An important spreading event of the Neo-Tethys Ocean during the late Jurassic and early Cretaceous: Evidence from zircon U-Pb SHRIMP dating on diabase in Nagarze, southern Tibet

Widely distributed in Gyangze-Chigu area, southern Tibet, NW- and nearly E-W-trending diabase(gabbro)-gabbro diorite dykes are regarded as the product of the large-scale spreading of the late Neo-Tethys Ocean. In order to constrain the emplacement age of these dykes, zircons of two samples from diabases in Nagarze were dated by using the U-Pb SHRIMP method. Two nearly the same weighted mean Pb-206/U-238 ages were obtained in this paper, which are 134.9 +/- 1.8 Ma (MSWD = 0.65) and 135.5 +/- 2.1 Ma (MSWD = 1.40), respectively. They not only represent the crystallization age of the diabase, but also documented an important spreading event of the Neo-Tethys Ocean during the late Jurassic and early Cretaceous. This dating result is of great significance to reconstruct the temporal framework of the late Neo-Tethys Ocean in the Qinghai-Tibet Plateau.