Geochemical identification of episodes of gold mineralisation in the Barberton Greenstone Belt, South Africa

摘要

The morphology and mineral chemistry of gold and associated sulphides at Sheba, Fairview, and New Consortgold mines in the Barberton Greenstone Belt (BGB) identify two main types of mineralization. The first type occursassociated with sulphides (mainly pyrite), either as inclusions (10–30 μm) or as sub-microscopic gold. Thesecond gold type consists of large gold grains (≥100 μm) within the silicates (mostly quartz).LA-ICP-MS studies reveal that some gold and associated sulphide grains contain high values of Cl, Br, Na, and I.The elemental relationships reflect the different chemistry and precipitation processes of possible source fluids,and identify several episodes of mineralisation in the study area, one of themformed due to a boiling process in asupercritical hydrothermal environment. This paper reports on the compositional characteristics of these goldgrains, the significance of the halogen contents, and the implications for possible sources of the gold and associatedsulphides.