The Yindonggou deposit, located in the northwestern margin of the Wudang Block, is the largest Ag–Au deposit (reserves: 2000 t Ag and 20 t Au) in the area. Quartz vein- and altered rock-type orebodies are hosted in the meta-volcanic rocks of the Wudang Group, and are controlled by the Yindongyan anticline and ductile shear zone along the anticlinal axis. The metamorphosed quartz keratophyre tuff from the Wudang Group yield LA-ICP-MS zircon concordant 206Pb/238U age of 738.30 ± 5.90 Ma, indicating a Neoproterozoic volcanic event. Four stages of mineralized quartz veins were found in the deposit. One hydrothermal sericite sample collected from the stage 2 smoke-gray quartz Ag–Au veins yield a well-defined 40Ar/39Ar isotopic plateau age of 234.65 ± 3.51 Ma, and 39Ar/36Ar-40Ar/36Ar normal isochron age of 220.11 ± 14.32 Ma, suggesting a Middle to Late Triassic (ca. 234 Ma) mineralization at Yindonggou. The difference between diagenetic and mineralization ages indicates that the Yindonggou deposit is not a volcanic eruption-related deposit, but a vein type epigenetic ore deposit. Five wall-rock samples from the Wudang Group of the Yindonggou deposit yield ISr(234 Ma) ratios of 0.714890–0.723704, averaging 0.719938; the (143Nd/144Nd)i values ranging from 0.512018 to 0.512078, averaging 0.512055, with the εNd(234 Ma) values of −6.22 to −5.05. Galena from stage 1 have ISr(234 Ma) values of 0.710801–0.718999, (143Nd/144Nd)i values of 0.511954–0.512234, and εNd(234 Ma) values of −7.47–2.01. Pyrite and sphalerite from stage 2 yield ISr(234 Ma) ratios of 0.704389–0.719884, (143Nd/144Nd)i values of 0.511920–0.512402 and εNd(234 Ma) values of −8.13 to 1.28. Both εNd(234 Ma) and ISr(234 Ma) values of the sulfides indicate that the ore-forming fluids were contaminated by wall rocks from the Wudang Group. The early stage sulfides are representative of the initial ore-forming fluids, which is similar to metamorphosed basic rocks and Mian-Lue ophiolite. This indicates that the deep-sourced initial ore-forming fluids with high εNd(234 Ma) and low ISr(234 Ma) were derived from the metamorphic devolatilization of the subducted oceanic crust. The Yindonggou is an orogenic-type deposit formed in Triassic oceanic subduction-related accretionary orogeny.