The results of geochronological and petrological studies of the largest mafic dyke in the northern part of the Fennoscandian Shield, called the Great Dyke of the Kola Peninsula (GDK), are presented. According to baddeleyite U-Pb ID-TIMS age data, the GDK crystallization age is 2680 ± 6 Ma. The age of host granites is 2.75–2.72 Ga (U-Pb, zircon, SHRIMP-II). The dyke has a simple internal structure with no signs of multistage melt injection. It comprises uniform-grained and plagioclase-porphyritic dolerites and gabbro that are amphibolitized to varying degrees. All rocks are low-Mg (Mg# less than 0.37) with low concentrations of Cr and Ni, and present a result of differentiation of more primitive melts. The analysis of geochemical and Sr‑Nd isotopic data suggests that GDK melts could be formed by mixing of two types of mantle melts: depleted asthenospheric and enriched melts formed via melting of a lithospheric mantle. The weakly fractionated HREE spectra indicate that primary GDK melts originated at shallow (<60 km) depths outside the garnet stability field. The generation and injection of melts of the Neoarchean GDK occurred immediately after the of large-scale granitic magmatism and main crust-forming event in the Murmansk Craton and marked the cratonization of the continental lithosphere in the northeastern part of the Fennoscandian Shield.