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Triassic continental subduction in central Tibet and Mediterranean-style closure of the Paleo-Tethys Ocean

¹ Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
² School of Earth and Environmental Sciences, Washington State University, Pullman, Washington 99164, USA
³ Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100029, China

Correspondence: *E-mail: apullen{at}email.arizona.edu

The Qiangtang metamorphic belt (QMB) in central Tibet is one of the largest and most recently documented high-pressure (HP) to near-ultrahigh-pressure (near-UHP) belts on Earth. Lu-Hf ages of eclogite- and blueschist-facies rocks within the QMB are 244–223 Ma, indistinguishable from the age of UHP metamorphism in the Qinling-Dabie orogen. Results of a U-Pb detrital zircon study suggest that protoliths of the QMB include upper Paleozoic Qiangtang continental margin strata and sandstones that were derived from a Paleozoic arc terrane that developed within the Paleo-Tethys Ocean to the north. We attribute QMB HP metamorphism to continental collision between the Qiangtang terrane and a Paleo-Tethys arc terrane. This collision, and the coeval South China–North China collision, may have slowed convergence between Laurasia and Gondwana-derived terranes and initiated Mediterranean-style rollback and backarc basin development within much of the remnant Paleo-Tethys Ocean realm.

Key Words: Tibet • Qiangtang • eclogite • Paleo-Tethys • continental subduction • rollback