摘要
The Langdu copper deposit is located in the south part of the Indosinian Yidun island arc which is often referred to as the Zhongdian island arc. The Langdu monzonite porphyry occurs in the central and north part of the mine,intruded the Qugasi sandstone and limestone. LA-ICP-MS zircon U-Pb dating yields an age of 223±1 Ma,which is in consistent with the reported Rb-Sr,K-Ar and zircon U-Pb ages of the Late Triassic granitoids in the Zhongdian island arc. It showed they were generated under the same setting. For zircons from the monzonite porphyry,ΣREE values vary mainly in the range of 1168.55 × 10-6～2125. 76×10-6,relatively enriched in HREE.The major and trace element compositions of the monzonite porphyry suggest that the magma was possibly derived from a mixed source of mantle and crustal material due to the western subduction of the Ganzi-Litang ocean plate in Late Triassic. The strong positive Ce anomalies and medium negative Eu anomalies of zircons from the monzonite porphyry showed that the magma had high oxygen fugacity. The temporal-spatial-genetic relationship between the copper mineralization in the Langdu deposit and the monzonite porphyry indicates that high oxygen fugacity was critical for the porphyry-type mineralization.