New U-Pb and Sm-Nd Data and REE Distribution in Sulphides of Paleoproterozoic PGE Layered Intrusions in the Arctic Part of the Fennoscandian Shield

摘要

The U-Pb (on zircon) and Sm-Nd analysis is a popular isotope-geochronological tool for estimating the age of rocks from PGE mafic-ultramafic intrusions. Sulphides can be used to study the geochronology of ore processes as well, since they should indicate the time of ore mineralization. Gabbronorite has been sampled from the Passivaara reef at the Penikat layered intrusion (Finland) for U-Pb and Sm-Nd isotope single zircon analyses in order to separate sulphide minerals. The Sm-Nd isotope age of gabbronorite has been dated at 2426 ± 36 Ma; eNd(T) = − 1.4 ± 0.4. The Sm-Nd isotope age on sulphides and rock-forming minerals reflects the crystallization time of the ore-bearing gabbronorite from the Passivaara reef of the Penikat layered intrusion. The mass-spectrometer analytical environment and modes of operation have been adjusted to detect REE in sulphide minerals on example of pyrite from the PGE Penikat layered intrusion (Finland) and chalcopyrite from the Talnakh deposit (Norilsk area, Russia) has been estimated. The total REE content in pyrite is ca. 3.5 ppm, which is enough to define the Sm-Nd age of pyrite. The study shows how to use the mineral/chondrite spectra to evaluate the accuracy of the REE analytical results on example of State Standard Sample 2463 (Russia).