Ar + and Kr + ion beams from the Jordan Van de Graaff Accelerator were utilized to irradiate thin films of Au-Ge, Ag-Ge and Cu-Ge systems at room temperature. Electrical resistivity measurements and backscattering spectrometry were employed as probes to investigate the kinetics of ion mixing, i.e. the formation of solid solutions in these systems. Despite the fact that the available model of Riviere and Jaouen on the kinetics of ion mixing was originally applied to multilayer systems, its application to bilayer systems under this investigation proved to work reasonably well. In addition, in this work, we present a new approach for the analysis of the relative contributions of the ion mixing mechanisms involved. It is found that both primary collisions and collisional cascade mechanisms contribute to ion mixing. In some cases, the effect of demixing is shown to exist and is attributed to primary collisions with the target atoms.