Sm-Nd AND U-Pb ISOTOPIC STUDY OF THE NYASYUKKA DIKE COMPLEX, KOLA PENINSULA, RUSSIA

Abstract

The Nyasyukka dike complex forms a NW-trending dike swarm in the Archean bedrock of the Murmansk Province adjacent to the Pechenga Complex. The dikes are mostly composed of two rock types, kaersutite-bearing peridotites and olivine gabbros. Also a rounded pyroxenite stock has been found in the area. The dikes were generated from ferropicritic parental magma which was similar to Pechenga ferropicrites though having a somewhat higher silica activity. A peridotite sample yielded an internal Sm-Nd isochron with an age of 1956 ± 19 Ma (MSWD = 0.7) and an initial 6Nd value of +1.4 ± 0.4. This is consistent with the baddeleyite age of 1941 ± 3 Ma, showing that the Nyasyukka dikes are ca. 40 Ma younger than the Pechenga ferropicrites. The pyroxenite stock shows geochemical and Nd isotopic evidence for significant crustal contamination. We also present isotopic and geochemical data for olivine gabbro-norite from the Tuloma River area, supporting the earlier view that there exist dikes of the Nyasyukka type in this area.

Keywords

• палеопротерозойская печенгская структура
• дайковый комплекс перидотитов-оливиновых габбро
• sm-nd и u-pb изотопные данные
• бадделеит
• циркон