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Journal articles on the topic 'Geology, Structural - South Africa - Witwatersrand'

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Published: 4 June 2021

Last updated: 5 February 2022

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1

Beach, Alastair, and Roric Smith. "Structural geometry and development of the Witwatersrand Basin, South Africa." Geological Society, London, Special Publications 272, no. 1 (2007): 533–42. http://dx.doi.org/10.1144/gsl.sp.2007.272.01.27.

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2

Manzi, Musa S. D., Mark A. S. Gibson, Kim A. A. Hein, Nick King, and Raymond J. Durrheim. "Application of 3D seismic techniques to evaluate ore resources in the West Wits Line goldfield and portions of the West Rand goldfield, South Africa." GEOPHYSICS 77, no. 5 (September 1, 2012): WC163—WC171. http://dx.doi.org/10.1190/geo2012-0133.1.

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As expensive as 3D seismic reflection surveys are, their high cost is justified by improved imaging of certain ore horizons in some of the Witwatersrand basin gold mines. The merged historical 3D seismic reflection data acquired for Kloof and South Deep mines forms an integral part of their Ventersdorp Contact Reef mine planning and development programme. The recent advances in 3D seismic technology have motivated the reprocessing and reinterpretation of the old data sets using the latest algorithms, therefore significantly increasing the signal-to-noise ratio of the data. In particular, the prestack time migration technique has provided better stratigraphic and structural imaging in complex faulted areas, such as the Witwatersrand basin, relative to older poststack migration methods. Interpretation tools such as seismic attributes have been used to identify a number of subtle geologic structures that have direct impact on ore resource evaluation. Other improvements include more accurate mapping of the depths, dip, and strike of the key seismic horizons and auriferous reefs, yielding a better understanding of the interrelationship between fault activity and reef distribution, and the relative chronology of tectonic events. The 3D seismic data, when integrated with underground mapping and borehole data, provide better imaging and modeling of critical major fault systems and zones of reef loss. Many faults resolve as multifault segments that bound unmined blocks leading to the discovery and delineation of resources in faulted areas of the mines.

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3

Cairncross, Bruce. "The Witwatersrand Goldfield, South Africa." Rocks & Minerals 96, no. 4 (June 24, 2021): 296–351. http://dx.doi.org/10.1080/00357529.2021.1901207.

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4

Jones, M. Q. W. "Heat flow in the Bushveld Complex, South Africa: implications for upper mantle structure." South African Journal of Geology 120, no. 3 (September 1, 2017): 351–70. http://dx.doi.org/10.25131/gssajg.120.3.351.

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Abstract Geothermal measurements in South Africa since 1939 have resulted in a good coverage of heat flow observations. The Archaean Kaapvaal Craton, in the central part of South Africa, is the best-studied tectonic domain, with nearly 150 heat flow measurements. The greatest density of heat flow sites is in the Witwatersrand Basin goldfields, where geothermal data are essential for determining refrigeration requirements of deep (up to 4 km) gold mines; the average heat flow is 51 ± 6mWm-2. The Bushveld Complex north of the Witwatersrand Basin is an extensive 2.06 Ga ultramafic-felsic intrusive complex that hosts the world’s largest reserves of platinum. The deepest platinum mines reach ~2 km and the need for thermal information for mine refrigeration engineering has led to the generation of a substantial geothermal database. Nearly 1000 thermal conductivity measurements have been made on rocks constituting the Bushveld Complex, and borehole temperature measurements have been made throughout the Complex. The temperature at maximum rock-breaking depth (~2.5 km) is 70°C, approximately 30°C higher than the temperature at equivalent depth in the Witwatersrand Basin; the thermal gradient in the Bushveld Complex is approximately double that in the Witwatersrand Basin. The main reason for this is the low thermal conductivity of rocks overlying platinum mines. The Bushveld data also resulted in 31 new estimates for the heat flux through the Earth’s crust. The overall average value for the Bushveld, 47 ± 7 mW m-2, is the same, to within statistical error, as the Witwatersrand Basin average. The heat flow for platinum mining areas (45 mW m-2) and the heat flux into the floor of the Witwatersrand Basin (43 mW m-2) are typical of Archaean cratons world-wide. The temperature structure of the Kaapvaal lithosphere calculated from the Witwatersrand geothermal data is essentially the same as that derived from thermobarometric studies of Cretaceous kimberlite xenoliths. Both lines of evidence lead to an estimated heat flux of ~17 mW m-2 for the mantle below the Kaapvaal Craton. The estimated thermal thickness of the Kaapvaal lithosphere (235 km) is similar to that defined on the basis of seismic tomography and magnetotelluric studies. The lithosphere below the Bushveld Complex is not significantly hotter than that below the Witwatersrand Basin. This favours a chemical origin rather than a thermal origin for the upper mantle anomaly below the Bushveld Complex that has been identified by seismic tomography studies and magnetotelluric soundings.

