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

本文旨在阐明科马提岩在热液蚀变过程中成分的广泛变化及其长期变化对蛇纹化反应的影响。通过热力学模型计算，结合科马提石-水反应实验，得到以下结果。(1)在20 ~ 25 wt.%之间，蛇纹岩化过程中H_2的生成量变化剧烈科马提岩中的MgO。(2)Al_2O_3含量从Barberton型科马提岩到Gorgona型科马提岩的变化不影响蛇纹岩化过程中的产氢量。(3)蛇纹石化反应产生的H_2量在~350°C时达到峰值，并至少在400°C时保持在接近峰值的水平。这与橄榄岩的蛇纹岩化作用在~300°C时产生大量H_2，而在较高温度（特别是>350°C）时仅产生少量H_2的现象有明显区别。

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).