Abstract: Traditionally, Jiaodong gold deposits are classified into altered-rock type and quartz-vein type. Both are controlled by a unified geodynamic framework, and multiple isotope studies indicate that the ore-forming fluids are broadly homogeneous at regional scale, with both fluids and ore-forming materials showing predominantly deep-source characteristics. However, a convincing explanation for how a single deep hydrothermal system evolves to form two markedly different deposit types remains lacking. In this study, thermodynamic modeling was used to investigate the evolution of ore-forming fluids and gold precipitation mechanisms in both deposit types. Results show that in quartz-vein-type deposits, gold is primarily precipitated by cooling of focused hydrothermal fluids within narrow, open fractures, whereas in altered-rock-type deposits, gold precipitation is mainly driven by sustained water–rock interaction between dispersed vein networks and fractured wall rocks. Simulations further indicate that most pyrite crystallizes earlier than native gold, explaining the common occurrence of native gold in intergranular or intragranular fractures of pyrite and its close association with fine-grained pyrite. Ore-body localization is ultimately controlled by fault geometry governing fluid flow, where gently dipping bend zones and fault intersections with branching structures act as favorable sites for gold deposition due to reduced flow velocity, increased residence time, and enhanced water–rock interaction, while steeply dipping segments mainly serve as fluid conduits, together forming a spatially differentiated “transport–precipitation” system. Based on these results, an end-member metallogenic framework is proposed in which the most strongly mineralized zones correspond to two thermodynamic entropy end-members: quartz-vein-type deposits represent a low-entropy end characterized by highly focused fluid flow, minimal mass exchange, and strong element concentration within narrow fault conduits, whereas altered-rock-type deposits represent a high-entropy end characterized by extensive metasomatism and dispersed ore-forming elements within broad alteration zones. Guided by this concept, multi-source metallogenic indicators (geological, geophysical, and geochemical) can be extracted to construct a system-scale prospectivity model, enabling a transition in mineral exploration from qualitative interpretation to quantitative prediction.