抄録
Magmatic hydrothermal solution is formed as a consequence of crystallization of magmas at shallow crust. The ascending magmatic hydrothermal fluid through the crust inevitably experiences large pressure and temperature changes. Pressure-temperature condition of the magmatic hydrothermal system overlaps with the subcritical region of NaCl-H2O system, and the phase separation is regarded as a common and important differentiation process of the fluids. Since compressibility and thermal expansibility of hydrothermal fluids are large at high temperature and low pressure condition, large pressure and temperature dependence of equilibrium constants is expected in the P-T regions of the system. Large variations in the appearance of magmatic hydrothermal system are concluded to be due to the phase separation and the reactions with large pressure and temperature dependence under the large pressure and temprature gradients.
