Petrogenesis of Ore-Hosting Diorite in the Zaorendao Gold Deposit at the Tongren-Xiahe-Hezuo Polymetallic District, West Qinling, China

• Main Authors: Zong-Yang Gou, Hao-Cheng Yu, Kun-Feng Qiu, Jian-Zhen Geng, Ming-Qian Wu, Yong-Gang Wang, Ming-Hai Yu, Jun Li
• Format: Article
• Language: English
• Published: MDPI AG 2019-01-01
• Series: Minerals
• Subjects: geochronology; Hf isotopes; petrogenesis; paleo-Tethyan ocean closure; Zaorendao gold deposit; West Qinling
• Online Access: https://www.mdpi.com/2075-163X/9/2/76

The newly discovered Zaorendao gold deposit is in the Tongren-Xiahe-Hezuo polymetallic district in the westernmost West Qinling orogenic belt. The estimated pre-mining resource is approximately 13.6 t of Au at an average grade of 3.02 g/t. Mineralization is predominantly controlled by NW-trending and EW-trending faults within diorite intrusions and surrounding sedimentary rocks. In the present study, in situ zircon U⁻Pb geochronology and Lu⁻Hf isotopic analyses of the ore-hosting diorite at Zaorendao were measured using LA-ICP-MS. The data suggest that the diorite was emplaced at ca. 246.5 ± 1.9 Ma. The large variation of zircon Hf isotopic composition (ɛ_Hf(t) values ranging from −12.0 to −1.8) indicates a two-stage model age (T_DM2) that ranges from 1.4 Ga to 2.0 Ga. Such Lu⁻Hf isotopic compositions indicate that the diorite was dominantly derived from a Paleo- to Meso-Proterozoic continental crust. The wide range of ε_Hf(t) and the presence of inherited zircon can be interpreted to suggest the mixing of Paleo- to Meso-Proterozoic continental crust with a mantle component. Combining such characteristics with the geochemistry of coeval rocks that are associated with the diorite, we therefore proposed that the gold-hosting Triassic diorite in the Zaorendao gold deposit formed in an active continental margin that was associated with the northward subduction of the paleo-Tethyan ocean.