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5

Coward, Mike P., Richard M. Spencer, and Camille E. Spencer. "Development of the Witwatersrand Basin, South Africa." Geological Society, London, Special Publications 95, no. 1 (1995): 243–69. http://dx.doi.org/10.1144/gsl.sp.1995.095.01.15.

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6

ENGLAND, G. L., B. RASMUSSEN, B. KRAPEZ, and D. I. GROVES. "Archaean oil migration in the Witwatersrand Basin of South Africa." Journal of the Geological Society 159, no. 2 (March 2002): 189–201. http://dx.doi.org/10.1144/0016-764900-197.

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7

Kershaw, Dave, Bruce Cairncross, Brenda Freese, and Pierre De Vries. "Secondary Minerals from the Carletonville Gold Mines: Witwatersrand Goldfield, South Africa." Rocks & Minerals 78, no. 6 (December 2003): 390–99. http://dx.doi.org/10.1080/00357529.2003.9926753.

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8

Catuneanu, Octavian. "Flexural partitioning of the Late Archaean Witwatersrand foreland system, South Africa." Sedimentary Geology 141-142 (June 2001): 95–112. http://dx.doi.org/10.1016/s0037-0738(01)00070-7.

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9

Humbert, F., A. Hofmann, M. de Kock, A. Agangi, Y.-M. Chou, and P. W. Mambane. "A geochemical study of the Crown Formation and Bird Member lavas of the Mesoarchaean Witwatersrand Supergroup, South Africa." South African Journal of Geology 124, no. 3 (September 1, 2021): 663–84. http://dx.doi.org/10.25131/sajg.124.0022.

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Abstract The ca. 2.97 to 2.80 Ga Witwatersrand Supergroup, South Africa, represents the oldest intracontinental sedimentary basin of the Kaapvaal craton. Two volcanic units occur in this supergroup: the widespread Crown Formation lavas in the marine shale-dominated West Rand Group and the more geographically restricted Bird Member lavas, intercalated with fluvial to fluvio-deltaic sandstone and conglomerate of the Central Rand Group. These units remain poorly studied as they are rarely exposed and generally deeply weathered when cropping out. We report whole-rock major and trace elements, Hf and Nd-isotope whole-rock analyses of the lavas from core samples drilled in the south of the Witwatersrand basin and underground samples from the Evander Goldfield in the northeast. In the studied areas, both the Crown Formation and Bird Member are composed of two units of lava separated by sandstone. Whereas all the Crown Formation samples show a similar geochemical composition, the upper and lower volcanic units of the Bird Member present clear differences. However, the primitive mantle-normalized incompatible trace element concentrations of all Crown Formation and Bird Member samples show variously enriched patterns and marked negative Nb and Ta anomalies relative to Th and La. Despite the convergent geodynamic setting of the Witwatersrand Supergroup suggested by the literature, the Crown Formation and Bird Member are probably not related to subduction-related magmatism but more to decompression melting. Overall, the combined trace element and Sm-Nd isotopic data indicate melts from slightly to moderately depleted sources that were variably contaminated with crustal material. Greater contamination, followed by differentiation in different magma chambers, can explain the difference between the two signatures of the Bird Member. Finally, despite previous proposals for stratigraphically correlating the Witwatersrand Supergroup to the Mozaan Group of the Pongola Supergroup, their volcanic units are overall geochemically distinct.

