Studies of orogenic gold deposits have provided abundant information and insight in regards to their age distribution, nature of mineralization and alteration styles as well as structural controls, yet uncertainty remains about certain aspects of the ore-forming hydrothermal processes. Whereas a low-salinity aqueous-carbonic fluid is the preferred mineralizing agent, a unified physicochemical model that explains gold formation remains elusive, despite numerous fluid inclusion studies carried out on orogenic deposits globally. To address the problem, we carried out a multiscale fluid inclusion study of over 30 Archean orogenic deposits from the gold-endowed Abitibi greenstone belt of the Canadian Shield. The research systematically employed a new approach to fluid inclusion investigations which provided the means to obtain physicochemical information beyond what is normally attained by conventional fluid inclusion petrography and microthermometry. Special emphasis was given to: 1) recording and assessing fluid inclusion modification textures and evaluating the related implications (e.g., plastic versus brittle deformation, pressure cycling); 2) constraining the timing of entrapment of fluid inclusion assemblages (FIA) relative to presence of gold; 3) the quantification of fluid chemistry at different stages of the orogenic fluid system (e.g., evaporate mound analysis, in situ LA ICP-MS); and 4) the δ13C isotope signatures of fluid inclusion extracts. The studied deposits cover a wide range of settings in terms of affinity to felsic intrusions, host rock, gold endowment and depth of formation, yet the hydrothermal fluid evolution reconstructed from fluid inclusions is remarkably uniform. Results show that, in general, orogenic hydrothermal systems are long-lived and cover a range of P and T with a significant volume of continuous fluid flow. Early mineralizing fluids have a geochemical signature of Na, As, B, S, K, Cu, W and Sb but are in constant physicochemical evolution due to gradual and/or rapid pressure changes as well as continuous fluid-rock interaction. As a result, the maturing fluid becomes enriched in elements and components sourced from the host rocks, such as Ca, Fe, Mg, K and CO2±CH4. That some of the CO2 and most of the CH4 originates from metasedimentary rocks is inferred from δ13C on fluid extracts which range down to -30‰. At late stages, unmixing often produces a carbonic-rich fluid that is preferentially trapped as the latest FIA associated with the orogenic system. Pyrite-hosted gold mineralization in vein selvages is associated with the early fluid stage, but the timing of precipitation of free gold in quartz veins differ in epizonal versus mesozonal systems. It is broadly coeval with vein formation in the former, but in the latter, including many bonanza-grade ore bodies, it occurs in the late fluid stages and has an affinity to both low pressure regimes and carbonic-rich fluids. The model established in this study is in good agreement with observations from other orogenic gold deposits across geological time and space globally. The study also highlights that some of the fundamental conclusions regarding orogenic gold models acquired using conventional fluid inclusion methods should be reconsidered.