Modeling mineral/solution interactions: The thermodynamic and kinetic code KINDISP

Abstract

Abstract The kinetic and thermodynamic geochemical model KINDISP (KINetics of DISsolution and Precipitation) describes the interactions between minerals and aqueous solutions, taking into account the irreversible dissolution of the reactants and the reversible precipitation of secondary products. The general laws included in the model are based on the theory of the Thermodynamics of Irreversible Processes. The water/rock interactions at low temperature are interpreted in a classical manner with the help of the Theory of the State of Transition and the chemistry of surface coordination. The mechanism which limits the rate of mineral dissolution or precipitation, the slowest one in successive irreversible reactions, is represented either by the aqueous molecular diffusion of an elementary entity (atom, molecule, etc.) or by the surface reaction in a broad sense. At each step of the calculation, KINDISP computes the reaction rates for each mineral reacting in the system and selects the slowest rate to represent the dissolution or precipitation law in this phase. The growth of secondary minerals is simulated in the domain of oversaturation (in nonequilibrium) after a nucleation step. The KINDISP model already has been used to simulate natural or induced water/rock interactions, not only at low temperatures, for example to study the effects of acid rain on surface weathering of a granite formation, estimate the formation time of a laterite layer, and the effects of pollution on the environment, but also at higher temperatures, for example to describe and account for diagenetic reactions in sedimentary basins for the purpose of exploiting the reservoirs as well as to study a system of hydrothermal reactions caused by heat storage or disposal of nuclear waste packages.