The bedrock in northernmost Sweden comprises Archaean (2.8–2.65 Ga) and Karelian (2.4–1.96 Ga) rocks and a volumetrically dominant population of magmatic rocks which formed during the Svecofennian (1.9–1.8 Ga) stage. New Ar–Ar (hornblende and muscovite) and U–Pb (zircon and monazite) isotopic results from representative lithologies are used to shed further light on the geological evolution. With respect to the Ar–Ar isotopic system, somewhat variable dates (hornblende) are interpreted as cooling ages that indicate different uplift histories, following a 1.8 Ga metamorphic peak, at different sides of the Karesuando-Arjeplog deformation zone. Other post-1.7 Ga 40Ar/39Ar ages are suggested to reflect either a neocrystallisation (muscovite) or an event leading to isotopic resetting (hornblende). It is suggested that post-1.76 Ga crustal processes have influenced the Ar–Ar mineral systems during three relatively short-lived (a few tens of million years) stages; peaking at ~ 1.73 Ga, ~ 1.63 Ga and ~ 1.55 Ga. Tentatively, the timing of these stages is coupled with far-field effects that elsewhere are associated with the alkali-rich granitic magmatism forming part of the Transscandinavian Igneous Belt (the 1.73 Ga event) and Rapakivi massifs (the 1.63 and 1.56 Ga events). It is proposed that the N-S to NW–SE orientation of these vast, regional granitic complexes matches that of major deformation zones in northernmost Fennoscandia and that locally initiated hydrothermal fluids followed weakness zones in the crust and ultimately led to element mobilisation, new mineral growth and isotopic over-printing preferentially affecting shear- and ore zones.