S2: Water Rock Interaction (Special Session)

[S2-04] Effect of silica on iron partitioning during serpentinization

[Presentation award entry]

*Shuhei Tanaka¹, Atsushi Okamoto¹, Kazuki Yoshida¹, Yasuhiro Niwa^2,3, Masao Kimura^2,3, Masaoki Uno¹, Masakazu Fujii^4,5 (1. Tohoku Univ. Env., 2. IMSS, 3. KEK, 4. NIPR, 5. The Graduate Univ. for Advanced Studies)

Keywords:Serpentinization, Silica, Iron partitioning

Serpentinization of mantle peridotite, containing olivine (Ol) and orthopyroxene (Opx) involves oxidation of Fe and H₂ production. However, the effect of high silica activity by Opx reaction on iron partitioning and H₂ production is unclear. In this study, we conducted batch type experiments of Ol-H₂O and Ol-Opx-H₂O systems at 200-400℃. In Ol-Opx-H₂O system, Opx reacted selectively above 300℃, and little magnetite was produced. However, H₂ production rate was comparable to that of the Ol-H₂O system by Fe³⁺ in serpentine, indicating silica changed the mechanism of H₂ generation.