日本列島付加体中に胚胎する古海洋底で生成した鉱床  [in Japanese] Ore deposit formed on a paleo-seafloor in the Japanese accretionary complex  [in Japanese]

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Author(s)

    • 野崎 達生 Nozaki Tatsuo
    • 海洋研究開発機構海底資源研究開発センター|東京大学大学院工学系研究科エネルギー・資源フロンティアセンター|神戸大学大学院理学研究科惑星学専攻|千葉工業大学次世代海洋資源研究センター Research and Development (R&D) Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)|Frontier Research Center for Energy and Resources (FRCER), The University of Tokyo|Department of Planetology, Kobe University|Ocean Resources Research Center for Next Generation (ORCeNG), Chiba Institute of Technology
    • 藤永 公一郎 Fujinaga Koichiro
    • 東京大学大学院工学系研究科エネルギー・資源フロンティアセンター|千葉工業大学次世代海洋資源研究センター Frontier Research Center for Energy and Resources (FRCER), The University of Tokyo|Ocean Resources Research Center for Next Generation (ORCeNG), Chiba Institute of Technology
    • 加藤 泰浩 Kato Yasuhiro
    • 海洋研究開発機構海底資源研究開発センター|東京大学大学院工学系研究科エネルギー・資源フロンティアセンター|千葉工業大学次世代海洋資源研究センター|東京大学大学院工学系研究科システム創成学専攻 Research and Development (R&D) Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)|Frontier Research Center for Energy and Resources (FRCER), The University of Tokyo|Ocean Resources Research Center for Next Generation (ORCeNG), Chiba Institute of Technology|Department of Systems Innovation, The University of Tokyo

Abstract

<p>日本列島は主に過去4億年以降の付加体から構成されており,付加体中には古海洋底で生成した様々な鉱床が胚胎している.本論文では,別子型硫化物鉱床,層状鉄マンガン・マンガン鉱床に関する成因論の進展と未解明の課題をレビューする.三波川帯に分布する別子型鉱床は遠洋域の中央海嶺で生成し,ジュラ紀後期海洋無酸素事変によって保存された.現地性緑色岩を伴う四万十帯北帯の別子型鉱床は,白亜紀後期の海嶺沈み込み現象に付随して生成した.他のメランジュ中に胚胎する別子型鉱床については未解明の点が多い.層状鉄マンガン鉱床は,中央海嶺近傍の熱水性堆積物を起源とし,緑色岩を伴う層状マンガン鉱床は海山近傍の熱水性堆積物に由来する.チャート中に胚胎し緑色岩を伴わない層状マンガン鉱床は,貧酸素・高マンガンの深層水に高酸素・貧シリカの表層水流入によって形成したと考えられるが,マンガンの究極的な起源についてはいまだ不明である.</p>

<p>Basement rocks of the Japanese islands consist mainly of accretionary complexes younger than ca. 400 Ma. Various types of stratiform and/or massive ore deposits that formed on a paleo-seafloor are hosted within the Japanese accretionary complexes. In the present study, we review recent progress on metallogenetic research and outline unsolved problems related to these types of deposits, such as the Besshi-type sulfide deposits, bedded ferromanganese deposits, and bedded manganese deposits related/unrelated to greenstone. Besshitype deposits within the Sanbagawa Belt formed by vigorous hydrothermal activity at a pelagic mid-ocean ridge during the Late Jurassic, and sulfide ore was preserved by the concomitant Late Jurassic Ocean Anoxic Event. Besshi-type deposits, which are closely associated with <i>in-situ</i> greenstone in the Northern Shimanto Belt, formed by ridge subduction during the Late Cretaceous. Certain aspects of the genesis of other Besshi-type deposits in the mélange zone of the Northern Shimanto and Chichibu Belts remain unresolved, although the Tsuchikura deposit occurs as an olistolith. Bedded ferromanganese deposits, so-called umber deposits, are derived from hydrothermal sediments at the periphery of the mid-ocean ridge, whereas bedded manganese deposits closely associated with greenstones were originally produced as hydrothermal sediments around seamounts. Bedded manganese deposits that occur within pelagic chert sequences without greenstone are considered to be formed by drastic changes in the redox state of deep water due to the influx of oxic and silicapoor surface seawater into anoxic and high-manganese stagnant deep water. However, whether bedded manganese deposits without greenstone are hydrothermal or hydrogenous in origin remains controversial. Although the problems are complex, future multi-disciplinary research should clarify many of the unsolved questions related to metallogenesis.</p>

Journal

  • The Journal of the Geological Society of Japan

    The Journal of the Geological Society of Japan 124(12), 995-1020, 2018

    The Geological Society of Japan

Codes

  • NII Article ID (NAID)
    130007614622
  • NII NACSIS-CAT ID (NCID)
    AN00141768
  • Text Lang
    JPN
  • ISSN
    0016-7630
  • NDL Article ID
    029440730
  • NDL Call No.
    Z15-174
  • Data Source
    NDL  J-STAGE 
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