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Steven E. Zhang - One of the best experts on this subject based on the ideXlab platform.
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significance of granite greenstone terranes in the Formation of witwatersrand type gold mineralisation a case study of the neoarchaean black Reef Formation south africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, O.o. Jolayemi, L. Jakaitė, M. Burnett, R J Durrheim, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
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Significance of granite-greenstone terranes in the Formation of Witwatersrand-type gold mineralisation – A case study of the Neoarchaean Black Reef Formation, South Africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, Raymond Durrheim, O.o. Jolayemi, L. Jakaitė, M. Burnett, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
Glen T. Nwaila - One of the best experts on this subject based on the ideXlab platform.
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significance of granite greenstone terranes in the Formation of witwatersrand type gold mineralisation a case study of the neoarchaean black Reef Formation south africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, O.o. Jolayemi, L. Jakaitė, M. Burnett, R J Durrheim, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
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Significance of granite-greenstone terranes in the Formation of Witwatersrand-type gold mineralisation – A case study of the Neoarchaean Black Reef Formation, South Africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, Raymond Durrheim, O.o. Jolayemi, L. Jakaitė, M. Burnett, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
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Recycling of Paleoplacer Gold through Mechanical and Postdepositional Mobilization in the Neoarchean Black Reef Formation, South Africa
The Journal of Geology, 2019Co-Authors: Glen T. Nwaila, M. S. D. Manzi, J. Kirk, H. K. Maselela, Raymond Durrheim, Derek Rose, P. C. Nwaila, L. C. Bam, T. KhumaloAbstract:AbstractThe source of gold in the ca. 2.66 Ga Black Reef Formation (BRF) has been investigated and constrained through petrographic, mineralogical, geochemical, and high-resolution three-dimensiona...
Chuki Hongo - One of the best experts on this subject based on the ideXlab platform.
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assessment to 2100 of the effects of Reef Formation on increased wave heights due to intensified tropical cyclones and sea level rise at ishigaki island okinawa japan
Coastal Engineering Journal, 2021Co-Authors: Chuki Hongo, Masashi KiguchiAbstract:Tropical cyclones (TCs) cause enormous damage to unprotected coastal areas. Healthy coral Reefs can reduce this damage and are low cost and maintenance free. We use a wave simulation model to estim...
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Preliminary identification of key coral species from New Caledonia (Southwest Pacific Ocean), their significance to Reef Formation, and responses to environmental change
Island Arc, 2015Co-Authors: Chuki Hongo, Denis WirrmannAbstract:The recognition of key coral species (KCS) in the geological record, i.e. those that contribute to Reef Formation and maintenance of coral Reef ecosystems, is important for understanding the development and evolution of Reef ecosystems and for forecasting their responses to climate change and anthropogenic impacts in the near future. This study examined the contribution to Reef Formation and maintenance of KCS from Pleistocene and Holocene barrier Reefs in New Caledonia, based on analyses of six cores retrieved from three different Reefs: Islets Kendec, Amedee, and Bayes. Our results indicate that at least 19 genera and 33 species of corals contributed to Reef Formation and maintenance during the Holocene in New Caledonia. Among them, Goniastrea retiformis, Isopora palifera, Dipsastraea pallida/speciosa complex, corymbose Acropora sp., massive Porites sp., and encrusting Porites sp. were KCS during the Holocene. This observation suggests that KCS will potentially contribute to the Formation and persistence of Reefs in the near future under conditions of estimated global sea-level rise of 0.2–0.6 m/100 years. However, the distributions and abundances of these species are currently decreasing. This study emphasizes the need for further research on the restoration and conservation of potential KCS.
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Holocene key coral species in the Northwest Pacific: indicators of Reef Formation and Reef ecosystem responses to global climate change and anthropogenic stresses in the near future
Quaternary Science Reviews, 2012Co-Authors: Chuki HongoAbstract:Abstract The geological record of key coral species that contribute to Reef Formation and maintenance of Reef ecosystems is important for understanding the ecosystem response to global-scale climate change and anthropogenic stresses in the near future. Future responses can be predicted from accumulated data on Holocene Reef species identified in drillcore and from data on raised Reef terraces. The present study analyzes a dataset based on 27 drillcores, raised Reef terraces, and 134 radiocarbon and U–Th ages from Reefs of the Northwest Pacific, with the aim of examining the role of key coral species in Reef growth and maintenance for Reef ecosystem during Holocene sea-level change. The results indicate a latitudinal change in key coral species: arborescent Acropora ( Acropora intermedia and Acropora muricata ) was the dominant Reef builder at Reef crests in the tropics, whereas Porites ( Porites australiensis , Porites lutea , and Porites lobata ) was the dominant contributor to Reef growth in the subtropics between 10,000 and 7000 cal. years BP (when the rate of sea-level rise was 10 m/ka). Acropora digitifera , Acropora hyacinthus , Acropora robusta / A. abrotanoides , Isopora palifera , Favia stelligera , and Goniastrea retiformis from the corymbose and tabular Acropora facies were the main key coral species at Reef crests between 7000 and 5000 cal. years BP (when the rate of sea-level rise was 5 m/ka) and during the following period of stable sea-level. Massive Porites ( P . australiensis , P. lutea , and P. lobata ) contributed to Reef growth in shallow lagoons during the period of stable sea level. Key coral species from the corymbose and tabular Acropora facies have the potential to build Reefs and maintain ecosystems in the near future under a global sea-level rise of 2–6 m/ka, as do key coral species from the arborescent Acropora facies and massive Porites facies, which show vigorous growth and are tolerant to relatively deep-water, low-energy environments. However, these species are likely to experience severe mortality in upcoming decades due to natural and anthropogenic stresses. Consequently, this damage will lead to a collapse in Reef Formation and the maintenance of Reef ecosystems in the near future. This study emphasizes the need for research into the conservation of key coral species.