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10

Howarth, R. J. "A petrologist in South Africa: Frederick Henry Hatch and the Witwatersrand Goldfield." Proceedings of the Geologists' Association 123, no. 1 (January 2012): 189–209. http://dx.doi.org/10.1016/j.pgeola.2011.06.001.

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11

Jolley, S. J., I. H. C. Henderson, A. C. Barnicoat, and N. P. C. Fox. "Thrust-fracture network and hydrothermal gold mineralization: Witwatersrand Basin, South Africa." Geological Society, London, Special Publications 155, no. 1 (1999): 153–65. http://dx.doi.org/10.1144/gsl.sp.1999.155.01.12.

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12

Catuneanu, Octavian, and Mark N. Biddulph. "Sequence stratigraphy of the Vaal Reef facies associations in the Witwatersrand foredeep, South Africa." Sedimentary Geology 141-142 (June 2001): 113–30. http://dx.doi.org/10.1016/s0037-0738(01)00071-9.

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13

Fuchs, Sebastian, Dirk Schumann, Robert F. Martin, and Martin Couillard. "The extensive hydrocarbon-mediated fixation of hydrothermal gold in the Witwatersrand Basin, South Africa." Ore Geology Reviews 138 (November 2021): 104313. http://dx.doi.org/10.1016/j.oregeorev.2021.104313.

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14

Ebert, L. B., E. I. Robbins, K. D. Rose, R. V. Kastrup, J. C. Scanlon, L. A. Gebhard, and A. R. Garcia. "Chemistry and palynology of carbon seams and associated rocks from the Witwatersrand goldfields, South Africa." Ore Geology Reviews 5, no. 5-6 (October 1990): 423–44. http://dx.doi.org/10.1016/0169-1368(90)90045-o.

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15

Gibson, R. L. "40Ar/39Ar constraints on the age of metamorphism in the Witwatersrand Supergroup, Vredefort dome (South Africa)." South African Journal of Geology 103, no. 3-4 (December 1, 2000): 175–90. http://dx.doi.org/10.2113/1030175.

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16

Burron, Ian, Giuliana da Costa, Ryan Sharpe, Mostafa Fayek, Christoph Gauert, and Axel Hofmann. "3.2 Ga detrital uraninite in the Witwatersrand Basin, South Africa: Evidence of a reducing Archean atmosphere." Geology 46, no. 4 (February 2, 2018): 295–98. http://dx.doi.org/10.1130/g39957.1.

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17

Rasmussen, Birger, and Janet R. Muhling. "Reactions destroying detrital monazite in greenschist-facies sandstones from the Witwatersrand basin, South Africa." Chemical Geology 264, no. 1-4 (June 2009): 311–27. http://dx.doi.org/10.1016/j.chemgeo.2009.03.017.

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18

Bowen, Teral B., Julian S. Marsh, Michael P. Bowen, and Hugh V. Eales. "Volcanic rocks of the witwatersrand triad, south Africa. I: Description, classification and geochemical stratigraphy." Precambrian Research 31, no. 4 (June 1986): 297–324. http://dx.doi.org/10.1016/0301-9268(86)90038-0.

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19

Grodner, M. "Delineation of rockburst fractures with ground penetrating radar in the Witwatersrand Basin, South Africa." International Journal of Rock Mechanics and Mining Sciences 38, no. 6 (September 2001): 885–91. http://dx.doi.org/10.1016/s1365-1609(01)00054-5.

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20

Frimmel, Hartwig E. "Chlorite Thermometry in the Witwatersrand Basin: Constraints on the Paleoproterozoic Geotherm in the Kaapvaal Craton, South Africa." Journal of Geology 105, no. 5 (September 1997): 601–16. http://dx.doi.org/10.1086/515962.

