Precambrian evolution of the Lhasa terrane, Tibet: Constraint from the zircon U–Pb geochronology of the gneisses

Abstract

The Lhasa terrane in south Tibet was traditionally considered as the northern margin of the Gondwana Indian continent. However, the Precambrian tectonic evolution of the Lhasa terrane remains poorly constrained. In this paper, we report zircon geochronology and Ti-in-zircon thermometer for the metamorphic rocks from the eastern segment of the Lhasa terrane. The studied three gneisses underwent the amphibolite-facies and granulite-facies metamorphism. Most zircon grains from two gneisses have a structure of core-mantle-rim. The magmatic cores of the zircon yielded the protolith ages of 1784±25Ma and 1782±31Ma; the overgrowth mantles of the zircon yielded the metamorphic ages of 618±3Ma and 604±69Ma; the metamorphic rims of the zircon from one sample yielded an age of 23.2±0.3Ma. Zircon grains from other gneiss have a structure of core-mantle-rim. The mantles of the zircon yielded a metamorphic age of 1117±29Ma. These data show that the Lhasa terrane witnessed Late Paleoproterozoic magmatism, and three episodes of metamorphism in the Late Mesoproterozoic, Late Neoproterozoic and Cenozoic. This results show that the Lhasa terrane and the Indian continent have similar Precambrian tectonic evolution, which was related to the amalgamation of supercontinents Columbia, Rodinia and Gondwana.