Abstract:Zhengguang Au deposit is located at the Duobaoshan ore-concentrated area, northern of Great Xing’an Range. In order to constrain petrogenesis of contemporaneous igneous rocks and corresponding metallogenic background, a systematic study on major and trace elemental, geochronology and Hf isotope geochemistry was performed for the dacite porphyry in the Zhengguang Au deposit. Zircon LA-ICP-MS U-Pb dating indicates that dacite porphyry formed in early Ordovician(478~481Ma). Geochemical data shows that the dacite porphyry belongs to metaluminous or peraluminous and high-K calc-alkaline series and is characterized by SiO2≥56%(on average, 63.91%), high alumina contents (Al2O3, on average, 14.85%), low magnesium contents (MgO, average 2.70%), low Y and Yb contents (Y =6.00×10-6 to 7.74×10-6, Yb = 0.70×10-6 to 0.92×10-6), high strontium contents (an average of 368×10-6), high Mg# values, significant fractionation between light REE and heavy REE( (La/Yb) N = 8.74~11.54) , and unobvious Eu anomalies. All of these geochemical features are similar to those of adakites generated by partial melting of a subducted oceanic crust. Furthermore, zircon εHf(t) range from 13.03-13.31 with Hf isotope Two-stage model ages(tDM2) from 605Ma to 624Ma. Both geochemical characteristics and Hf isotope compositions suggest that the dacite porphyry in Zhengguang Au deposit was formed by partial melting of a juvenile subducted oceanic crust. The results of this study also demonstrate that there is a subduction of an oceanic plate, which is located between the Xing’an block and Songnen block, beneath the Xing’an block during the early Ordovician.