S-granites of the Izhma zone of the Pechora basin basement: features of composition, U-Pb and 40Ar-39Ar dating results

Granites recovered by boreholes 1-Yuzhnaya Bolotnaya and 1-Sosyanskaya in the Izhma zone of the Timan megablock of the Pechora basin basement are most similar in their mineral and chemical composition to S-type granites. U-Pb (SIMS SHRIMP-IIe and SHRIMP-RG) zircon studies of these granitoids have not allowed for a correct determination of the rock formation time, as the zircons are either inherited or highly discordant. The granite age has been revised by the 40Ar-39Ar dating of muscovite from the same samples. The 40Ar-39Ar age of muscovite in granites of the 1-Yuzhnaya Bolotnaya borehole is 548 ± 7 Ma and in the 1-Sosyanskaya borehole is 565 ± 7 Ma. These data correlate with U-Pb (SIMS SHRIMP-IIe and SHRIMP-RG) ages on zircons from granites of other zones of Pechora basin basement and confirms the large-scale intrusion of granitoids in the Late Vendian during collision processes at the final stage of Timanian tectogenesis.