This paper presents the results of the first executed physicochemical modeling of the interaction processes between gabbroids and serpentinites in mid-ocean ridges. The computer calculations were performed using the Selector software package for the temperature range from 100 to 1200degreesC and pressure of 500 atm at different water/rock ratios. It was determined that, during an injection of basic melt into serpentinites, magma is contaminated by ultramafic matter, whose crystallization results in the formation of a wide series of rocks from quartz-containing olivine gabbros to olivine gabbro-norites. At the exocontact of an intrusion, serpentinite is destructed to montmorillonite, over which amphiboles, brucite, periclase, clinozoisite, and calcite are formed. The data obtained are discussed in comparison with similar rock assemblages in ophiolites of the folded structures of the continents.

The Selector-S program complex was used to examine five models for the interaction of serpentinite with granitoids: serpentinite-quartz diorite, serpentinite-trondhjemite, serpentinite-granodiorite, serpentinite-calc-alkaline granite, and serpentinite-alkaline granite. The calculations were conducted for P = 0.3-1.0 kbar, T = 700-200degreesC, in the presence of aqueous and carbon dioxide fluid phases. The composition of the mineral assemblages newly formed in the outer-contact thermal field makes it possible to distinguish three zones: high-, medium-, and low-temperature. The dominant newly formed mineral of the former two zones is anthophyllite, while the mineral assemblage of the third zone corresponds to listwanite developing after serpentinite. The crystallization of minerals within the contact zone is demonstrated to depend on the major-element chemistry of the intruded granitoid melts, temperature, and the composition of the fluid, while independent of pressure.

Physicochemical models of the interaction between magnesium-rich basalts and seawater are discussed. It was found that the principal products of the changes in the basalt are minerals such as montmorillonite, serpentine, pectolite, and chlorite. The calculations are performed using the "Selector" software package for a temperature interval T = 25-350degreesC, P = 0.5 kbar, and different water-to-rock ratios. The analysis was implemented within the framework of two models describing the stage of the basalt consolidation and secondary heating related to the sinking of the products of the smectite facies formed over the consolidation period. The conclusion is reached that the magnesium-rich basalts represent the principal source for the serpentine encountered in ocean sediments. The data obtained are in good agreement with the experimental results and geological and petrographical observations.