The Tectonic Responses in the Overriding Plate During the Tethyan Convergence and the Progressive Extrusion Process in Sundaland: Insights From the Wuliangshan Massif, SE Tibetan Plateau

The overriding plate commonly accumulates less strain than the subducted plate during continental collision. Analyzing plate interactions from the perspective of the overriding plate provides important insights into orogenic dynamics. In the southeastern Tibetan Plateau, the Wuliangshan massif, as a key region of the overriding plate, records tectonic events related to the closure of both the Paleo-Tethys and Neo-Tethys. In this study, we present detailed structural analysis, Titanium-in-quartz geothermometry, and zircon U-Pb and Hf isotopic data. These results indicate that the Wuliangshan massif experienced rapid subsidence and deposition within a short period from 260 to 250 Ma in a back-arc tectonic setting. The polyphase deformation events were recognized in the Wuliangshan massif. The ductile syn-metamorphism D₁ event, characterized by a top-to-the-SE ductile shearing under middle-to high-temperature conditions, represents the tectonic response to the collision between the Sibumasu block and the Indochina block occurred at ca. 250–246 Ma. The D₂ deformation is expressed by E-directed thrusts and E-verging folds coeval with a slaty cleavage. The D₃ deformation is marked by SW-directed thrusts and SW-verging folds. The D₂ and D₃ events correspond to positive flower structures related to transpression along the Chongshan-Lancang River fault and the Ailaoshan-Red River fault, respectively. The D₂-related Chongshan-Lancang River fault accommodated the southward extrusion of the western part of Sundaland occurred at 32–27 Ma. The southeastward extrusion of the entire Sundaland was accommodated by the D₃-related Ailaoshan-Red River fault at 27–23 Ma.