Formation Mechanisms of Lateral Zoning in Orogenic Gold Deposits within Fault Zones: A Case Study of the Xiadian Gold Deposit, Jiaodong Peninsula, China

Abstract The Xiadian orogenic gold deposit, located within the giant Jiaodong Gold Province, is remarkable for hosting three orebody groups with distinct structural, alteration, and mineralization characteristics within the footwall of the Zhao-Ping fault zone. The No. 1 orebody group, containing 75% of the gold resources, is situated within the immediate footwall. The No. 2 and No. 3 orebody groups are located progressively farther from the main fault within the footwall, with correspondingly fewer gold resources. This deposit geometry provides a rare opportunity to investigate the critical factors controlling deposit architecture and mineralization processes. Integrated macroscopic geologic mapping and in situ analysis of pyrite textures, trace elements, and sulfur isotope ratios indicate that each orebody group formed under different structural-hydrodynamic regimes from a single fluid source. The No. 1 orebody group represents a fault core, where quasicontinuous fluid flow under low differential stress formed large tonnage and disseminated ores. The No. 2 orebody group, interpreted as a damage zone, experienced episodic pressure fluctuations and fluid immiscibility, leading to discontinuous gold mineralization and stockwork ores. In contrast, the No. 3 orebody group experienced highly localized, intense fluid pulses through extensional-shear fractures, resulting in higher gold grades but limited resources. This study highlights the importance of coupling macroscopic and microscopic parameters to understand the structural and hydrodynamic factors that control the spatial distribution of gold mineralization in and adjacent to fault zones. This research establishes a predictive model for gold exploration in similar structural settings.