Abstract
Hydrothermal flux from mid-oceanic ridges and back arc basins influences global seawater chemistry. For instance, Mg problem (Dreyer, 1974) can be solved by taking into account of Mguptake from seawater due to the interaction of seawater with oceanic crust under hydrothermal conditions. SO42-also removes considerably from seawater to oceanic crust. Ca, Si and K transfer from oceanic crust to seawater. This interaction takes place not only at mid-oceanic ridge axis, but also at mid-oceanic ridge flank system. The influence of hydrothermal flux from present-day back arc basins on seawater chemistry is small, compared with that of midoceanic ridges. However, hydrothermal flux from back arc basins in Circum Pacific region during middle Miocene (25-15 Ma)(e. g. Green tuff activity) is large. Especially, hydrothermal fluxes of volatile elements (S, As, Sb, Bi, Cl) from back arc basins are large, compared with the hydrothermal fluxes from mid-oceanic ridges. It is concluded that global seawater chemistry is controlled not only by exogenic processes (e. g. river input, sedimentation) but also by endogenic processes (e. g. hydrothermal activity).
