Timing of closure of the Meso-Tethys Ocean: Constraints from remnants of a 141–135 Ma ocean island within the Bangong–Nujiang Suture Zone, Tibetan Plateau

Abstract Knowledge of the timing closure Meso-Tethys Ocean as represented by Bangong–Nujiang Suture Zone, i.e., Lhasa-Qiangtang collision, is critical for understanding Mesozoic tectonics Tibetan Plateau. But this hotly debated; existing suggestions vary from Middle Jurassic (ca. 166 Ma) to Late Cretaceous 100 Ma). In study, we describe petrology Zhonggang igneous–sedimentary rocks in middle segment Zone and present results zircon U–Pb geochronology, whole-rock geochemistry, Sr–Nd isotope analysis igneous rocks. The have a thick basaltic basement (>2 km thick) covered limestone with interbedded basalt tuff, trachyandesite, chert, poorly sorted conglomerate comprising debris. There an absence terrigenous detritus (e.g., quartz) within sedimentary pyroclastic These observations, together typical exotic blocks-in-matrix structure between surrounding flysch deposits, lead conclusion that are remnants ocean island Ocean. This consistent basalt-type geochemistry basalts trachyandesites, which enriched light rare earth elements (LaN/YbN = 4.72–18.1 5.61–13.7, respectively) positive Nb–Ta anomalies (NbPM/ThPM > 1, TaPM/UPM 1), low initial 87Sr/86Sr ratios (0.703992–0.705428), mantle εNd(t) values (3.88–5.99). Zircon dates indicate formed at 141–135 Ma; therefore, collision Lhasa Qiangtang terranes must happened after ca. 135 Ma.