Seminar

The South Tianshan Orogenic Belt marks the key site of closure of the southwestern Paleo-Asian Ocean, i.e. the South Tianshan Ocean, and collision of the Tarim Craton with the Central Asian Orogenic Belt. Paleozoic accretionary and collisional tectonics in this region is highly debated, with its significance to Gondwana reconstruction largely overlooked.

This PhD research addresses these issues by tracing the provenance of detrital zircons from Paleozoic-Mesozoic strata in the South Tianshan and northern Tarim regions, and integrating zircon U-Pb-Hf isotopic data with geological records. The results reveal a major tectonic switch from advancing to retreating subduction regimes at ~400 Ma along the southern Paleo-Asian Ocean, leading to the back-arc opening of the South Tianshan Ocean. The South Tianshan oceanic plate was consumed by northward subduction, eventually causing a continental collision at ~315 Ma. The collisional orogeny was probably interrupted and modified by the arrival of the Tarim mantle plume at the end of the Carboniferous. Triassic depositional and tectonothermal events in the western Tianshan represent intracontinental uplifting associated with the far-field effect of the Qiangtang-Tarim collision.

This study shows that switching accretionary events at ~500 Ma and ~400 Ma along the northern margins of the Tarim and
North China cratons can be correlated with the assembly and dispersion of East Gondwana, which provides a new perspectiveof linking the two cratons to the northern Australia margin of Gondwana during Paleozoic time.