Formation and Palaeozoic evolution of the Gorny-Altai-Altai-Mongolia suture zone (South Siberia): Zircon U/Pb constraints on the igneous record

The Altai-Sayan Fold Belt epitomises how Phanerozoic island-arc continental crust contributed to the growth of the Palaeo-Eurasian continent. Its formation is dominated by the closure of the Palaeo-Asian Ocean (PAO) when island-arc systems and Gondwana-derived terranes accreted to the Siberian margin. Relics of the PAO related tectonic units and associated granitoids occur along the ophiolitic Charysh-Terekta-Ulagan-Sayan suture (CTUSs) between Gorny-Altai and Altai-Mongolia. Zircon LA-ICP-MS U/Pb dating of this igneous record constrains the multi-stage geodynamic PAO evolution. Primitive Kuznetsk-Altai island-arc crust formed at the Siberian margin during the Ediacaran-Early Cambrian (525-555 Ma). This island-arc matured during the Middle-Late Cambrian (similar to 510 Ma) and was consumed by PAO subduction in the Late Cambrian-Early Ordovician (480-490 Ma) forming the Siberian Early Caledonian accretion-collision belt. South of the CTUSs, granitic magmatism occurred within Gondwana-derived Altai-Mongolia during the Middle-Late Ordovician (450-470 Ma) Palaeo-Kazakhstan assembly and during a Silurian-Early Devonian (400-425 Ma) Andean-type collision. Middle-Late Devonian (360-395 Ma) granitoids were emplaced as a result of the collision of Altai-Mongolia with Siberia. During final Pangaea amalgamation, the suture was strike-slip reactivated (associated magmatism similar to 295 Ma). The youngest (220-255 Ma) sampled granitoids originated in an intra-plate setting. (C) 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.