Abstract & Overview
New apatite (U-Th)/He from the northeastern \nmargin of the Tibetan Plateau (north \nQilian Shan) indicate rapid cooling began at \n~10 Ma, which is attributed to the onset of \nfaulting and topographic growth. Preservation \nof the paleo-PRZ in the hanging wall and \ngrowth strata in the footwall allow us to calculate \nvertical and horizontal fault slip rates \naveraged over the last 10 Myr of ~0.5 mm/yr \nand ~1 mm/yr respectively, which are within \na factor of two consistent with Holocene slip \nrates and geodetic data. Low fault slip rates \nsince the initiation of the northern Qilian \nShan fault suggest that total horizontal offset \ndid not exceed 10 km. Further, emergence \nof the northern Qilian Shan occurs during \na period of increased aridity in northern \nTibet but is associated with only a minor \nexpansion of the northern plateau perimeter, \nwhich is well established near collision \ntime. Outgrowth of the northern Qilian Shan \nat ~10 Ma could be simple propagation of \nthe larger Qilian Shan system, occurring in \nresponse to decreased slip rates on the Altyn \nTagh fault or as a result of the change in GPE \nof the central plateau.