Uplift and exhumation in the Tianshan, western China: New insights from detrital zircon morphology and thermochronology

The Tianshan in western China is rich in ore resources, but its tectonic uplift and exhumation history closely related to the resource exploration is still controversial. This study provides a new strategy to uncover the tectonic uplift processes in southern Tianshan by combining the morphological characteristics and thermochronological ages of detrital zircons in the Tarim Basin. The morphology of the Meso-Cenozoic detrital zircons in the Kuqa Foreland Basin, a secondary tectonic unit of the Tarim Basin, is dominated by three types of P, S, and G, and their average alkaline and temperature indexes are 668.0−677.2 and 347.6−413.5, respectively. Moreover, the U-Pb ages of these detrital zircons are primarily divided into two groups of 270−330 and 380−470 Ma. These features indicate that the Early Carboniferous-Early Permian and Middle Ordovician-Middle Devonian alkaline granites distributed in the South Tianshan and southern Central Tianshan were the main sources of the detrital zircons in the Kuqa Foreland Basin. The decomposition of the detrital zircon fission track ages further reveals that the provenances of the Kuqa Foreland Basin primarily consisted of the southern Central Tianshan, the eastern South Tianshan, and the central South Tianshan during Meso-Cenozoic. Among them, the eastern South Tianshan played a dominant role in the material supply. The synthesis of the decomposed zircon fission track (ZFT) ages and the lag-time evolution pattern indicated that the South Tianshan and the southern Central Tianshan mainly experienced five stages of tectonic uplifting that occurred in the Devonian, the Permian, the Middle Triassic-Middle Jurassic, the Cretaceous, and since the Miocene, respectively. They were related to the subduction of the South Tianshan Ocean northward to the bottom of the Central Tianshan, the compression and accretion after the closure of the South Tianshan Ocean, and a series of collisions between the Qiangtang-Lassa-India plates and the southern margin of the Eurasia plate in the Meso-Cenozoic, respectively. This study provides a new provenance analysis method, which was successfully applied in the Tianshan, and also develops a new way to study Central Asia’s tectonic evolution.