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21

England, Gavin L., Birger Rasmussen, Neal J. McNaughton, Ian R. Fletcher, David I. Groves, and Bryan Krapez. "SHRIMP U-Pb ages of diagenetic and hydrothermal xenotime from the Archaean Witwatersrand Supergroup of South Africa." Terra Nova 13, no. 5 (February 11, 2002): 360–67. http://dx.doi.org/10.1046/j.1365-3121.2001.00363.x.

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22

Smieja-Król, Beata, Stanisław Duber, and Jean-Noël Rouzaud. "Multiscale organisation of organic matter associated with gold and uranium minerals in the Witwatersrand basin, South Africa." International Journal of Coal Geology 78, no. 1 (March 2009): 77–88. http://dx.doi.org/10.1016/j.coal.2008.09.007.

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23

JAGUIN, J., P. BOULVAIS, M. POUJOL, M. C. BOIRON, and M. CATHELINEAU. "STABLE ISOTOPE COMPOSITION OF QUARTZ-CALCITE VEINS IN THE WITWATERSRAND BASIN, SOUTH AFRICA: IMPLICATION FOR BASIN-SCALE FLUID CIRCULATION." South African Journal of Geology 113, no. 2 (September 1, 2010): 169–82. http://dx.doi.org/10.2113/gssajg.113.2.169.

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24

Kremenetsky, A. A., and I. E. Maksimyuk. "New data on hydrocarbons in auriferous conglomerates of the Witwatersrand ore region, Republic of South Africa." Lithology and Mineral Resources 41, no. 2 (March 2006): 102–16. http://dx.doi.org/10.1134/s0024490206020027.

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25

ELS, B. G. "Anomalous pebble size variation in an erosive, Late Archaean braided stream: the Middelvlei gold placer, Witwatersrand, South Africa." Sedimentology 40, no. 1 (February 1993): 41–52. http://dx.doi.org/10.1111/j.1365-3091.1993.tb01089.x.

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26

Duane, M. J., G. Pigozzi, and C. Harris. "Geochemistry of some deep gold mine waters from the western portion of the Witwatersrand Basin, South Africa." Journal of African Earth Sciences 24, no. 1-2 (January 1997): 105–23. http://dx.doi.org/10.1016/s0899-5362(97)00030-4.

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27

Gibson, R. L., and M. Q. W. Jones. "Late Archaean to Palaeoproterozoic geotherms in the Kaapvaal craton, South Africa: constraints on the thermal evolution of the Witwatersrand Basin." Basin Research 14, no. 2 (June 2002): 169–81. http://dx.doi.org/10.1046/j.1365-2117.2002.00168.x.

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28

Kositcin, Natalie, and Bryan Krapež. "Relationship between detrital zircon age-spectra and the tectonic evolution of the Late Archaean Witwatersrand Basin, South Africa." Precambrian Research 129, no. 1-2 (February 2004): 141–68. http://dx.doi.org/10.1016/j.precamres.2003.10.011.

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29

Gibson, R. L., and W. U. Reimold. "The significance of the Vredefort Dome for the thermal and structural evolution of the Witwatersrand Basin, South Africa." Mineralogy and Petrology 66, no. 1-3 (1999): 5–23. http://dx.doi.org/10.1007/bf01161720.

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30

Marsh, J. S., M. P. Bowen, N. W. Rogers, and T. B. Bowen. "Volcanic rocks of the Witwatersrand Triad, South Africa. II: Petrogenesis of mafic and felsic rocks of the Dominion Group." Precambrian Research 44, no. 1 (July 1989): 39–65. http://dx.doi.org/10.1016/0301-9268(89)90075-2.

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31

Fuchs, Sebastian, Anthony E. Williams-Jones, Simon E. Jackson, and Wojciech J. Przybylowicz. "Metal distribution in pyrobitumen of the Carbon Leader Reef, Witwatersrand Supergroup, South Africa: Evidence for liquid hydrocarbon ore fluids." Chemical Geology 426 (May 2016): 45–59. http://dx.doi.org/10.1016/j.chemgeo.2016.02.001.

