風化および熱水変質条件における鉱物の安定領域

水の活動度とギブス生成自由エネルギー値変化による移動

抄録

Many thermodynamical interpretations are used in the study of weathering and hydrothermal alteration. In the simulation of the mechanism of alteration, it is necessary to introduce the factors of physical properties. We investigated the changes in the stability fields of several minerals in detail by the introduction of the parameter of pore size. (1) By assuming that the form of pore of rock or mineral is tubular, the pressure condition at the interface between solid and water change's as a function of diameter of the pore. (2) Water activity changes variedly by the given pressure and temperature. Water activity has been obtained as a function of diameter of pore in rock or mineral. (3) When the water activity changes, the stability field of each chemical species shift the phase boundaries (4) The values of thermochemical data, in particular Gibbs free energy of formation, differ with sources, so that the thermodynamical study on weathering and hydrothermal alteration needs the greatest care with respect to the change in water activity. These results are obtained for the system of K₂O-Al₂O₃-SiO₂-H₂O.