Multistage Remobilization of the Southwestern Margin of the South China Plate: Insights From Zircon U-Pb Geochronology and Hf Isotope of Granitic Rocks From the Yao Shan Complex, Southeastern Tibet Plateau

The Yao Shan complex, located at the southwestern margin of the South China plate, to the east of the Sanjiang-Southeast Asia Tethyan domain, and at the northern extension of the Day Nui Con Voi massif of the Ailao Shan-Red River shear zone, provides a reasonable example to study the multistage tectonic remobilization of continental plates. In this paper, we present new zircon LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) U-Pb dating results and Hf isotopic data of the granitic plutons and dikes from the Yao Shan complex. Zircon U-Pb ages of the granitic intrusions mainly concentrate on three periods: 825-780, 82-69, and 31-29Ma. The zircons are characterized by mainly negative epsilon Hf(t) values with T-DMC ages of 2637-1645, 1964-1610, and 2077-1400Ma, respectively. The results show that the Yao Shan complex record evidences for three episodes of extensive partial melting of middle and lower crustal Precambrian crystalline basement rocks. They contributed to the granitic magmatism in relation to tectonic processes and structural deformation from Neoproterozoic, Late Cretaceous to Oligo-Miocene. Therefore, we argue that the southwestern margin of the South China plate is the weakness for multistage remobilization throughout the tectonic evolution of the plate after its primary cratonization. Remobilization of the plate margin is related to oceanic plate subduction, triggered by rifting in a passive continental margin setting, induced by extension at back-arc setting, or resulted from continental extrusion.