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32

Pham, Luan Thanh. "A high resolution edge detector for interpreting potential field data: A case study from the Witwatersrand basin, South Africa." Journal of African Earth Sciences 178 (June 2021): 104190. http://dx.doi.org/10.1016/j.jafrearsci.2021.104190.

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33

Fuchs, Sebastian H. J., Dirk Schumann, Anthony E. Williams-Jones, Andrew J. Murray, Martin Couillard, Ken Lagarec, Michael W. Phaneuf, and Hojatollah Vali. "Gold and uranium concentration by interaction of immiscible fluids (hydrothermal and hydrocarbon) in the Carbon Leader Reef, Witwatersrand Supergroup, South Africa." Precambrian Research 293 (May 2017): 39–55. http://dx.doi.org/10.1016/j.precamres.2017.03.007.

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34

Jolley, S. J., G. W. Stuart, S. R. Freeman, R. J. Knipe, D. Kershaw, E. McAllister, A. C. Barnicoat, and R. F. Tucker. "Progressive evolution of a late orogenic thrust system, from duplex development to extensional reactivation and disruption: Witwatersrand Basin, South Africa." Geological Society, London, Special Publications 272, no. 1 (2007): 543–69. http://dx.doi.org/10.1144/gsl.sp.2007.272.01.28.

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35

Nwaila, G. T., R. J. Durrheim, O. O. Jolayemi, H. K. Maselela, L. Jakaitė, M. Burnett, and S. E. Zhang. "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 121 (June 2020): 103572. http://dx.doi.org/10.1016/j.oregeorev.2020.103572.

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36

Noffke, Nora, Nic Beukes, Jens Gutzmer, and Robert Hazen. "Spatial and temporal distribution of microbially induced sedimentary structures: A case study from siliciclastic storm deposits of the 2.9Ga Witwatersrand Supergroup, South Africa." Precambrian Research 146, no. 1-2 (April 2006): 35–44. http://dx.doi.org/10.1016/j.precamres.2006.01.003.

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37

Pienaar, D., B. M. Guy, C. Pienaar, and K. S. Viljoen. "A geometallurgical characterization study of the Crystalkop Reef at the Great Noligwa Mine, Klerksdorp Goldfield, South Africa." South African Journal of Geology 120, no. 3 (September 1, 2017): 303–22. http://dx.doi.org/10.25131/gssajg.120.3.303.

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Abstract Mineralogical and textural variability of ores from different sources commonly leads to processing inefficiencies, particularly when a processing plant is designed to treat ore from a single source (i.e. ore of a relatively uniform composition). The bulk of the Witwatersrand ore in the Klerksdorp goldfield, processed at the AngloGold Ashanti Great Noligwa treatment plant, is derived from the Vaal Reef (>90%), with a comparatively small contribution obtained from the Crystalkop Reef (or C-Reef). Despite the uneven contribution, it is of critical importance to ensure that the processing parameters are optimized for the treatment of both the Vaal and C-Reefs. This paper serves to document the results of a geometallurgical study of the C-Reef at the Great Noligwa gold mine in the Klerksdorp goldfield of South Africa, with the primary aim of assessing the suitability of the processing parameters that are in use at the Great Noligwa plant. The paper also draws comparisons between the C-Reef and the Vaal Reef A-facies (Vaal Reef) and attempts to explain minor differences in the recovery of gold and uranium from these two sources. Three samples of the C-Reef were collected in-situ from the underground operations at Great Noligwa mine for mineralogical analyses and metallurgical tests. Laboratory-scale leach tests for gold (cyanide) and uranium (sulphuric acid) were carried out using dissolution conditions similar to that in use at the Great Noligwa plant, followed by further diagnostic leaching in the case of gold. The gold in the ore was found to be readily leachable with recoveries ranging from 95% to 97% (as opposed to 89% to 93% for the Vaal Reef). Additional recoveries were achieved in the presence of excess cyanide (96% to 98%). The recovery of uranium varied between 72% and 76% (as opposed to 30% to 64% for the Vaal Reef), which is substantially higher than predicted, given the amount of brannerite in the ore, which is generally regarded as refractory. Thus, the higher uranium recoveries from the C-Reef imply that a proportion of the uranium was recovered by the partial dissolution of brannerite. As the Vaal Reef contain high amounts of chlorite (3% to 8%), which is an important acid consumer, it is considered likely that this could have reduced the effectiveness of the H2SO4 leach in the case of the ore of the Vaal Reef. Since the gold and uranium recoveries from the C-Reef were higher than the recoveries from the Vaal Reef, the results demonstrate that the processing parameters used for treatment of the Vaal Reef are equally suited to the treatment of the C-Reef. Moreover, small processing modifications, such as increased milling and leach retention times, may well increase the recovery of gold (particularly when e.g. coarse gold, or unexposed gold, is present).

