Three-Dimensional Numerical Simulation of Gas–Liquid Two-Phase Flow in the Izena Hole, Middle Okinawa Trough, to Clarify the Generation Process of Seafloor Hydrothermal Deposits

DOI Web Site 42 References Open Access
  • TOMITA Shohei Albert
    Geotechnical Engineering Department, Technology Research Institute, Obayashi Corporation
  • KOIKE Katsuaki
    Department of Urban Management, Graduate School of Engineering, Kyoto University
  • KASAYA Takafumi
    Submarine Resources Research Center, Research Institute for Marine Resources Utilization, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
  • GOTO Tada-nori
    Department of Life Science, Graduate school of Science, University of Hyogo
  • SUZUKI Katsuhiko
    Submarine Resources Research Center, Research Institute for Marine Resources Utilization, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

Bibliographic Information

Other Title
  • 海底熱水鉱床の生成プロセスの解明に向けた中部沖縄トラフ伊是名海穴での3次元気液二相流数値シミュレーション

Description

<p>Although seafloor hydrothermal deposits are essential metal resources because of their considerable reserves and high metal grades, the concrete physical setting that causes their generation remains unclear. These can be clarified only through numerical simulation studies because it is impossible to observe the physical setting and actual phenomena over a long period and a wide area below the seafloor. In this study, we attempted to clarify those by simulating a three-dimensional flow system of a gas–liquid two-phase fluid and regional temperature distribution in a hydrothermal field. The Izena Hole, middle Okinawa Trough, was selected as our target field. Results show that the ore bodies on and beneath the seafloor were generated by different mechanisms. In the early stage of hydrothermal activity, most of the hydrothermal fluids ascended freely from a great depth and spouted from the seafloor and consequently generated ore bodies on the seafloor by mixing with seawater. Over time, a hardly permeable cap layer was formed by hydrothermal alteration, which caused lateral fluid flows and inhibited the inflow of cold seawater under the cap layer, resulting in a temperature increase and consequent boiling of the fluids. Mineral replacement occurring in large amounts of lateral fluid flows over tens of thousands of years is the most likely cause of the generation of subseafloor ore bodies. Therefore, cap layer formation is an essential factor in generating subseafloor ore bodies and changing the location of the ore body occurrence from on to beneath the seafloor.</p>

Journal

  • Journal of MMIJ

    Journal of MMIJ 140 (6), 101-111, 2024-06-28

    The Mining and Materials Processing Institute of Japan

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