Central Tibetan Meso-Tethyan oceanic plateau

We report the occurrences of the remnants of a Meso-Tethyan oceanic plateau, encompassing an area of ~ 2 × 105 km2 in central Tibet. The plateau remnants include large volumes of pillow basalt formed largely by emergent to subaerial eruption, minor ultramafic intrusives and cumulates, exotic blocks of limestone, radiolarian chert, graywacke, and shale. Isotopic and paleontological dating suggest two major plateau eruptive events at 193–173 Ma and at 128–104 Ma, respectively. The basalts are characterized by enrichment of incompatible elements and a wide range of Sr–Nd isotope composition (initial eNd from –3.71 to + 7.9, initial 87Sr/86Sr from 0.703927 to 0.707618). The trace element and Sr–Nd isotopic data suggest that these basalts are of affinity with those from the Kerguelen and Tethyan plumes, indicative of a plume mantle upwelling origin with involvement of continental material. The wholesale obduction of the Meso-Tethyan oceanic plateau, along with the dismembered normal oceanic crustal fragments, over the Tibetan continental crust could have given rise to perhaps 2 km elevation of central Tibet during the Late Cretaceous.