海底熱水系の固体・流体相互作用に関する同位体的研究

抄録

Seafloor hydrothermal systems have played an important role in the Earth’s evolution at sites where interaction between lithospere and hydrosphere occurs using Earth’s internal energy as a heat source. Reaction between oceanic crustal rock and fluid that is derived from the seawater under high temperature and pressure conditions results in efficient transport of thermal energy and in significant changes in chemical composition. Alkaline hydrothermal systems seem to be more favorable conditions for the occurrence and evolution of Earth’s early life, because of the higher thermal stability of amino acids. Boron isotope can be a new useful proxy of fluid-rock interaction in hydrothermal systems. Combination of boron isotope with existing conventional proxies can elucidate sub-seafloor fluid-rock reactions in detail, such as hydrothermal alteration of lower oceanic crust and multi-stage alterations related to sulfide ore deposit formation.