Reconstruction of the early-middle Jurassic source-to-sink system in the western Qaidam Basin (North Tibet): Constraints from zircon U-Pb ages of Jurassic sediments and granites

Abstract

• Detrital zircon ages of Jurassic sediments in the western Qaidam Basin show peaks at ∼450 Ma, ∼380 Ma, ∼260 Ma. • The South Qilian Range to the north and South Altyn Tagh Range to the west provided the sources of sediments during the Jurassic. • The Jurassic basin was developed along the southwestern margin of the Paleo-South Qilian Range. • The Jurassic proto-basin in Western Qaidam is reconstructed by provenance analyses. The Qaidam Basin is the largest intermountain basin within the northeastern Tibetan Plateau, which is a key area to understand the tectonic evolution of the Tibetan Plateau. The evolution history and provenances of the western Qaidam Basin were influenced by the surrounding ranges and recorded the history of the topographic changes. To ascertain the relationship between the sediments in the western Qaidam Basin and surrounding source regions is important to understand the tectonic evolution of the Qaidam Basin and the northern Tibetan Plateau. In this study, the 745 detrital zircon LA-ICP-MS U-Pb ages of 14 samples collected from the Heishuigou and Mangya sections were used to trace the provenances of the Jurassic sediments in the western Qaidam Basin and to further constrain the tectonic evolution of the Qaidam Basin in the Meso-Cenozoic. The detrital zircon ages show three age peaks at ∼450 Ma, ∼380 Ma, and ∼260 Ma. Two dated granitoids from the Mangya area have weighted mean ages of 451 ± 3 Ma and 384 ± 3 Ma, respectively. Compared with published zircon U-Pb ages from the relevant basement and magmatic and metamorphic rocks, our results indicate that the South Altyn Tagh Range and the South Qilian Range were main sources of the early-middle Jurassic sediments in the western Qaidam Basin. Together with published stratigraphic, paleocurrent, and seismic profile data, the Jurassic proto-basin was reconstructed. The original Jurassic basin was developed along the southwestern margin of the Paleo-South Qilian Range and displaced sinistrally by the Altyn Tagh Fault during the Cenozoic.