Geological Characteristics of Iron Oxide-Copper-Gold (IOCG) Type Mineralisation in the Western Bushveld Complex

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dc.contributor.author Hunt, John Paul
dc.date.accessioned 2006-11-15T13:54:49Z
dc.date.available 2006-11-15T13:54:49Z
dc.date.issued 2006-11-15T13:54:49Z
dc.identifier.uri http://hdl.handle.net/10539/1750
dc.description Student Number : 9210081T - MSc dissertation - School of Geosciences - Faculty of Science en
dc.description.abstract The occurrence of large, massive iron oxide deposits throughout the Bushveld Complex, South Africa, and its associated roof-rocks is well known. The style of mineralisation and the associated alteration exhibits many characteristics of iron oxide-copper-gold (IOCG) type deposits. The contained mineralisation is dominated by iron oxide and fluorite and is accompanied by a diverse polymetallic association, with anomalous fluorite, copper, gold, barite, uranium and LREE. The Ruigtepoort orebody, located in the western Bushveld Complex, is such an example and is surrounded by some 20 smaller occurrences in the upper stratigraphic portions of the Bushveld Complex, all displaying strong structural control. These IOCG bodies occur as narrow veins, hydrothermal breccias, subhorizontal sheets, or as pipe-like intrusions usually utilising pre-existing structures. Set in red Nebo granite, the mineralised core consists of severely chloritised rock that is haloed by progressively less-altered granite. The alteration passes from the chlorite core to more hematite-phyllosilicate-dominated alteration, to sericite-illite-dominated alteration; followed by the relatively fresh country granite. These alteration haloes dissipate rapidly away from the body over only a few metres. Sodic-calcic alteration described in other IOCG is not locally observed. Extensive zones of barren feldspar-destructive alteration exist, including K-metasomatism, sericitisation and silicification. Multiple alteration episodes appear to have occurred, resulting in extensive overprinting and a very complex paragenesis. The primary mineral assemblage consists of Fe-chlorite, fluorite, quartz, hematite, and specularite, with accessory pyrite and chalcopyrite. Multiple generations of hematite, quartz, fluorite and chlorite are also observed. At other localities, the assemblage is dominated by magnetite-actinolite-britholite. Significantly enriched concentrations of Au (2 g/t), Cu (0,45 wt%), Ba, Y and LREE are encountered in the small, mineralised core. A fluid mixing model is proposed characterised by an initial highly-saline, sulphur-poor magmatic fluid which mixed with a lower temperature oxidised, surficial fluid. Structure was probably a significant factor in determining the initial distribution of hydrothermal centres and the overall morphology of the entire system. Subsequently, continuous brecciation, alteration, mineral precipitation and fault activity helped develop the hydrothermal centres into a complex array of variably mineralised, lenticular, pipe-like and irregularly shaped breccia bodies. en
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dc.language.iso en en
dc.subject iron oxide-copper-gold en
dc.subject IOCG en
dc.subject Bushveld Complex en
dc.subject Alteration en
dc.subject A-type granite en
dc.subject Vergenoeg en
dc.subject Ruigtepoort en
dc.subject Olympic Dam en
dc.subject Carajas en
dc.title Geological Characteristics of Iron Oxide-Copper-Gold (IOCG) Type Mineralisation in the Western Bushveld Complex en
dc.type Thesis en


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