Kazisayi monzogranite pluton crops out at the northern margin of the North Altun ophiolitic mélange belt. In this paper, we present petrological, geochemical, and zircon U- Pb and Lu- Hf isotopic data of the Kazisayi monzogranites to constrain their petrogenesis, source and tectonic setting. The Kazisayi monzogranites consist of mainly quartz, alkali feldspar, plagioclase, amphibole and biotite. Zircon U- Pb dating yielded ages of 425~423 Ma. The rocks have high K2O with A/CNK varying from 0. 97 to 1. 07. The granites are weakly peraluminous and and plotted within the medium- K to high- K calc- alkaline fields. These rocks show a negative correlation between P2O5 and SiO2 and show significant features of I- type granite. The REE patterns show a significant depletion in HREE, relative to LREE, and lack Eu anomalies. In the primitive mantle- normalized trace- element diagram, the samples show highly enrichments in Rb, Ba, Th, U and K and depletions in Nb, Ta, P and Ti. The εHf(t) values range from 2. 65~6. 23 with TDM2 (two- stage model ages) from 1015 Ma to 1243 Ma. These characteristics indicate that Kazisayi monzogranites derived mainly from the juvenile crust. Considering the regional tectonic setting, the Kazsayi monzogranites may have formed in a post- collision extensional setting.