Abstract The closure of the Paleo‐Tethys Ocean was one of the most important global geological events which formed the framework of the East Asian continent during the early Mesozoic. The Longmu Co‐Shuanghu suture zone is considered to record closure of the main basin of the Paleo‐Tethys Ocean. However, the closure processes remain unclear, which crucially impedes our understanding of the tectonic evolution of the Tethyan oceanic system. In this study, we investigated newly discovered Triassic–Jurassic igneous rocks, including diorite, rhyolite, andesite, and dacite, along the Longmu Co–Shuanghu suture zone. The Middle Triassic diorite (ca. 242 Ma) has a geochemical affinity with andesite and is characterized by high Mg# (53.9–60.9) and variable zircon ε Hf ( t ) (−17.8 to +9.0) and whole‐rocks ε Nd ( t ) (+1.25 to +0.87) values. These features indicate that the diorite was generated by interactions between melts of terrigenous sediment and the mantle in an oceanic subduction setting. Late Triassic rhyolite (ca. 213 Ma) has geochemical characteristics typical of A 2 ‐type granite, with zircon ε Hf ( t ) (−9.7 to +11.6) and whole‐rock ε Nd ( t ) (−0.11 to −0.03) values. The Late Triassic rhyolites, and Early Jurassic andesites ( ε Nd ( t ) = −0.59 to −0.43, ε Nd ( t ) = −10.45 to −9.66) are attributed to partial melting of crustal material, combined with ca. 40%–60% mantle‐derived components introduced into the magma source. In contrast, the Jurassic dacites show limited mantle contribution (ca. 10%–20%). Based on data for igneous rocks from the North Qiangtang area, a Late Triassic continental‐crust thinning event occurred at ca. 218 Ma. This event is roughly coeval with regional tectono‐sedimentary evolution in the north–central Tibetan Plateau. Closure of the Longmu Co–Shuanghu Ocean involved subduction (242–230 Ma), syn‐collision (230–218 Ma), and post‐collision (218–188 Ma) stages. The comparable closure histories of the Longmu Co–Shuanghu and Changning–Menglian Oceans indicate a unified closure history of the Paleo‐Tethys Ocean and further suggest that it may have closed nearly synchronously across East Asia.
Li et al. (Mon,) studied this question.