Quantitative elucidation of "Komatiite-water interaction" as a key process of early life evolution

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The aim of this study was to elucidate the effect of wide compositional variation and its secular change on serpentinization reaction of komatiite during hydrothermal alteration. Based on thermodynamic model calculation with komatiite-water reaction experiment, the following results were obtained. (1) Generation of H_2 during serpenitization is drastically changed between 20 and 25 wt.% MgO in komatiite. (2) Variation of Al_2O_3 content from Barberton-type komatiite to Gorgona-type komatiite does not affect to amounts of H_2-generation during serpentinization. (3) Amounts of H_2 generated by serpenitization reaction reach a peak at ～350°C and are maintained at close to the peak level, at least, up to 400°C. This is significantly different from serpentinization of peridotite, which produce large amounts of H_2 at ～300°C but only small amounts of H_2 at higher temperatuers (especially >350°C).