P–T evolution of ultrahigh temperature metamorphism: Evidence for a Late Paleoproterozoic intraplate extension at the southwestern margin of the Siberian Craton

Occurrences of ultrahigh-temperature (UHT) granulite metamorphism of metapelites of Fe–Al composition were originally discovered on the Yenisei Ridge. Three stages of the evolution of the mineral associations were distinguished: (M1) pre-peak (840°C/7 kbar), (M2) culmination UHT (930°C/8 kbar), and (M3) post-peak (810°C/6.5 kbar) with subisobaric cooling. The “counterclockwise” evolution of the P–T parameters of rock metamorphism provides evidence for the formation of UHT parageneses in the tectonic environment of intraplate extension accompanied by the processes of underplating of mantle melts.