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 (~. 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 ~. 295. Ma). The youngest (220-255. Ma) sampled granitoids originated in an intra-plate setting.