Gold metallogenesis in craton-margin settings: Insights from orogenic to supergene processes in the Ilesha Schist Belt, SW Nigeria

Abstract

Gold deposits in craton-margin settings represent a distinctive metallogenic environment bridging intracratonic and mobile belt characteristics, yet remain less studied than cratonic and orogenic counterparts. This review examines gold metallogenesis in craton-margin environments using the Ilesha Schist Belt (ISB), a Nigerian Pan-African Belt, as a type example, integrating global analogues to build a framework for deposit genesis and fluid evolution. Four principal deposit types are identified: (1) orogenic lodes, (2) shear-hosted quartz veins, (3) lateritic–residual accumulations, and (4) alluvial–eluvial placers. Craton margins foster unique processes through structural reactivation, hybrid metamorphic–magmatic fluid systems, prolonged weathering that enhances supergene enrichment, and efficient mechanical concentration. A comparative analysis reveals systematic relationships between tectonic setting, deposit style, and fluid character. Key debates include the timing of mineralisation relative to metamorphism, fluid sources (metamorphic, magmatic, and mantle), the role of the cratonic lithosphere in metal endowment, and controls on supergene versus hypogene enrichment. We propose reclassifying the ISB as a hybrid orogenic–supergene system. Additionally, this terrain is recognised as a distinct metallogenic class, requiring specialised exploration approaches. A future research agenda emphases precise geochronology, integrated isotope studies, and quantitative weathering models, offering a refined exploration framework for craton-margin provinces.