THE U-PB AGE OF GRANITOIDS FROM THE NARODA PLUTON, THE NEAR-POLAR URALS

Abstract

The dating results enable to determine for the first time the probable formation sequence for I- and A-type granitoids. The former were forming during the whole time of the massif evolution, in homodromic sequence: quartz diorites→granodiorites→granites. Granites corresponding to A-types were formed at final stage, simultaneously with biotite granites of I-type. The time range for granitoids formation is near 33 mln years. The found evolution duration for Naroda pluton agrees with the known estimates of large-volume granite magma sources - 106-107 mln years.