多段階の堆積サイクルを経た堆積物・堆積岩における源岩の初期Sr同位体比の保持―淡路島の細粒河川堆積物を例に―

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  • 太田 充恒
    国立研究開発法人産業技術総合研究所地質調査総合センター
  • 南 雅代
    名古屋大学宇宙地球環境研究所年代測定研究部

書誌事項

タイトル別名
  • Retentive primary Sr isotopic ratio of source rock to sediment and sedimentary rock through multistage sedimentary cycles: Case study of stream sediments in Awajishima Island
  • タダンカイ ノ タイセキ サイクル オ ヘタ タイセキブツ ・ タイセキガン ニ オケル ゲンガン ノ ショキ Sr ドウイタイヒ ノ ホジ : アワジシマ ノ サイリュウ カセン タイセキブツ オ レイ ニ

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説明

<p>We have elucidated retention of primary Sr isotopic ratios in source rocks to sediments and sedimentary rocks during repeated sedimentation recycling. Twenty-three fine stream sediments (<180 μm) in Awajishima Island were used for the study. The 87Rb/86Sr and 87Sr/86Sr of stream sediments originated from Cretaceous Ryoke granitic rocks and Cretaceous sedimentary rocks (Izumi Group) were similar to those of the respective source rocks. Incidentally, the 87Rb/86Sr-87Sr/86Sr of stream sediments in Awajishima Island suggests that Cretaceous felsic igneous rocks are the dominant source of clastics in Izumi Group. Stream sediments derived from Neogene and Quaternary sediments, which are originated from granitic rocks and Izumi Group, had comparable isotopic ratios to those of the respective primitive source rocks. Accordingly, 87Rb/86Sr and 87Sr/86Sr can be retained during the repeated recycling process of sediments and sedimentary rocks. Stream sediment is presumed to consist of clastics supplied from respective lithologies according to their exposed areas. However, 87Sr/86Sr of stream sediment is not comparable to the values calculated from exposed areas of lithologies and isotopic data of parent rocks. The result suggests that amount of sedimentation denudation and production differs among different lithologies and is not simply proportional to their exposed areas.</p>

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  • 地球化学

    地球化学 53 (2), 59-70, 2019-06-25

    一般社団法人日本地球化学会

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