Recent Modeling Studies of Seafloor Hydrothermal Systems

概要

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We briefly review modeling studies of subseafloor hydrothermal systems. We discuss critical properties of water, phase separation of seawater, and precipitation of minerals, which are important for the circulation pattern of hydrothermal systems. Physical properties of water drastically change around its critical point. They confine the width of upwelling plumes, and keep the maximum temperature of hydrothermal fluids in the range of 350∿400°C. Seawater separates into two phases with different salinities, when it is heated. This is the major reason for the salinity variation of hydrothermal fluids. High salinity fluids sink to form a stagnant layer beneath the vigorously convecting fluid layer. Since the stable stratification in the brine layer decreases the heat transfer, the heat output from the hydrothermal system with a brine layer is less than that without one. Precipitation and dissolution of minerals occur when the temperature of the fluid changes and when two compositionally different fluids mix. Precipitation decreases pore space the crustal rocks, and obstructs flow paths. Another role of precipitation is to stabilize the circulation by preventing two different fluids from mixing.
日本海洋学会の論文