Thermal evolution of the metamorphism in the eastern Taiwan Central Range: implications for Yuli Belt exhumation

The Yuli Belt exposed in the eastern part of Taiwan’s Central Range hosts slivers of blueschist-facies meta-igneous rocks that were tectonically emplaced into a mostly greenschist-facies, polyphase deformed metasedimentary succession. Suturing the Eurasian continental plate, the subducted South China Sea plate, the proposed subducted forarc basement, and the Luzon Island arc of the Philippine Sea Plate, the Yuli Belt is a key site for understanding the geodynamic reconstruction of the Taiwan orogeny. In this paper, we reinvestigated the tectonic evolution of the Yuli Belt. The Yuli Belt of the eastern Taiwan Central Range encloses high pressure (HP) mafic–ultramafic blocks and hosts intensely deformed greenschist-facies metasediments. It is still debated if the Chulai Formation to the east is part of the Yuli Belt. To solve this problem, we provide new maximum metamorphic temperature in both units using Raman spectroscopic geo-thermometry in relation to structural deformation. The new peak metamorphic temperatures compiled with published data support systematic spatial variations across the eastern Taiwan Central Range. The Yuli Belt shows peak temperatures of ca. 400°C~550°C higher than those of adjacent units. Temperatures >500°C in the Yuli Belt are close to three HP blocks. The temperature difference between the Yuli Belt and Chulai Formation reaches over 100°C. It is likely that the contact between both units is a fault and that they underwent the same deformation history after its E-vergent backfolding phase. The new peak metamorphic temperatures compiled with published data support systematic spatial variations across the eastern Taiwan Central Range. A revised geological map was generated by the incorporation of new structural data of the metasediments from several river-transects in the eastern Central Range.