Original Articles: 2014 Vol: 6 Issue: 3
Differential uplift process in mesozoic-cenozoic Longmen mountains along eastern margin of Tibetan Plateau
Based on analysis on fission track dating of apatite and zircon in the granite and sand samples collected from the south, middle and north segment of Longmen mountain, it is found that the uplift process of Longmen mountain had segmentation on strike and zonation on dip. On dip direction, from Songpan-Ganzi fold belt to Longmen thrust belt and to western Sichuan foreland basin, the entire Songpan-Ganzi fold belt has experienced regional uplift, and the fission track age has positive correlation with altitude; while in Longmen thrust belt, the age has negative correlation with altitude, or is independent of it, which suggests thrust fault play a dominant role during the uplift process. However, in western Sichuan foreland basin, the samples have partly or entirely annealed with burial depth. At both sides of Maoxian-Wenchuan fault, zircon fission track age is obviously different, but for apatite there is no evident difference. This reveals that the west of Maoxian-Wenchuan fault has undergone more rapid uplift during 38-10Ma. At the sides of Beichuan fault, apatite fission track age difference is obvious, suggesting a quick uplift process at the west of Beichuan fault during 10-0Ma. On strike direction, zircon fission track age tends to increase gradually from north to south part of Longmen Mountains, which may indicate a more rapid uplift process during late Indosinian or early Yanshanian in the northern part. Apatite fission track age generally decreases from north to the middle and south, reflecting more rapid uplift in the middle and south in Cenezoic.