Structural controls on Witwatersrand gold mineralisation

Numerical modelling of structural controls on fluid flow and mineralization

“…Taylor, 1984;De Roo, 1988;Baudemont and Fedorowich, 1996;Broadbent et al, 1998;Yigit et al, 2003;Jolley et al, 2004;Haest et al, 2007), and shown by the examples of vein-type mineralization in this paper. At camp and deposit scales, such structural controls are represented by strain localization (shear strain and dilation), the formation of linear structures (faults, shear zones and fractures) and the reactivation of pre-existing structures, which in turn influence fluid flow and mineral precipitation.…”

“…fault, thrust-fracture or folds) include: (1) the Silvermines PbeZn deposit in Ireland (Taylor, 1984); (2) Mount Carbine WeSn deposit, Queensland, Australia (De Roo, 1988); (3) Dominique-Peter U deposit, Saskatchewan, Canada (Baudemont and Fedorowich, 1996); (4) Century Zn deposit, Northwest Queensland, Australia (Broadbent et al, 1998); (5) Carlin-type Au deposit in the Gold Bar District, Nevada (Yigit et al, 2003). (6) Au deposits in the Witwatersrand basin (Jolley et al, 2004) and Bendigo, Australia (Schaubs and Wilson, 2002); (7) the CueAg deposits of D. R. Congo (Haest et al, 2007). Studying and understanding of key structural factors controlling mineralization in an area can lead to the determination of exploration targets and the discovery of ore bodies (e.g.…”

Hydrothermal alteration in the Witwatersrand goldfields

“…5), the wedging between Lower Wits shale-rich package and the overlying Ventersdorp metabasalt, unconformities, high strain zones in the heterogeneous lithological packages for 1-5 m above unconformities, shear zones (Mullins, 1989) and many small quartz veinlets (Phillips and Law, 2000). Newer data and more detailed interpretations support the model of fluid migration through fracture networks and thrust structures (Jolley et al, 1999(Jolley et al, , 2004, and the additional seismic interpretations confirm a network of structures on the scale of mines and goldfields (Beach and Smith, 2007;Dankert and Hein, 2010). Many of these structures are inferred to have been generated and active during the late Central Rand (Upper Wits) times, and others during post-Klipriviersberg Group-pre Platberg Group thrusting events.…”

“…Detailed small-scale studies show a multitude of deformation and fluid features at the thin section and stope scale (Jolley et al, 2004). At the goldfield and basin scale, studies utilizing seismic surveys (especially with the release of the Anglo American dataset), confirm the interpretations of Coward et al (1995) and greatly extend the basin-wide coverage (Beach and Smith, 2007).…”

Gold-bearing reefs of the Witwatersrand Basin: A model of synsedimentation hydrothermal formation

“…Minerals of the late sulfide assemblage-pyrrhotite, chalcopyrite, sphalerite, and less abundant galena-precipitated from residual solutions along with carbonic matter, gold, and uranium minerals. The localization of especially this mineral assemblage is controlled by tectonic factors, which are deemed to be crucial by advocates of the epigenetic hydrothermal origin of ore-bearing reefs (Jolley et al, 2004). However, the segregation of pyrite as veinlets and zones oriented roughly concordantly to the reef attitude or, less frequently, obliquely or in a fan shape may be explained by petrophysical factors.…”