Abstract: Three stages have been recognized for the volcanic activity in the Chibuzhang lake area in northern Xizang on the basis of the K-Ar isotopic age determinations:(1) Stage Ⅰ (40.1-35.1 Ma),during which the volcanic eruption was relatively weak,and only small-scale of fine-grained latite and porphyritic trachyte were formed;(2) Stage Ⅱ (26.5-17.6 Ma),during which the volcanic eruption reached its peak,resulting in the formation of widespread thick-bedded balck vesiculate latite,and Stage Ⅲ (5.5-4.61 Ma),during which the crypto-volcanism permitted the pelletoidal and porphyritic trachyte domes. The Cenozoic volcanic rock series consist of high-potassium calc-alkaline series and shonshonite series. The former ones may be traced back to the Eocene and originated from the crust-derived magmas,whereas the latter ones are of Miocene and Pliocene age,and resulted from the mantle-derived magmas. The rock series record the evolution from the high-potassium calc-alkaline series to shonshonite series,while the lithologies show the evolution from latite to trachyte.