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38

REIMOLD, W. U. "COMMENT ON "PSEUDOTACHYLITE IN THE SOUTH BOUNDARY FAULT AT THE COOKE SHAFT, WITWATERSRAND BASIN, SOUTH AFRICA BY P.W. MAMBANE ET AL., SOUTH AFRICAN JOURNAL OF GEOLOGY 114.2, 109-120." South African Journal of Geology 115, no. 2 (June 1, 2012): 251–55. http://dx.doi.org/10.2113/gssajg.115.2.251.

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39

Rasmussen, Birger, Ian R. Fletcher, Janet R. Muhling, Andreas G. Mueller, and Greg C. Hall. "Bushveld-aged fluid flow, peak metamorphism, and gold mobilization in the Witwatersrand basin, South Africa: Constraints from in situ SHRIMP U-Pb dating of monazite and xenotime." Geology 35, no. 10 (2007): 931. http://dx.doi.org/10.1130/g23588a.1.

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40

Hayward, C. L., W. U. Reimold, R. L. Gibson, and L. J. Robb. "Gold mineralization within the Witwatersrand Basin, South Africa: evidence for a modified placer origin, and the role of the Vredefort impact event." Geological Society, London, Special Publications 248, no. 1 (2005): 31–58. http://dx.doi.org/10.1144/gsl.sp.2005.248.01.02.

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41

McCourt, Stephen, and Dirk van Reenen. "Structural geology and tectonic setting of the Sutherland Greenstone Belt, Kaapvaal Craton, South Africa." Precambrian Research 55, no. 1-4 (March 1992): 93–110. http://dx.doi.org/10.1016/0301-9268(92)90017-i.

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42

Smit, C. A., C. Roering, and D. D. van Reenen. "The structural framework of the southern margin of the Limpopo Belt, South Africa." Precambrian Research 55, no. 1-4 (March 1992): 51–67. http://dx.doi.org/10.1016/0301-9268(92)90014-f.

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43

Karpeta, W. P. "Sedimentology and gravel bar morphology in an Archaean braided river sequence: the Witpan Conglomerate Member (Witwatersrand Supergroup) in the Welkom Goldfield, South Africa." Geological Society, London, Special Publications 75, no. 1 (1993): 369–88. http://dx.doi.org/10.1144/gsl.sp.1993.075.01.21.

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44

Pretorius, C. C., W. F. Trewick, A. Fourie, and C. Irons. "Application of 3-D seismics to mine planning at Vaal Reefs gold mine, number 10 shaft, Republic of South Africa." GEOPHYSICS 65, no. 6 (November 2000): 1862–70. http://dx.doi.org/10.1190/1.1444870.

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During 1994, a 3-D seismic reflection survey was undertaken at Vaal Reefs No. 10 shaft with the objective of mapping the detailed structure of the Ventersdorp contact reef gold orebody. This would provide vital input into future mine planning and development. The survey benefitted from 10 years of 2-D seismic experience and one previous 3-D mine survey, conducted in the Witwatersrand Basin. The seismic survey at No. 10 shaft accurately and spectacularly delineated the 3-D structure of the Ventersdorp contact reef at depths ranging from 1000 to 3500 m, imaging faults with throws in the 20- to 1200-m range. The resultant structure plans were satisfactorily validated by subsequent surface drilling and underground mapping mining operations during the period 1994 to 1996. These plans have been merged with drillhole, underground, and sampling data into an integrated mine modeling, gold reserve estimation, and mine scheduling package. The geology department now manages the planning function at No. 10 shaft, and 3-D seismics has played a significant role in placing this important responsibility firmly within the geologists’ domain. Building on the success of the No. 10 shaft survey, two other 3-D seismic surveys were concluded over mines during 1996 and 1997.

