Mesozoic and Cenozoic tectonics of the northern edge of the Tibetan plateau: fission-track constraints

Fission-track analysis on zircons and apatites yields new information about the timing of deformation of the northern Tibetan plateau. Ages on zircons, ranging from 221 +/- 22 to 96 +/- 4 Ma are indicative of a general late Triassic-early Jurassic cooling probably driven by the collision between the Qiantang and Kunlun blocks. Mid-Jurassic slow cooling is recorded also in the apatites in regions not affected by later Cenozoic deformation. This Jurassic denudation was followed by a period of sedimentation during the Cretaceous, except along the Allyn Tagh fault (ATF) zone, and in some restricted areas of the western and eastern Qilian Shan. This long and relatively quiet period ended at about 40 +/- 10 Ma along the major Altyn Tagh and Kunlun strike-slip fault zones, which were activated by the India-Asia collision. This first movement along lithospheric faults resulted in the eastward extrusion of the Tibet plateau, which was followed, in late Oligocene-Miocene times, by a major compression event, initiating the formation of the high relief of north Tibet. A final compressional event took place at 9-5 Ma and is well correlated with high sedimentation rates in the basins of this region. This compression induced continental subduction in the Kunlun ranges, the Altun Shan belt, and possibly the Qilian Shan belt. (C) 2001 Elsevier Science B.V. All rights reserved.