Resumo
The isotopic age of rocks from the clinopyroxenite-wehrlite Porya Guba Complex hosting the Kolvitsa Fe-Ti-V deposit was determined for the first time. Sm–Nd age of the barren clinopyroxenites prevailing in a studied massif is 1858 ± 34 Ma (εNd(T) = –1.5) and is considered as the emplacement time of the Porya Guba Complex, occurred after the peak of granulite metamorphism (1925–1915 Ma). Quenching zones found around xenoliths of granulites in clinopyroxenites indicate the emplacement of the complex into the cooled rocks of the Lapland-Kola orogen, which is consistent with the estimated time of its cooling (1880–1870 Ma, 450°, by rutile). Mineralized rocks, as inferred from active assimilation of granulite xenoliths, are formed at a late stage of the complex development: the age of mineralized pyroxenites enriched in platinum and palladium (0.8 g/t) is 1832±35 Ma (εNd(T) = –2.0), while the age of titanomagnetite ore is 1823 ± 19 Ma (εNd(T) = –2.5). Thus, the obtained isotopic data indicate that the emplacement of small ultramafic intrusions developed in the Kandalaksha-Kolvitsa granulites (Kolvitsa Melange) took place during the cooling stage of the Lapland-Kola orogen.