Neoproterozoic-Jurassic Tectonic-Magmatic Events of the Metamorphic Basement in the Nyainrong Microcontinent of Tibet: Implications from Zircon LA-ICP-MS Geochronology

In order to further research the Nyainrong microcontinent and the regional geological conditions of the Tibet Plateau, this paper systematically studied the geochronology of orthogneisses from the Nyainrong microcontinent in Tibet. We obtained the zircon U-Pb ages of nine samples by LA-ICP-MS, which were 502.8±1.2 Ma, 532.7±3.4 Ma, 833.2±2.8 Ma, 734.8±3.3 Ma, 495.3±1.7 Ma, 496.6±2.0 Ma, 495.1±1.2 Ma, 803.8±2.8 Ma, 811.7±2.8 Ma. To analyze these age results, we could divide these ages into three groups: 830-730 Ma, 580-470 Ma, 185-160 Ma. It concludes that the metamorphic basement of Nyainrong microcontinent underwent three tectonic-magmatic events which occurred in the early Neoproterozoic, the late Neoproterozoic to the early Paleozoic, and the early-middle Jurassic. Combined with previous studies, it suggests that the Nyainrong microcontinent has Neoproterozoic basement and occurred the breakup of the Rodinia Supercontinent. The metamorphic basement underwent Pan-African and early Paleozoic tectonic events. Then it underwent early-middle Jurassic magmatic-metamorphic events which were related to the Bangong-Nujiang suture zone subduction and closure.