Debate surrounds many of the world’s largest gold deposits as to whether they benefited from multiple episodes of mineralization. The giant Obuasi gold deposit in western Africa is hosted in metasediments affected by a complex deformation history, with at least three structural stages. We used a combination of underground and field mapping, 3D visualization of drill core data, and microstructural studies to investigate the controls on gold mineralization. The majority of the resource is contained between graphite-rich shears, in two distinct styles. These include gold-bearing disseminated arsenopyrite in sedimentary rocks and visible gold within microfractures in quartz veins as much as 4-m-thick. Microstructural observations demonstrate that the arsenopyrite-hosted ore formed coevally with the second stage of cleavage development. In contrast, the underground/field mapping and the 3D visualization of drill core data indicate that the visible gold ore formed coevally with the latest stage of folding and cleavage development. Our results confirm that the Obuasi gold deposit formed during at least two different structural stages. This may indicate that gold was locally remobilized from arsenopyrite into late-stage microfractures, or it may be due to two overprinting and unrelated mineralizing events.
|Number of pages||4|
|Publication status||Published - 2013|