Neoproterozoic tectonic structure of the Yenisei Ridge and formation of the western margin of the Siberian craton based on new geological, paleomagnetic, and geochronological data

摘要

There are continuing issues concerning the formation and reconstruction of the geographic position of the Neoproterozoic Yenisei Ridge-a key element of the western framing of the Siberian craton and the Central Asian orogenic belt. This study focuses on the inner structure, composition, and boundaries of the Central Angara terrane, which is the largest in the Transangarian segment of the Yenisei Ridge. We propose a scheme of fault deformation of the region and demonstrate that the fault tectonics of the Central Angara terrane is distinct from that of adjacent terranes. We study in detail the Yeruda pluton granitoids of the Teya complex, which indicate accretionary-collisional magmatic events in this terrane prior to its collision with Siberia. New geochemistry and SHRIMP U-Th-Pb zircon geochronology of the granites indicate that they formed at 880-860 Ma in a collisional setting. Integrated petromagnetic and paleomagnetic investigations yield a paleomagnetic pole that is significantly different from the corresponding Neoproterozoic interval of the apparent polar wander path (APWP) for Siberia. The difference in paleolatitudes between the Central Angara terrane and the Siberian craton at the time of the Teya granites formation was at least 8.6 degrees, which equals a latitudinal separation of at least 1000 km. We consider various possible positions for the terrane relative to the Siberian craton. These results demonstrate that the 880-860 Ma magmatic events in the Central Angara terrane are not related to events in the western margin of the Siberian craton. Therefore, they do not indicate the existence of a Grenville-age orogenic belt in this location, as proposed by some authors. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.