Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge |
| |
| Authors: | S Kawagucci J Miyazaki T Noguchi K Okamura T Shibuya T Watsuji M Nishizawa H Watanabe K Okino N Takahata Y Sano K Nakamura A Shuto M Abe Y Takaki T Nunoura M Koonjul M Singh G Beedessee M Khishma V Bhoyroo D Bissessur L S Kumar D Marie K Tamaki K Takai |
| |
| Institution: | 1. Department of Subsurface Geobiological Analysis and Research (D‐SUGAR), Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, Japan;2. Research and Development Center for Submarine Resources, Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, Japan;3. Laboratory of Ocean‐Earth Life Evolution Research (OELE), Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, Japan;4. Center for Advanced Marine Core Research, Kochi University, Nankoku, Japan;5. Marine Technology and Engineering Center (MARITEC), Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, Japan;6. Department of Marine Biodiversity Research, Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, Japan;7. Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwanoha, Kashiwa, Japan;8. Department of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Tokyo, Japan;9. Research and Development Center for Marine Biosciences, Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, Japan;10. Albion Fisheries Research Centre, Petite Rivie‘re, Mauritius;11. Mauritius Oceanography Institute, Morcellement de Chazal, Albion, Mauritius;12. Ministry of Agro‐Industry, Food Production and Security, Port Louis, Mauritius;13. School of Engineering, Frontier Research Center for Energy and Resources (FRCER), The University of Tokyo, Tokyo, Japan |
| |
| Abstract: | Fluid chemistry and microbial community patterns in chimney habitats were investigated in two hydrothermal fields located at the Central Indian Ridge. Endmember hydrothermal fluid of the Solitaire field, located ~3 km away from the spreading center, was characterized by moderately high temperature (307°C), Cl depletion (489 mm ), mildly acidic pH (≥4.40), and low metal concentrations (Fe ≤ 105 μm and Mn = 78 μm ). Chloride depletion indicates that the subseafloor source fluid had undergone phase separation at temperatures higher than ~390°C while the metal depletion was likely attributable to fluid alteration occurring at a venting temperature of around 307°C. These different temperature conditions suggested from fluid chemistry might be associated with an off‐spreading center location of the field that allows subseafloor fluid cooling prior to seafloor discharge. The microbial community in the chimney habitat seemed comparable to previously known patterns in typical basalt‐hosted hydrothermal systems. Endmember hydrothermal fluid of the Dodo field, standing on center of the spreading axis, was characterized by high H2 concentration of 2.7 mm . The H2 enrichment was likely attributable to fresh basalt–fluid interaction, as suggested by the nondeformed sheet lava flow expansion around the vents. Thermodynamic calculation of the reducing pyrite–pyrrhotite–magnetite (PPM) redox buffer indeed reproduced the H2 enrichment. The quantitative cultivation test revealed that the microbial community associated with the hydrothermal fluid hosted abundant populations of (hyper)thermophilic hydrogenotrophic chemolithoautotrophs such as methanogens. The function of subseafloor hydrogenotrophic methanogenic populations dwelling around the H2‐enriched hydrothermal fluid flows was also inferred from the 13C‐ and D‐depleted signature of CH4 in the collected fluids. It was observed that the hydrothermal activity of the Dodo field had ceased until 2013. |
| |
| Keywords: | Central Indian Ridge deep‐sea hydrothermal system fluid– rock interaction hydrogen microbiological characterization |
|
|
