Provenance evolution of the Jurassic northern Qaidam Basin (West China) and its geological implications: evidence from detrital zircon geochronology

The Jurassic system is the major hydrocarbon source rock and of crucial importance for understanding the Mesozoic intra-continental tectonics in West China. This paper presents systematic detrital zircon geochronology of the Jurassic outcropping at the Dameigou locality in the northern Qaidam Basin, and reports ~1000 single-grain U-Pb zircon ages that have implications for the provenance, the corresponding basin property as well as the tectonic setting of West China during Jurassic. Zircon ages exhibit two major clusters at ~250 and ~2400 Ma whereas two minor clusters at ~450 and ~850 Ma, suggesting primary sources from the East Kunlun Shan and Oulongbuluke Block, secondary sources from the North Qaidam UHP belt and South Qilian Shan. Combined with observation of lithology and sedimentary facies, two rifting periods were inferred in the earliest Jurassic and the early stage of the Middle Jurassic, respectively, accompanied by further extension throughout the Jurassic. Our results do not support a foreland basin related to the Jurassic southward thrusting of the South Qilian Shan, but favor that the Mesozoic intra-continental tectonics in West China were characterised by pulsed responses to specific collisions rather than a persisting contractional setting during Jurassic period.