derived from the upper continental crust (0.7175). Sediments lying within and immediately in front of the Kurile-Kamchatka trench change from a c. 500 m sequence rich in open-ocean detritus in front of the south-central Kuriles to a c. 1000 m sequence, the Meiji sediment tongue, rich in island-arc detritus in front of the northern section of the arc. Overall, the sediments of this northern section have lower Th/U but higher K/Cs and Rb/Cs ratios, and these features are mirrored by all basalts from the northern section of the arc, presumably through sediment contamination of the subarc mantle sources. In detail, however, a simple mechanical addition of any type or mixture of known sediments to the sub-arc source mantle fails to reproduce the overall geochemistry of the arc basalts and selective transfer of mobile elements (Cs, Rb, K, Ba, Pb, Sr) and a low-<sup>87</sup>Sr/<sup>86</sup>Sr component (altered MORB, sub-arc mantle) seem required. Although <sup>87</sup>Sr/<sup>86</sup>Sr ratios of the bulk northern pre-arc sediments (0.7073) are lower than in the south-central section (0.7104), the flux of Sr into the subduction zone is thought to be greater in the north and could explain the higher <sup>87</sup>Sr/<sup>86</sup>Sr ratios of basalts from the northern section of the arc.

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  • Geochemical journal : journal of the Geochemical Society of Japan

    Geochemical journal : journal of the Geochemical Society of Japan 30(5), 289-321, 1996-10-01

    GEOCHEMICAL SOCIETY OF JAPAN

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各種コード

  • NII論文ID(NAID)
    10008801117
  • NII書誌ID(NCID)
    AA00654975
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    00167002
  • NDL 記事登録ID
    4080074
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z53-R488
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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