In order to date the cessation of magmatic activity and characterize the final stage of Paleozoic magmatism in the northeast Baltic Shield, we carried out isotope-geochemical investigation of dikes that are abundant within the Kola region. Alkaline dikes are complex objects for dating. They lack zircon but contain alien mantle material and lower crustal xenoliths. Moreover, they are characternized by postmagmatic alterations and wall-rock assimilation. Therefore, we used a combination of Rb-Sr and Sm-Nd isochron determinations (internal mineral isochron) and ⁴⁰Ar/³⁹Ar methods These methods are described.