DetritalU–Pbzircon and40Ar/39Armuscovite geochronology of Triassic and Jurassic strata in the southern East Kunlun, northern Tibet Plateau and their geological implications

Abstract

Geochronological dating of detrital minerals from sedimentary rocks can provide invaluable records of the erosional and unroofing history of orogenic systems and link specific sources with their sinks in sedimentary basins. Aiming to establish a better understanding of the thermal and erosional evolution of the East Kunlun Orogenic Belt (E‐KOB), northern Tibet Plateau during the Mesozoic, integrated detrital U–Pb zircon, and40Ar/39Ar muscovite dating was applied to Triassic and Jurassic strata in the southern E‐KOB in this study. Detrital U–Pb zircon ages of clastic rocks from Triassic and Jurassic formations show major age populations at 2,600–2,200 Ma, 2,000–1,700 Ma, 1,000–600 Ma, 530–340 Ma, and 320–220 Ma, while the40Ar/39Ar dating of detrital muscovite yield dominantly Devonian ages with uniform early‐middle Devonian peak ages (380–405 Ma). Our new detrital U–Pb zircon and40Ar/39Ar muscovite ages, combined with the previous palaeocurrent data and comparison with published U–Pb zircon, and40Ar/39Ar muscovite ages of potential source areas, suggest that the E‐KOB was the major source for Triassic and Jurassic strata in the southern East Kunlun. Devonian detrital muscovite40Ar/39Ar ages of the Triassic and Lower Jurassic strata are consistent with the age of syn‐ and post‐collisional magmatic activity in E‐KOB related with the post‐collisional thermal relaxation after closure of the Qimantagh back‐arc basin. The Lower Triassic sedimentary deposits were associated with the subduction of the Kunlun Ocean, which is part of the Palaeo‐Tethys Ocean. The E‐KOB‐derived material in Upper Triassic and Lower Jurassic formations implies that significant surface uplift, unroofing and erosion occurred during the Late Triassic and continued into the Early Jurassic in the East Kunlun region.