Abstract: Mélange commonly occurs along the collisional boundaries of orogenic belts. Understanding the thermal-age paths of mélange can quantitatively constrain the processes of subduction and arc-continent collision. The Lichi Mélange is distributed along the arc–continent collision boundary between the Northern Luzon Arc and the Taiwan Orogenic Belt. Its origin has long been a matter of debate because of the lack of an objective understanding of the material sources and genetic pathways of the mélange. Therefore, we compared the rare earth element distribution patterns and formation ages of the ophiolite blocks within the Lichi Mélange based on the results of the South China Sea IODP drilling, to specify the material sources of the mélange. Then, using the zircon U-Pb ages of gabbro blocks within the ophiolite, the paleontological data of sedimentary rock involved, the temperatures from clinopyroxene thermometry in gabbro, the homogenization temperatures of inclusions in serpentinized peridotite, and the homogenization temperatures of quartz inclusions in sandstone blocks, we conducted a kinematic coupling analysis of the trench-arc-basin system evolution in consideration of the orogenic events in the Taiwan Orogen and the volcanic activity events in the Northern Luzon Arc. Four key nodes in the thermal-age pathway of the Lichi Mélange were identified at ～17.9 Ma, ～6.2 Ma, ～3.4 Ma, and 1.0 Ma. Finally, we used the genetic pathway of the Lichi Mélange to quantitatively constrain the subduction of the South China Sea oceanic crust beneath the Philippine Sea Plate and its collision with the North Luzon Arc. The Lichi Mélange has a polygenetic origin formed by multi-phased tectonic mixing of forearc basalts, deep-sea flysch deposits, and foredeep basin sediments during the arc-continent collision and reversal uplift, followed by intense shearing and subsequent exposure into the recent position. The thermochronological path of the Lichi Mélange reveals several critical nodes from the initial subduction of the South China Sea oceanic crust, the cryptic initial remote collision of the arc-continent, the exhumation-related near collision of the arc-continent, to the contact collision of the arc-continent. In addition, the genetic pathway quantitatively constrained the subduction-underplating accretion of the South China Sea oceanic crust to the Philippine Sea plate, as well as the arc-continent collision between the Taiwan accretionary wedge and the northern Luzon arc.