Using detrital zircons from late Permian to Triassic sedimentary rocks in the south-eastern Central Asian Orogenic Belt (NE China) to constrain the timing of the final closure of the Paleo-Asian Ocean

Abstract

We present new detrital zircon U–Pb–Hf isotope data for seven samples from late Permian to Triassic sedimentary units in Jilin Province, Northeast (NE) China, and use these data to constrain the timing of final closure of the Paleo-Asian Ocean and the late Permian to Triassic tectonic evolution of the Changchun–Yanji suture belt. The late Permian to Early Triassic sedimentary rocks contain material derived from both the northern margin of the North China Craton and the eastern segment of the Central Asian Orogenic Belt, suggesting that final closure of the Paleo-Asian Ocean occurred during the late Permian at latest. Metamorphic zircons within two metasedimentary units record amphibolite-facies retrograde metamorphism and metamorphic recrystallization events at ∼233Ma, postdating the peak of the collisional event in this area and providing an upper limit for the termination of orogenesis. In comparison, metamorphic zircons with younger ages of ∼223 and ∼210Ma from Middle–Late Triassic sandstones in eastern Jilin Province provide evidence of later hydrothermal events. These results, combined with the presence of voluminous middle Late Triassic terrestrial sedimentary rocks with bidirectional provenances in this area and coeval A-type granites and rhyolites in adjacent areas, suggest that this region underwent post-orogenic extension after the final closure of the Paleo-Asian Ocean. In brief, we suggest that the final closure of the Paleo-Asian Ocean along the Changchun–Yanji belt occurred during the late Permian at latest and that the associated collisional orogeny terminated at ∼233Ma (i.e. early Late Triassic). This belt was subsequently dominated by post-collisional extensional setting during the middle Late Triassic.