Gold mineralisation and tectonomagmatic evolution of the Yalgoo-Singleton Greenstone Belt, Western Australia

The Archaean Yalgoo-Singleton greenstone belt (YSGB) represents one of the most understudied supracrustal complexes in the well renowned Yilgarn Craton, Western Australia. Despite being highly prospective for various mineral deposit types and host to several gold deposits, the stratigraphy, structure, geochemistry and ages of rocks in the YSGB remains poorly understood. This study utilises a combination of mapping, petrography, geochemistry, and geochronology to better constrain the development of rocks in the YSGB. Drillcore logging, SEM analysis and stable isotope analysis has determined the style, paragenesis and controls on lode-gold mineralisation in the belt. Detailed mapping shows that the YSGB comprises a lower succession of mafic-ultramafic volcanic rocks, overlain by a sedimentary-dominated succession, and extensively intruded by layered, maficultramafic sills. Geochemical analysis has distinguished multiple distinct volcanic and intrusive subgroups within the stratigraphy, which exhibit geochemical evidence of variable degrees of crustal contamination and fractional crystallisation. U-Pb zircon geochronology has constrained the ages of several previously undated supracrustal units and demonstrates the rapid formation of the greenstone belt over a short interval of < 15 Ma, from ca. 2825-2810 Ma. Coupled geochronology and geochemistry has enabled the correlation of units within the YSGB across the region. This study has established a seven-stage deformational model for rocks in the YSGB, recording a progression from bulk extension that accommodated volcanism, sedimentation, and sill emplacement, to a period of extensive granitic diapirism, followed by bulk horizontal shortening and associated shearing, and successive brittle faulting episodes. Lode-gold deposits in the YSGB are invariably structurally-controlled and were emplaced along steeply-dipping shear zones associated with fluid overpressure, during horizontal shortening. The remarkable consistency of structural style, paragenesis and stable isotope signatures at lode-gold deposits is indicative of a single, widespread mineralising event. The age of lode-gold mineralisation in the belt has been constrained at ca. 2623 Ma.