Abstract
The Pia Oắc granite massif is located in Nguyên Bình district, Cao Bang province, which is a part of the Northeast Vietnam-Southwest China granite-related W-Sn matallogenic belt. SIMS U-Pb dating results of zircons from the granite samples show that the granite was emplaced at 93.9±3 Ma. The rocks have initial 87Sr/86Sr ratio of 0.748±0.027, and their eNd(t) ranges from -10.71 to -10.42. Those results suggest that the Pia Oắc granites can be grouped into the Gejiu-Dulong-Dachang granite-related W-Sn belt in Southeast China and relate to Late Mesozoic Yanshan orogeny. The Pia Oắc granite magmas were possibly derived from partial melting of Mesoproterozoic continental crust.