Paleozoic and early mesozoic magmatism manifestations in the early Precambrian structure of the South Yenisei Ridge

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 Severnaya 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.     

Magmatism evolution and carbonatite-granite association in the neoproterozoic active continental margin of the Siberian craton: Thermochronological reconstructions

Neoproterozoic carbonatites and related igneous rocks, including A-type granites in the Tatarka-Ishimba suture zone of the Yenisey Ridge are confined to a horst-anticlinal structure that was formed in a transpression setting during the oblique collision between the Central Angara terrane and the Siberian craton. The carbonatites, associating mafic (including alkaline) dikes as well as the Srednetatarka nepheline syenites are the oldest igneous formations of the Tatarka active continental margin complex. Geochronological data indicate that magmatic evolution continued in the studied anticline for nearly 100 m.y. On the earliest stage carbonatites were formed and on the last stage — the emplacement of mantle-crustal A-type Tatarka granites took place. According to new U/Pb zircon studies, the earliest rocks in the Tatarka pluton are A-type leucogranites aged 646 ± 8 Ma. The younger ⁴⁰Ar/³⁹Ar ages of carbonatites obtained for phlogopites (647 ± 7 and 629 ± 6 Ma) are related to the last tectonic events in the studied region of the Tatarka-Ishimba suture zone, which are coeval with the formation of the A-type granitoids (646–629 Ma).     

The oldest island arc complex of Taimyr: Concerning the issue of the Central-Taimyr accretionary belt formation and paleogeodynamic reconstructions in the arctic

In this paper we provide data on the oldest island arc complex of Taimyr, which was established within the Central-Taimyr accretionary belt. We demonstrate its relationship with the mainly turbiditic back-arc basin complex. U-Pb isotopic data for zircons are presented from a plagiogranite and a plagiorhyodacite, indicating that the island arc formed 961–969 m.y. ago from a substance with a Mezoproterozoic model age: T _Nd(DM) varies from 1170 to 1219 Ma. Paleomagnetic investigations performed on the island arc complex rocks showed that the paleomagnetic pole of the island arc is close to synchronous poles, obtained for the south-east of the Siberian craton. Consequently, the island arc whose relicts are preserved in the modern structure of the Three Sisters Lake region was located in close proximity to the Taimyr margin of Siberia at the moment of its formation and could be separated from the continent by a back-arc basin. The data obtained have a fundamental significance for geodynamic paleoreconstructions in the Arctic sector for the Neoproterozoic.