Abstract
The Dadonggou gold deposit, located in the Liaodong Peninsula of the eastern North China Craton, is a newly recognized giant gold system hosted by Paleoproterozoic phyllite of the Gaixian Formation. In contrast to the common steeply dipping quartz-vein gold deposits in the region, the orebodies at Dadonggou are mainly controlled by subhorizontal to gently dipping structural zones, indicating a distinct structural style of mineralization. To constrain the ore-controlling structures and the associated mineralization mechanism, we integrated structural logging of more than 200 drill holes with field observations, microstructural analysis, and quartz fabric analysis based on electron backscatter diffraction (EBSD).
The deposit records a well-preserved polyphase deformation history. Pre-ore structures in the host rocks include primary bedding (S0), axial planar foliation (S1), crenulation cleavage (S2), and local kink structures (S3), which together defined the inherited structural framework. These fabrics were subsequently overprinted by Jurassic thrust-related deformation, Early Cretaceous low-angle detachment deformation, and late-stage high-angle brittle normal faulting. Structural relationships indicate that the Early Cretaceous detachment event was the principal control on gold mineralization.
Ore-forming fluids were focused upward along regional detachment-related structures during Early Cretaceous extension and then redistributed through a three-dimensional network of low-angle foliations and high-angle fractures within the Gaixian Formation phyllite. Gold precipitation preferentially occurred along mechanically weak and chemically reactive foliation planes, particularly S0, S1, and S2. EBSD quartz fabric data indicate low- to medium-temperature brittle-ductile deformation conditions (∼250–350 °C, locally 300–400 °C), suggesting mineralization near the brittle-ductile transition at depths of ∼ 6–12 km. The Dadonggou deposit is therefore interpreted as a detachment fault-controlled orogenic gold system formed during the Early Cretaceous transition from compression to extension.