The Silurian Tethyan Ocean in central Qiangtang, northern Tibet: Constraints from zircon U-Pb ages of plagiogranites within the Taoxinghu ophiolite

New zircon U-Pb age, Hf isotope, and whole-rock major and trace element data of the Silurian plagiogranites from Taoxinghu ophiolite in central Qiangtang of northern Tibet are reported in this paper. The zircons from plagiogranites have clear oscillatory zones and high Th/U ratios (0.16~0.44), suggesting a magmatic origin. Zircon LA-ICP-MS and Cameca dating of plagiogranites yielded two weighted mean ages of 441Ma±2Ma and 442Ma±3Ma, which are younger than the ages of cumulate gabbros of Taoxinghu ophiolite. The zircons from plagiogranites have positive εHf(t) values (+8.13~+11.23), implying that the plagiogranites were derived from the depleted mantle. Geochemical analysis indicates that the plagiogranites were probably generated by partial melting of cumulate gabbros and their ages were coeval with or slightly younger than oceanic crust generation. The determination of Silurian plagiogranites in Taoxinghu ophiolite reveals the presence of a Silurian Tethyan ocean in central Qiangtang.