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key species of hermatypic coral for Reef Formation in the northwest pacific during holocene sea level change
Marine Geology, 2011Co-Authors: Chuki Hongo, Hajime KayanneAbstract:Abstract Cores from Holocene Reefs provided a growth history and species-level identification of corals and demonstrated the most important Reef builders during the Formation stage. This knowledge is important to determine a principle for Reef Formation and to provide preservation plans in the near future. A biological and sedimentological study of sediment cores recovered from the Palau Islands and Yoron Island, northwest Pacific, revealed four major facies: corymbose Acropora, arborescent Acropora, massive Porites, and detritus. Species-level observations show that arborescent Acropora (A. muricata and A. intermedia) contributed to Reef growth under low- to moderate-energy conditions, whereas corymbose and tabular Acropora (A. digitifera, A. hyacinthus, and A. robusta/A. abrotanoides) and I. palifera were key species for Reef Formation under high-energy conditions during Holocene sea-level rise and the ensuing period of sea-level stability. Once sea level had stabilized, massive Porites became restricted to areas subjected to low-energy, turbid conditions. These key species are successful corals because the ecological strategy is rapid growth, determinate growth, a high degree of colony integration, strongly resistant to wave action, and rapid local dispersion via fragmentation. Moreover, the western boundary current (Kuroshio) flows along the Reefs in the northwest Pacific and it is easy for key species to distribute throughout the region during the period of Holocene sea-level rise and stabilization. These features are a principle for Reef Formation during sea-level changes. These key species played a significant role in Holocene Reef Formation in the northwest Pacific; however, coral mortality, caused by climate change, has recently been widely reported. Moreover, the decrease in key species abundance in present-day Reefs has been more severe than that in any other species. These geological findings have important implications regarding the appropriate use of coral transplantation and decisions regarding the optimal location and size of marine protected areas.
M. Burnett - One of the best experts on this subject based on the ideXlab platform.
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significance of granite greenstone terranes in the Formation of witwatersrand type gold mineralisation a case study of the neoarchaean black Reef Formation south africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, O.o. Jolayemi, L. Jakaitė, M. Burnett, R J Durrheim, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
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Significance of granite-greenstone terranes in the Formation of Witwatersrand-type gold mineralisation – A case study of the Neoarchaean Black Reef Formation, South Africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, Raymond Durrheim, O.o. Jolayemi, L. Jakaitė, M. Burnett, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
L. Jakaitė - One of the best experts on this subject based on the ideXlab platform.
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significance of granite greenstone terranes in the Formation of witwatersrand type gold mineralisation a case study of the neoarchaean black Reef Formation south africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, O.o. Jolayemi, L. Jakaitė, M. Burnett, R J Durrheim, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.
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Significance of granite-greenstone terranes in the Formation of Witwatersrand-type gold mineralisation – A case study of the Neoarchaean Black Reef Formation, South Africa
Ore Geology Reviews, 2020Co-Authors: Glen T. Nwaila, H. K. Maselela, Raymond Durrheim, O.o. Jolayemi, L. Jakaitė, M. Burnett, Steven E. ZhangAbstract:Abstract Geological characterisation and U-Pb geochronology of detrital zircon grains has proven valuable in finding potential source terranes of siliciclastic sediments. Sediment transport and reworking from gold-bearing Archaean/Palaeoproterozoic granite-greenstone rocks are significant in the Formation of conglomerate-hosted (Witwatersrand-type) gold deposits. We further support this link with an example from the Neoarchaean Black Reef Formation, in the Carletonville Goldfield, South Africa. In this study, the detrital and hydrothermal pyrite grains are petrographically distinguishable. Association of gold with solely detrital heavy minerals such as pyrite and not with hydrothermal minerals is similar to other Witwatersrand-type examples, which were formed during reducing atmospheric conditions from granite-greenstone protosource rocks. Textural evidence, together with gold occurrence data, support gradual homogenisation of primary sedimentological and mineralogical features due to post-depositional alteration. Uranium-Pb dating of the Black Reef Formation detrital zircon grains yields an age between 3149 and 3061 Ma, indicating that that the provenance of Black Reef Formation sediments could have been derived from a mixture of the hinterland proto granite-greenstone rocks, and from the reworking of Witwatersrand auriferous conglomerates. We further infer a favourable palaeo-drainage for primary sedimentary gold deposition from an isopach model and palaeocurrent data. The fluvial origin of the Black Reef Formation basal conglomerate provides an ideal setting for gold mobilisation from the sediment-source rocks. Notwithstanding the contribution of hydrothermal activity, sedimentary processes are interpreted to have been primary in the initial concentration of gold through reworking of the Witwatersrand auriferous conglomerates. This has important implications for the genesis of the younger Witwatersrand-type gold mineralisation. The fact that the Witwatersrand-type gold deposits, a target for exploration, occur spatially and temporally within the Archaean/Palaeoproterozoic geological record demonstrates that the Witwatersrand Basin is not unique in terms of composition and paragenesis, but is unique in terms of physical size and magnitude of its gold and uranium endowment.