Lithospheric strike-slip faulting in central Tibet since 35-32 Ma and implications for the incipient Asian extrusional tectonics.

The onset age and depth of the central Tibet strike-slip faults are two still unresolved fundamental issues with regard to the Cenozoic tectonic evolution of central Tibet. Here we present a comprehensive dataset of geochronological, geochemical and structural data on recently discovered en-echelon dykes representing the incipient development of strike-slip faulting from the Lunpola basin in central Tibet. Our results provide evidence for mantle-derived, bimodal magmatism linked to lithospheric-scale strike-slip faulting at 35-32 Ma, and demonstrate that the central Tibet strike-slip faults are at least 20 Ma older than previously estimated (15-8 Ma). We suggest that these faults were originally connected with the lithospheric-scale Jiali and Ailao Shan-Red River shear zones exposed farther east, forming part of a straight, 2500-3000 km-long lithospheric shear zone that favored mantle upwelling and magmatic intrusion coeval with substantial uplift (1.5-2 km) of the central Tibet valley in the early Oligocene.