Initiation of the Central Tibet Watershed Mountains in Qiangtang: Insights from Provenance Mapping of Detrital Zircon Data Set

The heterogeneous Tibetan lithosphere has led to the formation of distinct geomorphic units on the plateau surface over the past ~250 Myr. One prominent topographical feature is the delineation of intervening sedimentary basins by high mountain belts. Unlike the high and rugged Kunlun, Gangdese and Himalaya Mountains, the Central Tibet Watershed Mountains (CTWM) in the Qiangtang terrane exhibit a relatively low relief of ~1 km or less compared with surrounding basins. They are important geological and geographical barriers with perspectives on the formation process that are subject to dispute. The outburst of detrital zircon geochronology data sets in the Qiangtang basin provides an opportunity to address this issue. The combination of inverse and forward modeling of 6197 detrital zircon U-Pb ages enables the establishment of provenance mapping, which averts tedious descriptions of individual age modes. Integrated with petrographic analysis and paleocurrents, the provenance of the Jurassic Qiangtang basin is quantitatively constrained. The CTWM remained consistently significant sources throughout the Jurassic time. Internal sources of Triassic and Jurassic magmatic rocks locally supplied younger zircon grains. The source proportion of the Hoh Xil- Songpan Ganze (HSG) terrane increased across the basin in the Middle Jurassic but decreased dramatically in the Southern Qiangtang in the Late Jurassic. Contextualized in geological details, an embryonic watershed that separates rivers flowing into the Pacific and Indian oceans formed in central Tibet during the Late Jurassic.