Major and trace element compositions and resource potential of ferromanganese crust at Takuyo Daigo Seamount, northwestern Pacific Ocean

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Author(s)

    • Nozaki Tatsuo
    • 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), School of Engineering, The University of Tokyo|Department of Planetology, Graduate School of Science, Kobe University
    • Tokumaru Ayaka
    • Research and Development (R&D) Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)|Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo
    • Takaya Yutaro
    • 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), School of Engineering, The University of Tokyo|Department of Resources and Environmental Engineering, School of Creative Science and Engineering, Waseda University
    • Kato Yasuhiro
    • 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), School of Engineering, The University of Tokyo|Department of Systems Innovation, School of Engineering, The University of Tokyo
    • Suzuki Katsuhiko
    • Research and Development (R&D) Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
    • Urabe Tetsuro
    • Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo

Abstract

<p>We report major element and trace element compositions of ferromanganese crusts (Fe-Mn crusts) on Takuyo Daigo Seamount, northwestern Pacific Ocean. Highly enriched elements in these crusts, such as Co (6500 ppm), Ni (4000 ppm), Mo (520 ppm), Te (39 ppm), W (92 ppm), Pt (0.19 ppm), and rare earth elements (REEs; ∑REE = 1700 ppm), exhibit strong positive correlations with either Fe or Mn concentrations. Chemical analyses of the crusts show that the Fe/Mn ratio decreases toward shallower water and older deposits. Thus, deeper or younger crust is more promising as a REE (other than Ce) resource, and shallower or older crust has a greater potential as Co, Ni, Ce, and Pt resources. REE profiles of Fe-Mn crusts with less than 0.5 wt% P, normalized to post-Archean average Australian shale, are flat with positive Ce anomalies whereas samples with more than 0.5 wt% P are enriched in heavy REE, and four samples from deep in the crusts with more than 2.2 wt% P do not exhibit positive Ce anomalies. These differences in REE patterns can be explained by mixing of Fe-Mn oxide and Ca-phosphate minerals (apatite). Assuming that Fe-Mn crusts with 5 cm thickness and 1.29 g/cm<sup>3</sup> dry density are homogeneously distributed at water depths from 1000 to 3000 m along the 500 km perimeter of Takuyo Daigo Seamount, the possible reserve represented by Fe-Mn crusts is roughly 65 Mt of ore. Based on the average concentrations obtained here, resource amounts at Takuyo Daigo Seamount are 420 × 10<sup>3</sup> t Co, 110 × 10<sup>3</sup> tREO, 2500 t Dy, and 440 t Tb, comparable to the known reserves of major mineral producing nations. Thus, Fe-Mn crusts in the northwestern Pacific Ocean have a notable potential as a source of Co.</p>

Journal

  • GEOCHEMICAL JOURNAL

    GEOCHEMICAL JOURNAL 50(6), 527-537, 2016

    GEOCHEMICAL SOCIETY OF JAPAN

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