The Bada Cu—Au deposit, located in the south of the Yulong metallogenic belt, is a newly discovered collision- type porphyry Cu—Au deposit, which has attracted wide attention of geologists because of its unique intraplate tectonic setting and great prospecting potential. However, the systematic data of the formation of this deposit is very limited and the research degree is still low. In particular, there are few studies on the evolution sequence of alkali- rich volcanic—intrusive rocks and their relationship with Cu—Au mineralization and formation age.Methods: In this paper, we take the alkali- rich volcanic—intrusive complex in Bada Cu—Au deposit as the research object. A total of 25 drilling and fresh outcrop samples were collected, and the whole rock trace analysis were carried out. At the same time, zircon U- Pb geochronology and Sr—Nd—Hf isotopic analysis of tuff, trachyte and fraidronite were also carried out.Results: Trace elements analysis of the whole rock shows that all samples are enriched in large ion lithophile elements (Rb, Sr, Ba) and light rare earth elements (LREE), and depleted in high field strength elements (Nb, Ta, HF) and heavy rare earth elements (HREE), with weak negative Eu anomaly (0.68~0.88). In addition, the weighted average age of n(206Pb)/n(238U) zircons for the tuff, trachyte of the early stsge samples and the fraidronite of the late stage samples are 34.47±0.60 Ma, 34.88±0.59 Ma and 34.18±0.53 Ma, respectively. The results of Sr—Nd—Hf isotopic analysis show that the \[n(87Sr)/n(86Sr)\]i values of the two stage samples range from 0.70629 to 0.70851,εNd(t) values range from -6.41 to -1.57, and εHf(t)values range from 0 to 4.4, the two stage model for Hf was 0.72~1.09 Ga.Conclusions: Based on the detailed field investigation of the alkali- rich volcanic—intrusive complex in the Bada Cu—Au deposit and combined with the results of U- Pb isotope, the complex can be divided into two stages of magmatic events :① during the early stage of Eocene (34.88 to 34.47 Ma), the alkaline volcanic—intrusive rocks erupted and emplaced;②the emplacement of the fraidronite in the late Eocene (34.18 Ma). The characteristics of trace elements and Sr—Nd—Hf isotopes indicate that the complex is mainly derived from the partial melting of enriched mantle metasomatism, and is contaminated by a small amount of crustal material. Based on the above characteristics, it is concluded that the alkali- rich volcanic—intrusive complex in the Bada Cu—Au deposit was formed in the post- collision extensional environment of the Qinghai—Xizang(Tibet) Plateau, and the lithospheric delamination is the key mechanism for its formation.