Abstract: The Dongan gold deposit is located in the northern part of the Lesser Xing’an Range–Zhangguangcai Range metallogenic belt, an important Mo-polymetallic and precious-metal province in Northeast China. The host rocks of the deposit mainly comprise Early Jurassic medium- to coarse-grained alkali-feldspar granite and fine-grained syenogranite, as well as intermediate–felsic volcanic lavas and pyroclastic rocks of the Lower Cretaceous Guanghua Formation. The NE-, nearly N–S- and NNW-trending faults are the principal ore-controlling structures. The hydrothermal mineralization can be divided into three stages: the pyrite–quartz stage (Stage Ⅰ), silicification–adularization–polymetallic sulfide stage (Stage Ⅱ), and chalcedony–fluorite stage (Stage Ⅲ). Fluid inclusions are dominated by aqueous two-phase inclusions. The main mineralization stage is characterized by homogenization temperatures of 154.9~214.5 ℃, salinities of 1.90 %~5.25 %, fluid densities of 0.86~0.94 g/cm³, and estimated mineralization depths of 1.09~1.70 km. These features indicate that the ore-forming fluids were characterized by medium–low temperatures, low salinities and low densities, and that mineralization occurred in a shallow environment. From the early to late mineralization stages, the homogenization temperatures and salinities of the fluids gradually decreased, whereas their densities progressively increased. Laser Raman spectroscopic analyses show that the vapor phase of the fluid inclusions is composed predominantly of H₂O. H–O isotopic compositions indicate that the ore-forming fluids were mixtures of magmatic and meteoric waters, with the latter being dominant, whereas S isotopic compositions suggest that the ore-forming materials were derived from deep-seated magmas. During the late Early Cretaceous, subduction of the Pacific Plate induced lithospheric extension and intensive crust–mantle interaction in the region, resulting in extensive volcanic eruptions. During the waning stage of volcanism, cogenetic magmas were emplaced at shallow crustal levels and exsolved ore-bearing fluids during cooling and crystallization. During their upward migration, the fluids extracted ore-forming materials from the wall rocks and subsequently mixed with meteoric water. The resulting cooling and changes in physicochemical conditions promoted the precipitation and accumulation of ore-forming materials. Therefore, the Dongan gold deposit is a typical low-sulfidation epithermal deposit.