The First U-Pb (SHRIMP II) Evidence of the Franklin Tectonic Event at the Western Margin of the Siberian Craton

摘要

Geochemical and isotope-geochronological evidence of Late Riphean intraplate magmatism within the Chernorechenskii massif at the western margin of the Siberian Craton has been obtained. These rocks crystallized from high-temperature and water-unsaturated magmas with a high content of alkalis, iron, and most noncoherent elements, which is typical of anorogenic A-type granites of intraplate settings. Their U-Pb age is 723 +/- 6 Ma, coeval to the Franklin rifting event widespread in the north of Laurentia, which is associated with the break-up of Rodinia. The simultaneity of the magmatic activity and concomitant rifting, as well as a similar sequence of analogous tectonothermal events at the Arctic margin of Rodinia, confirms modern paleoreconstructions, suggesting the territorial proximity of Siberia and the cratons of the North Atlantic at that time.