Abstract: The geochemical characteristics of the monzonitic granite porphyries in Tiantang copper polymetallic deposit in western Guangdong province，are analyzed.According to the analysis results，contents of SiO₂ are 69.92% ~76.06% with the average value at 74.03%，contents of Al₂O₃ are 12.76%~ 15.34% with the average value at 13.53%，and contents of K₂O are 4.37%~ 7.48% with the average value at 5.64%.The mean values of A/CNK and A/NK are 1.10 and 1.31 respectively.The above geochemical characteristics indicated that the porphyries in Tiantang copper deposit are the peraluminous high-K calcalkaline series of monzonitic granite porphyry that are enriched in silicon and aluminum with high alkalinity.Trace elements of the porphyry in Tiantang Mining area such as Rb，Ba，Sr，average content values of them are 396.36×10-6，343.76×10-6，103.30×10^-6 respectively.Normalized by the trace element of primitive mantle，these porphyries are exhibited enrichment of Rb，K，Th，U and strong loss of Ba，Sr，P，Ti.The average ∑REE value of the porphyries in Tiantang mining area is 245.36×10^-6，the average value of LREE/HREE is 9.87，the average values of δLa/δYb and δEu are 3.50 and 0.28 respectively.Normalized by the REE of chondrite，REE distribution diagrams of the porphyries in Tiantang mining area have the right trend and strong negative Eu anomaly.According to the discrimination diagrams of δRb-δ(Y+Yb)and δRb-δ(Yb+Ta)，the characteristics of these porphyries samples in Tiangtang mining area are identical with that of syn-COLG（collision of granite).It is speculated that，the porphyries in Tiantang mining area are the products of the subsequent evolution of continental collision.

Key words: Tiantang area, Copper deposit, Porphyry, Geochemistry