Abstract: The Renwen plagiogranite in Shiquan River area of Tibet consists of oligoclase, quartz, etc. The zircon U-Pb weighted average age measured by LA-ICP-MS is 162.5±2.6Ma. The major elements are characterized by SiO2 content from 72.05% to 72.83%, Al2O3 content from 12.72% to 13.54%, MgO content from 1.19% to 1.24%, Mg# values from 35.73 to 42.27, Na2O content from 4.56% to 4.74%, low K2O content from 0.34% to 0.57%, and Na2O/K2O values from 8.32 to 13.41. The major element geochemistry of Renwen plagiogranite belongs to low potassium calc-alkaline series. Geochemical characteristics of plagiogranite and metabasite suggest that the Renwen plagiogranite may have been derived from partial melting of metabasite, which shows island-arc volcanic characteristics, being enriched in LILE such as Rb, Sr, Ba and depleted in HFSE such as Nb, Ta, Ti. It is concluded that subduction took place in Middle Jurassic in the Shiquanhe suture (the north branch).