Paleozoic and Early Mesozoic Magmatism Manifestations in the Early Precambrian Structure of the South Yenisei Ridge

摘要

This study characterizes some issues of the Paleozoic and Mesozoic tectonomagmatic evolution of Precambrian structures from the southwestern margin of the Siberian craton. The relationship between the Devonian and Triassic magmatic events is demonstrated from the example of the Sevemaya rift-related structure, South Yenisei Ridge. U-Pb SHRIMP dating yielded ages of 387 ± 5 Ma for leucogranites and 240 ± 3 Ma for the overlying alkaline trachytes. These ages show good agreement with Ar-Ar geochronological data (392-387 Ma) obtained for micas from paragneisses and leucogranite dykes of the Yenisei suture zone, the extension of which is superimposed by the studied rift-related structure. The previous geological evidence and the Devonian age estimate first obtained for magmatic rocks of the Yenisei Ridge allow us to interpret the studied leucogranites as products of Devonian continental rifting, similar to volcanic and intrusive rocks of the North Minusa depression and Agul graben. Like other localities within the western margin of Siberian craton, the formation of Triassic alkaline rocks may be related to the Siberian superplume activity.