Lhasa terrane in southern Tibet came from Australia

The U-Pb age and Hf isotope data on detrital zircons from Paleozoic metasedimentary rocks in the Lhasa terrane (Tibet) define a distinctive age population of ca. 1170 Ma with εHf(t) values identical to the coeval detrital zircons from Western Australia, but those from the western Qiangtang and Tethyan Himalaya terranes define an age population of ca. 950 Ma with a similar εHf(t) range. The ca. 1170 Ma detrital zircons in the Lhasa terrane were most likely derived from the Albany-Fraser belt in southwest Australia, whereas the ca. 950 Ma detrital zircons from both the western Qiangtang and Tethyan Himalaya terranes might have been sourced from the High Himalaya to the south. Such detrital zircon connections enable us to propose that the Lhasa terrane is exotic to the Tibetan Plateau system, and should no longer be considered as part of the Qiangtang-Greater India-Tethyan Himalaya continental margin system in the Paleozoic reconstruction of the Indian plate, as current models show; rather, it should be placed at the northwestern margin of Australia. These results provide new constraints on the paleogeographic reconstruction and tectonic evolution of southern Tibet, and indicate that the Lhasa terrane evolved as part of the late Precambrian-early Paleozoic evolution as part of Australia in a different paleogeographical setting than that of the Qiangtang-Greater India-Tethyan Himalaya system. © 2011 Geological Society of America.