Precambrian crustal evolution of the southwestern Tarim Craton, NW China: Constraints from new detrital zircon ages and Hf isotopic data of the Neoproterozoic metasedimentary rocks

Abstract

Abstract Neoproterozoic metavolcanic-sedimentary sequences are well preserved along the southwestern margin of Tarim Craton, NW China. In order to constrain the depositional timing of the metasedimentary sequences and better understand the crustal evolution, we present new detrital zircon U–Pb ages and Hf isotopic data for the Neoproterozoic metasediments collected from the eastern Aliankate Group in the southwestern Tarim Craton (STC). The detrital zircons are characterized by high Th/U ratios, clear concentric zoning and euhedral shapes, which imply that the metasediments of the Aliankate Group were mainly derived from a proximal magmatic source. The U–Pb dating of the detrital zircons from three samples shows similar age spectra with an overwhelming population of early to middle Neoproterozoic ages. Zircons from this Neoproterozoic population of the three samples yielded uniform youngest peak age at 790–808\u202fMa, respectively, indicating the maximum depositional age of the eastern Aliankate Group. Based on the published age data of detrital zircons, we suggest that the Aliankate Group most likely deposited at 776–790\u202fMa. Because of the slightly different main age peaks, we also suggest that the Neoproterozoic source materials for the eastern and western of this group may be different although they were both derived from a Neoproterozoic source. The crustal Hf model ages of the Aliankate detrital zircons yield three distinct populations with peaks at 2.13–2.20\u202fGa, ~2.81\u202fGa, and ~3.03\u202fGa, respectively. In combination with the previous published data, we suggest that the southwestern Tarim Craton experienced similar crustal evolution to the northern in the Archean, especially for the earliest three crustal growth events at ~3.6\u202fGa, ~3.0\u202fGa, and ~2.8\u202fGa, but much different since the early Paleoproterozoic. Therefore, we suggest that the southwestern and northern Tarim Craton have uniform Archean basement and likely separated from each other in the early Paleoproterozoic.