The main features of the theory of metasomatic zoning, developed by the author, are here exposed. The basic differential equations of metasomatic zoning, of the infiltration as well as of the diffusion type, are deduced for the conditions of local equilibrium, the kinetic phenomena being neglected. The sharpness of the fronts of replacement and other regularities of metasomatic columns are established and the differences between infiltration and diffusion columns are shown. The mathematical model of the “outstripping wave of acidic components” in the flow of postmagmatic solutions is discussed, in relation with the “acidic filtration effect”, i.e., with the higher filtration rate of acidic components as compared with basic ones. The passage of this acidity wave causes the acid leaching of metals out of rocks and their subsequent concentrated redeposition in veins. One may therefore speak of a lateral and vertical hydrothermal acid-base differentiation.