Ca. 110 Ma adakite-like magmatism along the Bangong–Nujiang suture zone: Implications for crustal thickening and early uplift in the central Tibetan Plateau

Abstract

The suggested Early Cretaceous timing of early formation of the Tibetan Plateau remains controversial. This study investigates this uncertainty by examining newly identified Early Cretaceous adakite-like magmatic rocks in the Rutog and Nyima areas of the northern–central Tibetan Plateau. Zircon U Pb dating indicates that these rocks formed at ca. 110 Ma and have negative to positive zircon ε Hf (t) values. They contain high concentrations of Sr and have high Sr/Y values, but contain low concentrations of Y and Yb and have low (La/Yb) N , suggesting they have an adakite affinity. They also have ε Nd (t) values that range from −4.5 to +1.3. These geochemical and isotopic data indicate that the adakite-like rocks probably formed from magmas generated by the partial melting of garnet-bearing amphibolite within a thickened region of juvenile and ancient crustal material. This magmatism also most likely occurred during the Lhasa–Qiangtang collisional event. Crustal thicknesses along the Bangong–Nujiang suture zone (BNSZ) were > 40 km in places at ca. 110 Ma, and most likely had a significant impact on the initial uplift of the Tibetan Plateau. In summary, the Early Cretaceous adakite-like magmatic rocks in the Rutog and Nyima areas suggest that the Tibetan Plateau started to form during the Early Cretaceous. • Early Cretaceous adakite-like rocks occur in the north-central Tibet. • Adakite-like rocks were derived from the thickened crust. • The Lhasa–Qiangtang collision happened before ca. 110 Ma. • The significant crustal thickening led to the early uplift in the Early Cretaceous.