Detrital zircon U–Pb geochronology of the Permian strata in the Turpan–Hami Basin in North Xinjiang, NW China: Depositional age, provenance, and tectonic implications

Abstract

The Permian sedimentary rocks in the Turpan–Hami Basin are key records of the tectonic evolution in the Eastern Tianshan area, although their depositional ages and provenances remain relatively less studied. Here, we conducted detrital zircon U–Pb geochronology on subsurface samples collected from Well LN1 in the Turpan–Hami Basin to understand the depositional ages and provenances of the Permian rocks. In this study, detrital zircon U–Pb ages from the Late Carboniferous Sumuke Formation yielded a notable Permian age population with the youngest single‐grain age at 282.6 Ma. Compiling this result with a published dataset from the surrounding regions of the Turpan–Hami Basin, it shows that the Sumuke Formation was actually deposited in the Early Permian and the Late Carboniferous palynological assemblages within it are of recycled origin. The detrital zircon age spectra of the three Early–Middle Permian samples from Well LN1 define similar unimodal distribution, with prominent late Carboniferous age peaks and scarce Precambrian ages, further indicating that the zircon grains in these three samples should be ultimately sourced from the Jueluotag, the southern branch of the North Tianshan. Regionally, the Bogda, the northern branch of the North Tianshan, as catchment areas recorded interaction between southern and northern sources, and thus, there was a single greater Junggar–Turpan Basin during the Early–Middle Permian. During the latest Middle Permian to Late Permian, provenance shifts occurred at the Jueluotag and the southern piedmont of the Bogda, reflecting the uplift of the Central Tianshan and the Bogda and the isolation of the Junggar Basin and Turpan–Hami Basin. Integrating regional geological studies and provenance evolution trends, we suggest that the Turpan–Hami Basin and its surrounding regions were in a rift setting controlled by post‐collision extension during Early–Middle Permian. By contrast, tectonic contraction and inversion occurred during the latest Middle Permian to Late Permian as a part of the intraplate orogenic process in the Tianshan, which responded to the convergence between the Songpan–Ganzi terrane and palaeo‐Eurasian Plate.