The thermo-tectonic history of the Song-Kul plateau, Kyrgyz Tien Shan: Constraints by apatite and titanite thermochronometry and zircon U/Pb dating

The Song-Kul Basin sits on a plateau at the Northern and Middle Kyrgyz Tien Shan junction. It is a lacustrine basin, occupied by lake Song-Kul and predominantly developed on igneous basement. This basement was targeted for a multi-method chronological study to identify the different magmatic episodes responsible for basement formation and to constrain the timing of the development of its present-day morphology. Zircon U/Pb dating by LA-ICP-MS revealed four different magmatic episodes: a Late Cambrian (similar to 500 Ma) island arc system, a Late Ordovician (similar to 450 Ma) subduction related intrusion, an Early Permian (similar to 290 Ma) collisional stage, and a Middle to Late Permian (similar to 260 Ma) post-collisional magmatic pulse. Middle to Late Triassic (similar to 200-230 Ma) titanite fission-track ages and Late Triassic - Early Jurassic (similar to 180-210 Ma) apatite fission-track ages and thermal history modeling indicate the Song-Kul basement was already emplaced in the shallow crust at that time. An exhumed fossil apatite fission-track partial annealing zone is recognized in the bordering Song-Kul mountain ranges. The area experienced only minor post-Early Mesozoic denudation. The igneous basement was slowly brought to apatite (U-Th)/He retention temperatures in the Late Cretaceous-Palaeogene. Miocene to present reactivation of the Tien Shan does not manifestly affect this part of the orogen. (C) 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.