Thermochronological insights into the structural contact between the Tian Shan and Pamirs, Tajikistan

Multi-method thermochronology along the Vakhsh-Surkhob fault zone reveals the thermotectonic history of the South Tian Shan-Pamirs boundary. Apatite U/Pb analyses yield a consistent age of 251 +/- 2 Ma, corresponding to cooling below similar to 550-350 degrees C, related to the final closure of the Palaeo-Asian Ocean and contemporaneous magmatism in the South Tian Shan. Zircon (U-Th-Sm)/He ages constrain cooling below similar to 180 degrees C to the end of the Triassic (similar to 200 Ma), likely related either to deformation induced by the Qiangtang collision or to the closure of the Rushan Ocean. Apatite fission track thermochronology reveals two low-temperature (<120 degrees C) thermal events at similar to 25 Ma and similar to 10 Ma, which may be correlated with tectonic activity at the distant southern Eurasian margin. The late Miocene cooling is confirmed by apatite (U-Th-Sm)/He data and marks the onset of mountain building within the South Tian Shan that is ongoing today.