The Subduction Complex in the Yarlung Suture Zone of Southern Tibet: The History of Subduction and the Transition to Continental Collision

Abstract

Subduction complex rocks in the Yarlung suture zone in southern Tibet record the history of oceanic subduction prior to India-Asia collision as well as the entry of the Indian continental margin into the trench. This dissertation presents geological observations and U-Pb detrital zircon data supporting a comprehensive model of subduction accretion and subduction erosion from Triassic to Paleocene time as well as a case study of dust deposition outpacing bedrock erosion in modern catchments within the subduction complex. Major results include documentation of (1) the structural transition from oceanic subduction to continental collision at ca. 59 Ma, (2) a previously unrecognized Jurassic forearc unit, and (3) that the exposed forearc is ~120 Myr younger than the initiation of arc magmatism. Our results suggest that almost the entire pre-Cretaceous forearc was subducted prior to ca. 130 Ma and that an additional intraoceanic subduction zone is not required to explain the units exposed in the Yarlung suture zone.