The first isotopic data on the Paleoproterozoic age of the Serpovidnyi Ridge amphibolites, Keivy terrane, Baltic shield

摘要

This work presents the first data on the geochemistry, U-Pb (SHRIMP-II) age of zircon, U-Pb (conventional) age of titanite, Sm-Nd model age of whole rock samples, and age of reworking of metaporphyric rocks of the Serpovidnyi Ridge of the Keivy structure. These rocks are characterized by high contents of trace and rare earth elements indicative of an origin of the rocks from the enriched mantle source EM2. The negative E >(Nd) value (-2.4) does not exclude the contamination of mantle material. The age of two close periods is reliably identified: the crystallization of zircon (1740 +/- 15 Ma) and porphyroblastesis with the formation of plagioclase and epidote glomeroblasts combined with the crystallization of titanite (1719 +/- 13 Ma). The Sm-Nd isotope data indicate the Paleoproterozoic age of mafic volcanism in the Keivy terrane (2.37-1.77 Ga).