2017 年 51 巻 3 号 p. 103-118
A seafloor hydrothermal fluid circulation system develops beneath the seafloor where a magma as heat source and fault systems as fluid conduits are equipped. Seafloor hydrothermal systems act as important intermedia among the lithosphere, hydrosphere and biosphere. Seawater entrained into the seafloor evolves to the vent fluid that exit smokers or chimneys, through the processes during the fluid circulation such as elemental exchanges by water-rock interactions and involvement of magmatic volatiles. These interactions cause hydrothermal alteration of the lithosphere, looking from the opposite perspective. Chemical species dissolved in the vent fluids provide energy sources for biosphere around and beneath the seafloor of hydrothermal fields. Geochemical flux transported into the deep ocean by hydrothermal plumes affects chemical and biological processes in the hydrosphere. Formation of mineral deposits from the hydrothermal fluids leads concentration of specific metal elements resulting from long duration of hydrothermal activity. As hydrothermal vent sites have been discovered ubiquitously in various geologic settings, their diversity especially in geochemical aspects becomes more noticeable and interesting.
