Identification of Early Carboniferous Granitoids from Southern Tibet and Implications for Terrane Assembly Related to the Paleo-Tethyan Evolution

This article presents zircon U-Pb and Hf isotope data, together with the whole-rock major-and trace-element composition, of Early Carboniferous granitoids newly identified from the Jiacha and Langxian areas in the southern Lhasa terrane, southern Tibet. The Jiacha rocks are monzogranites that yield zircon U-Pb ages of 347-345 Ma and epsilon(Hf)(t) values from -5.4 to -4.9. The Langxian rocks are granodiorites with slightly older zircon U-Pb ages of 355-352 Ma and lower epsilon(Hf)(t) values from -6.8 to -6.5. Our data suggest that these granitoids were generated largely by reworking of Paleoproterozoic (T-DM(C) = 1.78-1.67 Ga) basement materials. In conjunction with literature data, it is further argued that the southern and central parts of the Lhasa terrane, separated by the Sumdo eclogite belt, should have been an integrated block before the late Paleozoic. Our study supports the notion that the Lhasa terrane was derived from the northern margin of Gondwanaland, in association with formation of at least two stages of Tethyan Ocean basins, now exposed as the Sumdo belt and the Indus-Tsangpo suture.