The age of the ferropicritic volcanics and comagmatic Ni-bearing intrusions at Pechenga, Kola Peninsula, USSR

Abstract

Sm-Nd, Pb-Pb and U-Pb isotopic results are presented for samples from the Pilgujarvi Suite of the Pechenga Series. Whole rock samples and clinopyroxenes of ferropicritic volcanics yield a Sm-Nd isochron age of 1990 ± 66 Ma with εNd + 1.6 ± 0.4. This age is also supported by the Pb-Pb data on ferropicrites, although the Pb isotopic system was partly disturbed by secondary processes. One 90% concordant U-Pb zircon analysis from a felsic metasediment indicates a minimum age of 1970 Ma for the deposition. Our isotopic results along with previous geochemical data support the view that the ferropicritic volcanics and the Ni-bearing gabbro- wehrlite intrusions are coeval and have similar source characteristics. -from Authors