Abstract:The article mainly foucos on the petrology, geochemistry, zircon chronology and Lu-Hf isotope analysis of the quartz diorite which exposed in Bashikourgan rock group in Munabulake area on the west side of the South Altyn Tagh.Whole Rock geochemical researches indicates that the quartz diorite SiO2 content of 55.94%~57.38%, it exhibits the characteristics of high ratio of Na2O/K2O =1.19~1.60 and quasi-aluminium (A/CNK =0.92~0.95). On the REE partition diagram, all samples show weak or no obvious Eu anomaly, enriched LREE pattern and defected HREE pattern; On the primitive mantle-normalized spider diagram, samples are relatively enriched in large ion lithophile elements (LILE), such as Rb,Th and K, and depleted in high field strength elements (HFSE), such as Nb, Ta, Sr, P and Ti, showing the characteristics of quasi-aluminous I-type granites of crustal high-K calc-alkaline to calc-alkaline series. The zircon crystals in the quartz diorite are euhedral and mostly show long columnar shape with clear oscillatory zones. Zircon U-Pb dating by LA-ICP-MS obtains the age of 455.5±1.3 Ma, which is inferred to represent the formation age of quartz diorite based on the internal structure of CL image of zircon. This age is identical to the high - pressure granulite facies retrograde metamorphic age of HP/UHP rocks from the South Altyn Tagh, and as also identical to the third stage of the magmatism (460~451Ma) in early Paleozoic in South Altyn Tagh. All spots of zircons have εHf(t) =-6.29~-1.35 and TDMC =1512~1823Ma, which is similar to early Paleozoic granite of Southern Altyn Tagh (TDMC =1331~1789Ma, εHf(t) =-8.8~-0.4), suggesting that they were derived from the consistent source rock, which was accreted in Middle Mesoproterozoic -Paleo proterozoic. According to the geochemical characteristics the quartz diorite was inferred to be formed by partial melting of the basalt in the lower crust, and mantle magma should be mixed in the formation process. Combining with the above studies, we indicate that the quartz diorite from Munabulake area in the South Altyn Tagh is produced that metamorphic basalt partially melt and mix with mantle due to the loss of the pressure, then intrude and crystallize into crust in the process of the subduction continental crust turns back.