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45

Basson, I. J. "Structural overview of selected Group II kimberlite dyke arrays in South Africa: implications for kimberlite emplacement mechanisms." South African Journal of Geology 106, no. 4 (December 1, 2003): 375–94. http://dx.doi.org/10.2113/106.4.375.

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46

Mkhatshwa, S. F., B. M. Guy, A. J. B. Smith, and K. S. Viljoen. "A mineralogical perspective on the recovery of uranium from brannerite-rich ore at Cooke Section, West Rand Goldfield, South Africa." South African Journal of Geology 123, no. 4 (November 9, 2020): 615–32. http://dx.doi.org/10.25131/sajg.123.0031.

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Abstract The recovery of uranium from quartz-pebble conglomerates of the Witwatersrand Basin is accomplished through sulphuric acid dissolution under oxidising conditions. At Cooke Section on the West Rand Goldfield, the extraction process has been plagued by low to moderate yields on the order of 40 to 75%, as opposed to a target recovery of 80%. This has been ascribed to the high abundance of brannerite in the ore, which has traditionally been more problematic to leach. In addition to brannerite, poor metallurgical recoveries may also be associated with processing inefficiencies related to comminution, residence time, acid dosage and leach temperature. In view of this, a range of ore samples (channel samples) were collected from four uranium-bearing conglomerate horizons at Cooke Section (the A1, A5, E9EC and UE1A reefs) for detailed mineralogical and metallurgical characterisation, involving automated mineralogical analysis, and laboratory-scale leach testwork. The mineralogical results show that the major uranium-bearing minerals of uraninite, coffinite and brannerite are fine-grained (~80% passing 32 micron) and exhibit high degrees of mineral exposure to the lixiviant (~99%). Despite these favourable attributes, the elemental deportment data indicate that brannerite accounts for approximately 43% of the combined uranium budget. Further inspection shows that brannerite can be subdivided into three compositional subtypes: uraniferous brannerite (~13% U deportment), brannerite (~25% U deportment) and titaniferous brannerite (~5% U deportment). Baseline laboratory leach tests, which replicated plant leach conditions of 30 kg/ton acid, 4 kg/t oxidant, 24 hour residence time and 60°C leach temperature, yielded elevated dissolutions between ~77% and ~96%, with a combined overall uranium recovery of ~94%. These results are not consistent with the low yields obtained at the processing plant, and suggest that the high level of uranium recovery can be attributed to the effective leaching of brannerite (most likely uraniferous brannerite and brannerite). In view of prevailing market conditions, variability tests were carried out on a representative bulk composite sample to investigate the potential to achieve similar yields under more cost-effective leaching conditions. In these tests, a single parameter was varied (e.g. acid dosage), while the remaining parameters remained at baseline conditions. The results demonstrate that uranium recoveries of ~80% can be achieved on Cooke Section ores at low acid dosages and high temperatures (18 kg/t, 60°C) or at moderate acid dosages and low temperatures (23 kg/t, 30°C). The associated reduction of input costs would represent a significant cost-saving for the Ezulwini gold and uranium recovery plant. It is concluded that the poor uranium yields encountered during commercial processing of the ore are most likely related to undiagnosed inefficiencies in the treatment plant, such as excessive acid consumption related to elevated temperatures/oxidant addition and/or insufficient leach residence times, especially when recirculating, continuous flow-through leaching systems are in use. The broader implication of this study is that uranium processing operations beyond Cooke Section may be able to optimise their process designs and reduce input costs by quantifying the different types of brannerite within their ores through automated mineralogical analyses. The present study thus demonstrates the value of a geometallurgical approach in enhancing the understanding of uranium recovery through acid leaching.

