Tectonic uplift since the late Mesozoic and early geomorphological development of the north Qilian Shan on the NE Tibet Plateau: Insights from low–temperature thermochronology

The uplift history of the Qilian Shan and the formation time of modern landforms are key factors in establishing a northward expansion model of the Tibetan Plateau, although previous studies have obtained comprehensive results and an understanding of the areas at both ends of the Qilian Shan. The Gaizhangdaban Shan area, located in the mid–eastern section of the northern Qilian Shan, is characterized by the interplay of granite and Cambrian metamorphic strata, which collectively contribute to the pronounced topographical features in the central part of the Qilian Shan–Hexi Corridor. We employed apatite (U–Th)/He and zircon (U–Th)/He thermochronology, revealing a range of dates predominantly spanning from 300 Ma to 75 Ma. The cooling path model derived from our thermochronological data elucidates two distinct cooling events, dated at ∼78 Ma and ∼15 Ma respectively. Through a comparative analysis of the thermal history across the Qilian Shan range, we proposed that a progressive uplift extending from southern to northern regions commenced in the Late Cretaceous and occurred almost concurrently during the Miocene. We hypothesized that the Late Cretaceous cooling event was influenced primarily by the far–field effects of the collision between the Lhasa and Qiangtang blocks. The subsequent rapid Miocene uplift event is attributed to the closure of the Neo–Tethys Ocean and the consequent outward expansion of the Tibetan Plateau.