This study investigates the petrogenesis of Mesozoic igneous rocks along the Bangong- Nujiang suture zone in Tibet, which is crucial for understanding the tectonic evolution of the Bangong- Nujiang Ocean. We focus on dacites from the Rena- Co area in the southern margin of Qiangtang, using zircon LA- ICP- MS U- Pb dating, Lu- Hf isotopic analysis, and comprehensive geochemical assessments. Our key findings are: ① The Rena- Co dacites were formed approximately 109. 6~109. 5 Ma, as determined by LA- ICP- MS zircon U- Pb dating. ② Geochemically, these rocks display medium- K calc- alkaline affinities with adakite- like characteristics. They exhibit high SiO2 (64. 79%~70. 37%), Al2O3(13. 81%~16. 13%), and Sr (517×10-6~598×10-6), coupled with low Y (8. 45×10-6~10. 7×10-6) and MgO (0. 68%~0. 88%), with Mg# values ranging from 23. 83 to 29. 65 and Sr/Y ratios from 53. 0 to 70. 8. ③ The dacites show strong enrichment in light rare earth elements and large ion lithophile elements (e. g. , Rb, U, Th, K, and Pb), but are depleted in heavy rare earth and high field strength elements (e. g. , Nb, Ta, and Ti), consistent with arc- type magmas generated in subduction zones. ④ Isotopically, they present initial 87Sr/86Sr ratios of 0. 705119~0. 705491, εNd(t) values from 0. 28 to +1. 25, and Nd model ages of 931~806 Ma. Their zircon εHf(t) values range from +3. 9 to +13. 1, indicating a young Hf- depleted mantle age of 924~332 Ma. The combined geochemical and isotopic data suggest the dacites likely originated from juvenile, thickened mafic lower continental crust, potentially incorporating partial melts of metasomatized peridotite and subduction- related fluids. Considering these findings and previous research, we suggest that the closure of the Bangong- Nujiang Ocean occurred post- early Cretaceous.