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Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons
Thesis (MSc)--Stellenbosch University, 2025.
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| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613791959646208 |
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| access_status_str | Open Access |
| author | Mangwaya, Langton Tapiwanashe |
| author2 | Von der Heyden, Bjorn |
| author_browse | Mangwaya, Langton Tapiwanashe Von der Heyden, Bjorn |
| author_facet | Von der Heyden, Bjorn Mangwaya, Langton Tapiwanashe |
| author_sort | Mangwaya, Langton Tapiwanashe |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134693 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:46.341Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134693 Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons Mangwaya, Langton Tapiwanashe Von der Heyden, Bjorn Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Gold ores -- Geology -- Africa, Southern Ore deposits -- Africa, Southern Colloidal gold Nanoparticles Geology, Stratigraphic -- Archaean Geology -- Africa, Southern -- Kaapvaal Craton UCTD Thesis (MSc)--Stellenbosch University, 2025. Mangwaya, L. T. 2025. Investigating the Distribution of Colloidal and Nanoparticulate Gold Particles in Archean Orogenic Gold Systems on the Kaapvaal and Zimbabwe Cratons. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/2900d7f5-8110-4218-a846-baa94302e46f ENGLISH ABSTRACT: Gold continues to be a crucial resource used in underpinning global monetary systems, as a repository of wealth, in jewellery, and increasingly in technological applications. The Archean Era is particularly well-endowed in gold mineralisation, which includes structurally hosted orogenic gold in greenstone belts and the supergiant deposits of Witwatersrand Basin. This study seeks to explore the possible relationship between these two geological environments by critically re-appraising the role of the nanoparticulate (<100 nm) and colloidal (< 1 μm) gold size fractions. Towards this end, the study employs a unique combination of non-destructive minerals separation technologies applied to gold mineralised samples from seven orogenic gold deposits located on the Kaapvaal and Zimbabwe cratons. Specifically, SELFRAG was used to disaggregate rocks preferentially along mineral grain boundaries. Individual gold grains were then picked manually in size fractions >125 μm. In sizes fractions < 125 μm gold grains were separated using a novel combination of centrifugation and heavy liquids to isolate the nanoparticulate and colloidal gold grains. This resulted in the identification of 1586 gold grains with sizes ranging from approximately 0.036 μm to 611.66 μm. This empirical dataset was complemented with a thorough collation of published literature on gold grains to better understand gold grain size distributions. 3530 gold grains with sizes ranging from ≈ 1.71 nm to ≈ 1398.59 μm were identified in existing literature. Both datasets were also complemented by size-fractionated sequential cyanide- and aqua regia digest extractions. The evaluations of the resultant gold histograms suggest that gold-grain size distributions decay according to exponential decay curves with exponents ranging between -2.276 and -1.241. Moreover, the colloidal and nanoparticulate grains accounted for between 39% and 46.6% of the total gold grain in these orogenic systems. However, because of their exceedingly small size, they still only represent between approximately 0.00000054% and 0.000054% of the total mass of the gold in the system. From the sequential extraction results, the contribution of small gold increases to 4.24% of the mass by considering all gold in the <25 μm size fraction. Scanning electron microscopy revealed that most of this gold is relatively crystalline, however, a small number of grains showed unique textural features that allude to some diversity in the nucleation and growth of gold during its evolution. The research results indicated that gold colloids and nanoparticles are numerically abundant in Archean orogenic gold systems; however, their contribution to the overall gold endowment is minimal. These findings support the view that colloidal and nanoparticulate gold phases are instrumental in gold preservation and localized particle growth, both of which are key processes contributing to ore formation. The study highlights the quantitative importance of the smallest gold grain size fractions, considering their implications for metallurgical beneficiation, environmental risk, and genetic links between the Witwatersrand gold field and hinterland greenstone-hosted orogenic gold deposits. Overall, it evaluates the contribution of colloidal and nanoparticulate gold to the formation of high-grade Archean orogenic gold deposits, addressing a critical knowledge gap regarding the microscale processes involved in gold mineralization. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-12-23T13:51:48Z 2025-12-23T13:51:48Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134693 en Stellenbosch University xvi, 132 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Gold ores -- Geology -- Africa, Southern Ore deposits -- Africa, Southern Colloidal gold Nanoparticles Geology, Stratigraphic -- Archaean Geology -- Africa, Southern -- Kaapvaal Craton UCTD Mangwaya, Langton Tapiwanashe Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons |
| title | Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons |
| title_full | Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons |
| title_fullStr | Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons |
| title_full_unstemmed | Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons |
| title_short | Investigating the distribution of colloidal and nanoparticulate gold particles in Archean orogenic gold systems on the Kaapvaal and Zimbabwe Cratons |
| title_sort | investigating the distribution of colloidal and nanoparticulate gold particles in archean orogenic gold systems on the kaapvaal and zimbabwe cratons |
| topic | Gold ores -- Geology -- Africa, Southern Ore deposits -- Africa, Southern Colloidal gold Nanoparticles Geology, Stratigraphic -- Archaean Geology -- Africa, Southern -- Kaapvaal Craton UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/134693 |
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