Early Ordovician granites from the South Qiangtang terrane, northern Tibet: Implications for the early Paleozoic tectonic evolution along the Gondwanan proto-Tethyan margin

• Early Ordovician granites emplaced in the South Qiangtang terrane, northern Tibet.
• The granites are S-type and developed in a post-collisional tectonic setting.
• They were mainly derived from anatexis of the Paleoproterozoic metasedimentary rocks.
• Early Paleozoic collisional accretion occurred along the Gondwanan proto-Tethyan margin.

Early Ordovician granites occur in the Gemuri and Bensong Co areas of the South Qiangtang terrane, northern Tibet, and LA-ICP-MS zircon U–Pb dating reveals that the magmatism took place between 486 and 480 Ma. The Geochemical features of these Early Ordovician granites are comparable to those of high-K, calc-alkaline S-type granites. They exhibit negative values of zircon εHf(t) (− 8.5 to + 1.7) and whole-rock εNd(t) (− 8.1 to + 0.5), as well as old zircon Hf model ages (TCDM = 1349–1992 Ma) and whole-rock Nd model ages (TCDM = 1145–1804 Ma). These Early Ordovician granites can be attributed to partial melting of the Paleoproterozoic metasedimentary rocks of the South Qiangtang terrane, while minor amounts of mantle-derived components were introduced into their magma sources. Taking into account previous data, we propose that the Early Ordovician granites developed in a post-collisional tectonic setting and that they were related to the collisional accretion of Asian microcontinental fragments (such as the South China, North China, Tarim, and Qaidam–Kunlun terranes) that took place as a result of oceanic subduction along the Gondwana proto-Tethyan margin during the early Paleozoic.