Abstract:In order to obtain the age and genesis of quartz diorite-porphyrites of the Deneng copper polymetallic deposit, U-Th-Pb measurement was carried out on zircons from quartz dioriteporphyrites using LA-ICP-MS technique, geochemistry and Sr-Nd-Pb isotopes. Zircon U-Pb dating yielded the ages of 126.6±2.2Ma to 127.5±2.2Ma, which corresponds to the crystallization age of quartz dioriteporphyrites. The quartz dioriteporphyrites belong to the highK calcalkaline series and are characterized by middle SiO2 and high ALK contents. The chondritenormalized REE pattern is right oblique, with (La/Yb)N of 4.64~6.18 and obvious negative Eu anomaly (Eu=0.66~0.74). They are also enriched in large ion lithophile elements (LILEs eg, Rb, Th, K, Pb, Zr and Hf) and depleted in high field strength elements (HFSEs eg, Nb, Ta, P and Ti). The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of quartz dioriteporphyrites vary from 18.629 to 18.77, 15.690 to 15.738 and 39.188 to 39.435, respectively. The (87Sr/86Sr)i varies from 0.709215 to 0.710463,and (143Nd/144Nd)i varies from 0.512044 to 0.512093, with a calculated result of εNd(t) from -8.40 to -7.45 and TDM2from 1524 to 1602 Ma. On the basis of the results above, we can conclude that the quartz dioriteporphyrites should be Itype granite with typical feature of arc magmatism. The genesis can be attributed to the southward subduction of the BangongNujiang Ocean seafloor, which dehydrated and caused the partical melting of mantle wedge. The upwelling of mantle materials led to the partial melting of Mesoproterozoic lower crust and formed the magma of the Deneng quartz dioriteporphyrites.