Certain features in large layered intrusions suggest that infiltration-driven metasomatic reactions or other post- solidification processes have played a central role in influencing the final distribution of mineral and chemical components. Features of this kind, recently recognized in the Skaergaard Intrusion, include: a. concretion-like masses of mafic minerals in a felsic matrix; b. irregularly shaped residual islands of earlier rock within a more felsic recrystallized domain; and c. multiply-fingered dendrites of plagioclase-rich rock within a more iron-rich matrix. Phenomena of this kind have also been observed in recent simulations of the reaction/transport equations for water-rock systems. We propose to use modeling to explain the origins of these recrystallization phenomena and to predict other possible post- solidification transformations. Processes to be accounted for in these simulations include grain growth and dissolution, solute diffusion and infiltration transport, fluid flow, and pressure solution. Because our models show that these phenomena occur under well-defined conditions, we shall use the results of the models to interpret commonly observed features in the Skaergaard and other large layered intrusions.