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Paton, Douglas A., David I. M. Macdonald, and John R. Underhill. "Applicability of thin or thick skinned structural models in a region of multiple inversion episodes; southern South Africa." Journal of Structural Geology 28, no. 11 (November 2006): 1933–47. http://dx.doi.org/10.1016/j.jsg.2006.07.002.

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48

Hansen, R. N. "Process network modelling of the geochemical reactions responsible for acid mine drainage emanating from the Witwatersrand tailings facilities." South African Journal of Geology 123, no. 3 (September 1, 2020): 357–68. http://dx.doi.org/10.25131/sajg.123.0024.

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ABSTRACT Acid mine drainage (AMD) and associated metal(loid) and SO42- pollution of soil, surface water and groundwater is ubiquitously associated with tailings material generated by Au mining in the Witwatersrand Basin in South Africa. The individual geochemical processes responsible for the AMD generation in this tailings material are relatively well understood. What is less clear are how these different processes interact as a network within the tailings system. Process network modelling (PNM) is a tool that can be used to study such interactive and complex networks of geochemical processes, especially when stochastic methods, e.g. Monte Carlo simulation, are included in the model development. Secondary mineral phase supersaturation requirements from classical nucleation theory are also built into the model. A PNM was developed for a tailings facility in the Witwatersrand gold basin focussing on pH, Fe(total) and SO42- concentrations in the tailings pore water and the relationship of these parameters to the dissolution of pyrite, O2 diffusion into the tailings, oxidation of Fe2+ and the precipitation of secondary minerals, specifically goethite and jarosite. The model indicated that AMD conditions develop fairly rapidly after the sulphidic material is exposed to the Earth’s oxygenated atmosphere. The concentration of H+, and hence the pH, in the tailings pore water is controlled by a number of feedbacks. The positive feedback, implying addition of H+, is the dissolution of pyrite and the precipitation of the secondary Fe3+-bearing minerals goethite and jarosite. Jarosite precipitation was shown to increase the median H+ addition rate by ~2%. The negative feedback, i.e. decrease in H+, is the oxidation of Fe2+ to Fe3+. This feedback loop produces a net excess of H+. Together with the buffer effect of goethite and jarosite precipitation, system steady-state conditions are eventually achieved with respect to pH. The pore water SO42- concentration is controlled by the positive and negative feedback of pyrite dissolution and jarosite precipitation. This feedback loop produces a large excess of SO42- and steady state conditions can only be achieved if SO42- is physically removed from the tailings system, e.g. seepage to groundwater. Oxidation of the Fe2+ produced by pyrite dissolution to Fe3+ is the only positive feedback for tailings pore water Fe3+ concentrations. The negative feedbacks are precipitation of goethite and jarosite and the oxidation of pyrite by Fe3+. The former effect is delayed as these phases first have to achieve a certain level of supersaturation in the tailings pore water solution before they can form. The precipitation of jarosite and goethite, by removing Fe3+ from solution, decreases the effect of Fe3+ pyrite oxidation causing O2 to remain the dominant oxidation mechanism. This feedback loop produces a small excess of Fe3+ over time, however, the model is very sensitive to other factors, e.g. O2 diffusion deeper into the tailings facility.

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GROVE, D., and C. HARRIS. "O- AND H-ISOTOPE STUDY OF THE CARBON LEADER REEF AT THE TAU TONA AND SAVUKA MINES (WESTERN DEEP LEVELS), SOUTH AFRICA: IMPLICATIONS FOR THE ORIGIN AND EVOLUTION OF WITWATERSRAND BASIN FLUIDS." South African Journal of Geology 113, no. 1 (March 1, 2010): 73–86. http://dx.doi.org/10.2113/gssajg.113.1-73.

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Reimer, T. O. "U-Pb Ages on Single Detrital Zircon Grains from the Witwatersrand Basin, South Africa: Constraints on the age of Sedimentation and on the Evolution of Granites Adjacent to the Basin: A Discussion." Journal of Geology 99, no. 3 (May 1991): 493–94. http://dx.doi.org/10.1086/629509.

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