Zircons separated from an andesite sample in the Nha Trang formation, in the Khanh Hoa province were dated to determine the protolith age for the complex. Thirty LA-ICP-MS U-Pb zircon analyses gave concordant ages concentrated at 100.9±1.7 Ma, corresponding to the late cretaceous period. These results indicated the protolith age of the ryolite (primary magma crystallization age). The εhf(t) component values ranged from (-)0.6 to (+)10.7, mainly for positive value and only one negative value (-)0.6. It showed that the source of the material forming the andesite eruptions was mainly from mantle, and the continental crust material took part in the formation of the involvement.