This report presents results of isotopic studies of the Eye-Dashwa Lakes pluton, located near Atikokan, Ontario. Suites of pristine 'unaltered' and 'highly altered' core samples from deep boreholes were used to study Rb-Sr, U-Th-Pb and Sr-Nd systematics, whole-rock Pb isotopes and fission track dating of apatite. The results have been used to investigate natural analogues for radionuclide migration in the geosphere, the tectonic stability of the pluton and the extent of water-rock interaction in fracture zones.