The Xifanping porphyry copper deposit, Yanyuan, is located in the southwestern Yangtze block. LA- ICP- MS zircon U- Pb dating yields an age of 31. 68±0. 28 Ma (MSWD=1. 2; 2σ) for the ore- bearing monzonite porphyry, indicating that it formed in the Oligocene and is consistent to the peaking period of alkali- rich porphyritic magmatism in the region. A.R. value of 3. 59~3. 69, K/N ratio of 0. 89~1. 11, A/NK ratio of 1. 16~1. 24 and A/CNK ratio of 0. 97~1. 13 indicate that the ore- bearing monzonite porphyry are metaluminous- peraluminous and alkaline. The rock is highly enriched in LREE relative to HREE, without distinct Eu anomalies (δEu: 0. 80~0. 85). High Sr and low Yb and Y, and high Sr/Yb and Sr/Y ratios all suggest a typical adakite. The Xifanping adakitic ore- bearing porphyry should be the product of partial melting of delaminated lower crust in a late orogenic setting caused by stress released from the collision of the Indian and Eurasian blocks.