Abstract
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 (ɛHf(t) values ranging from −12.0 to −1.8) indicates a two-stage model age (TDM2) 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 εHf(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.
Highlights
The WNW-trending West Qinling orogen, the western half of the Qinling orogen, is connected to the Kunlun Orogen and the Qaidam terrane in the west [1,2]
Zircon U–Pb dating of diorite in the Zaorendao suggests that the emplacement of diorite occurred at ca. 246.5 Ma, coeval with the widespread Triassic magmatism in the Tongren-Xiahe-Hezuo district (Table 1)
Similar ages were obtained for the Tongren granodiorite (241 Ma [37]; 237 Ma [45]), Shuangpengxi granodiorite (242 Ma [39,46]), Xiekeng diorite–granodiorite (242–244 Ma [39]), Shehaliji quartz monzonite, Granodiorite porphyry and mafic microgranular enclaves (MME) (234 Ma [47]; 234–237 Ma [45]), Ayishan granodiorite (244 Ma [48]; 243–244 Ma [45]), Xiahe granodiorites
Summary
The WNW-trending West Qinling orogen, the western half of the Qinling orogen, is connected to the Kunlun Orogen and the Qaidam terrane in the west [1,2]. The tectonic history evolved in response to subduction and closure of the paleo-Tethys ocean and subsequent continental collision between the South China block and North China block during Late Triassic (Figure 1) [1,2,3,4,5,6] This region contains abundant Cu-Au, Cu-Mo, Au, Au-Sb, and Pb-Zn deposits, and is known to be one of the most. The Tongren-Xiahe-Hezuo district, located to the northwestern section of the West Qinling, contains numerous sediment- and/or dike-hosted disseminated and lode gold deposits, as well as many Cu-Au-W-Fe skarn deposits, and has been one of the most popular districts for exploring metal resources over the last decade (Figure 1) [12,19,22]. U–Pb geochronology, and Lu–Hf isotopic composition of the ore-hosting diorite in the Zaorendao deposit, to: a) establish the time of its emplacement, b) understand the petrogenesis of the diorite
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