From mountain range to flat plateau in the Qiangtang Block (western China): Insights from low-temperature thermochronology

The Tibetan Plateau is currently undergoing lateral extrusion and expansion, but it remains unclear whether such orogen-parallel growth occurred during the plateau’s early uplift. Additionally, it is uncertain how this process developed after the formation of the proto-Tibetan Plateau. Constraining both these processes will help improve our understanding of the plateau’s uplift history and mechanisms of formation. This study focuses on the Qiangtang terrane of western China, the core of the proto-Tibetan Plateau, and integrates new low-temperature thermochronological data from Eocene granites with published datasets to reconstruct the uplift history from the perspective of spatiotemporal exhumation patterns. Results reveal that prior to 40−35 Ma, the Qiangtang Plateau experienced not only orogen-perpendicular growth but also east−west-trending expansion. Following establishment of this proto-Tibetan Plateau, localized exhumation persisted in northern Qiangtang. Based on the correlation between apparent exhumation rates and fault activity, geomorphic indices, precipitation, and magmatism, we suggest that compressive thickening was the primary mechanism governing the initial uplift, while crustal channel flow drove the northeastward expansion of the Qiangtang Plateau. Conversely, extensional lithospheric thinning and climate-related erosion processes may have only played a role in localized regions. This study reconstructs the uplift history of the Qiangtang Plateau, from its initial formation as a mountain range to a flat plateau. The findings confirm that lateral growth was likely prevalent during the early stage of uplift and provide thermochronological evidence supporting the topographic transition driven by crustal melting.