Abstract: The granite gneiss in the Xinyi area is located on the western margin of the Sulu orogenic belt. This paper discusses its petrogenesis and tectonic environment by examining petrography, rock geochemistry, and zircon U-Pb isotopic chronology of the granite gneiss. It also reveals the repercussions of the breakup event of the Rodinia supercontinent in this area. The findings indicate that the granite gneiss in the study area belongs to the meta-aluminous-weak peraluminous A-type granite, characterized by high SiO2 content, rich alkali, low CaO and Al2O3 contents, and a right-dipping seagull-type rare earth distribution pattern. It is enriched in Rb, Zr, Hf elements, while being severely depleted in Sr, Eu, Nb, Ta elements. The age of the granite gneiss is 746.0-742.5 Ma. The granite gneiss in the Xinyi area originated from the partial melting of lower crustal material and a small amount of mantle-derived material. In the process of magma evolution, it underwent the separation and crystallization of potassium feldspar and plagioclase, and eventually formed through ultra-high pressure metamorphism. The granite gneiss in the Xinyi area was formed in a post-collisional extensional environment in the Neoproterozoic, marking the initial response to the Rodinia supercontinent breakup event in study area of the Sulu orogenic belt.

Key words: Sulu orogenic belt, Xinyi area, Neoproterozoic, granite gneiss, petrogenesis, breakup of the Rodinia supercontinent