S-Type Granites from the Guomang-Co Area in Central Tibet: A Response to Early Paleozoic Andean-Type Orogeny Along the Northern Margin of East Gondwana

The Proto-Tethys Ocean existed between Gondwana and Laurussia during the late Neoproterozoic to Early Paleozoic. As part of the northern margin of East Gondwana, the Lhasa terrane records subduction-related processes of the Proto-Tethys Ocean. This study analyzes mylonitized granites from the Guomang-Co area in the central Lhasa terrane, focusing on their major and trace elements, U-Pb age values, and Sr-Nd-Pb-Hf isotopes. Geochemical and isotopic data consistently indicate S-type affinity derived from Paleoproterozoic metasedimentary sources, and likely formed in a syn-collisional setting. Combined with previous studies, the granites are interpreted as products of the Early Paleozoic Andean-type orogeny along the northern margin of East Gondwana, which indicate southward subduction of the Proto-Tethys Ocean during the Cambrian–Ordovician.