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

Abstract

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 31-29 Ma. The zircons are characterized by mainly negative εHf(t) values with T DMC ages of 2637-1645, 1964-1610, and 2077-1400 Ma, 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.

Migmatite and leucogranite in a continental-scale exhumed strike-slip shear zone: Implications for tectonic evolution and initiation of shearing

“…1). The South China plate is mainly composed of three parts: the Yangtze block to the north, the Cathaysia block to the south, and the Qin-Hang structural belt between them (Chen et al, 2019). Neoproterozoic magmatic rocks, including contemporaneous granitic and mafic rocks, are widely developed along the margins of the South China plate, especially along its northern and western margins (e.g., Qi et al, 2012;Cai et al, 2014Cai et al, , 2015Wang et al, 2016;Li et al, 2018aLi et al, , 2018bChen et al, 2019, Zhou et al, 2020) (Figs.…”

“…During Cenozoic times, the Sanjiang region has undergone sig-nificant crustal thickening, tectonic extrusion, and reorientation of structures triggered by the India-Eurasia collision. Several continentalscale exhumed strike-slip fault zones, such as the Ailao Shan-Red River shear zone (ASRR-SZ), Chongshan shear zone, and Gaoligong shear zone developed in the Sanjiang region (Leloup et al, 2001;Searle et al, 2010;Cao et al, 2011aCao et al, , 2011bCao et al, , 2017Chen et al, 2019;Liu et al, 2020) (Figs. 1 and 2).…”