The history and mechanism of southeastward extrusion and exhumation of the Tibetan Plateau lithosphere

When and how the plateau lithosphere commenced to expand southeastwards and then induced the fast uplift and exhumation in the SE Tibetan Plateau during the India − Asia collision remain controversial. Here we present zircon U-Pb, mica Ar-Ar, and apatite (U-Th)/He and fission track ages of the granites together with kinematic observations in the Nujiang tectonic zone of the SE Tibetan Plateau. An integrated analysis indicates the earliest pulse of shearing strike slip induced by the southeastward lithospheric expansion in the SE Tibetan Plateau and the establishment of tectonic framework of the SE Tibetan Plateau during 45 − 40 Ma. In addition, the SE Tibetan Plateau, from south to north, had experienced the differential extrusion and uplift during the early Miocene to Pliocene. An integrated analysis suggests that the south and north SE Tibetan Plateau (the boundary line at ca. 26°N) stopped growth at Middle Miocene and Pliocene, respectively. This study provides the most detailed resolution for the southeastward expanding processes of the plateau lithosphere and the exhumation mechanisms of the SE Tibetan Plateau during Cenozoic times to date.