Abstract
Based on the thermochemical data for hydrolysis of a variety of rock-forming minerals (HELGESON, 1969), possible reactions between rocks and seawater at elevated temperatures have been examined. The result reveals that most of natural rock alteration facies can well be explained by the interaction of rocks with seawater at ordinary hydrothermal temperatures. This is consistent with the hypothesis that the hydrothermal ore-forming solution responsible for the Kuroko type mineralization in Japan might have been derived essentially from the coeval seawater (KAJIWARA, 1973a and 1973b). It is suggested that such cyclic seawater would also be essential to the regional metamorphic processes in the earth's crust. Available hydrogen isotope data for hydrated silicate minerals from some igneous and metamorphic rocks may also be interpreted with this view.
