The Northwest manganese mineralization comprises of supergene ores developed in a weathering crust of the Neoarchean manganiferous dolostones of the Transvaal Supergroup. These are near-surface accumulation of manganese wad and nodules. The manganese wad is preserved in a typical karstic structures on top of the weathered manganiferous dolostones within the Waterval Saprolite. The saprolite is in turn overlain with a sharp erosional contact by West-wits alluvium hosting manganese nodules. Ore formation is attributed to in-situ surficial weathering, partial dissolution and leaching of ore substances from the manganiferous dolostones. These combined processes led to the release of Mn and Fe rich colloidal particles into the overlying water column of the depository, which later precipitated as manganese nodules upon interaction with alluvial sediments which acted as substrates and centers of accretion. This study presents results on the mineralogy, geochemical constituents and geological occurrence of the ore mineralization. Mineralogical studies indicated the occurrence of romanechite, cryptomelane and galaxite as predominant manganese oxide phases, and pyrolusite and vernadite occurring in minute quantities. Geochemical and mineralogical data anomalies obtained in this study were used to develop a genetic classification of the ore deposit. On the basis of trace element geochemistry applied in this study coupled with studies of mineralogical and diagenetic features of the samples, different manganese classification schemes were adopted and inferences were made from the data interpretation which indicated supergene and hydrogenetic nature of the ore mineralization suggesting precipitation of ore substances from the weathered Mn colloids in a supergene zone.
Supergene manganese ores, mineralogy, geochemistry, ore occurrence, romanechite, General Mine, weathering crust
1. Achurra, L. E., J. P. Lacassie, J. P. Le Roux, et al. (2009) , Manganese nodules in the Miocene Bahia Inglesa Formation, north-central Chile: Petrography, geochemistry, genesis and palaeoceanographic significance, Sedimentary Geology, 217, p. 128-139, https://doi.org/10.1016/j.sedgeo.2009.03.016
2. Asikainen, C. A., S. Werle (2007) , Accretion of ferromanganese nodules that form pavement in second Connecticut lake, New Hemisphere, Proceeding of the National Academy of Science (PNAS), 104, p. 17,579-17,581, https://doi.org/10.1073/pnas.0708132104
3. Bau, M., K. Schimdt, A. Koschinsky, et al. (2014) , Discriminating between different genetic types of marine ferro-manganese crusts and nodules based on rare earth elements and yttrium, Chemical Geology, 381, p. 1-9, https://doi.org/10.1016/j.chemgeo.2014.05.004
4. Beukes, N. J., H. S. Van Niekerk, J. Gutzmer (1999) , Post-Gondwana African land surfaces and pedogenic ferromanganese deposits on the Witwatersrand at the West Wits gold mine, South African Journal of Geology, 102, p. 65-82
5. Beukes, N. J., E. W. Swindell, H. Wabo (2016) , Manganese deposits of Africa, Episodes Journal of International Geoscience (IUGS), 39, p. 285-317, https://doi.org/10.18814/epiiugs/2016/v39i2/95779
6. Burke, K., Y. Gunnell (2008) , The African erosion surface: a continental-scale synthesis of geomorphology, tectonics, and environmental change over the past 180 million years, Geological Society of America: Memoir, 201, p. 66, https://doi.org/10.1130/2008.1201
7. Colin, F., A. Beauvais, et al. (2005) , First 39Ar-40Ar geochronology of lateritic manganiferous pisolites: implications for the Palaeogene history of a West African landscape, Earth Planet Science Letter, 238, p. 172-188, https://doi.org/10.1016/j.epsl.2005.06.052
8. De Putter, T., G. Ruffet, J. Yans, F. Mees (2015) , The age of supergene manganese deposits in Katanga and its implications for the Neogene evolution of the African Great Lakes Region, Ore Geology Reviews, 71, p. 350-362, https://doi.org/10.1016/j.oregeorev.2015.06.015
9. Del Rio Salas, R., J. Ruiz, L. Ochoa-Landin, et al. (2008) , Geology, Geochemistry and Re-Os systematics of manganese deposits from the Santa Rosalia Basin and adjacent area in Baja California Sur, Mexico, International Journal for Geology, Mineralogy and Geochemistry of Mineral Deposits, 43, p. 467-482, https://doi.org/10.1007/s00126-008-0177-3
10. De Villiers, J. (1960) , The manganese deposits of the Union of South Africa: Pretoria, Geological Survey of South Africa Handbook, 2, p. 263
11. Els, B. G., W. A. van den Berg, J. J. Mayer (1995) , The Black reef Quartzite Formation in the western Transvaal: Sedimentological and economic aspects, and significance for basin evolution, Mineral Deposita, 30, p. 112-123, https://doi.org/10.1007/BF00189340
12. Eriksson, P. G., W. Altermann, O. Catuneaunu, et al. (2001) , Major influences on the evolution of the 2.67-21 Ga Transvaal Basin, Kaapval Craton, Sedimentary Geology, 141/142, p. 205-231, https://doi.org/10.1016/S0037-0738(01)00075-6
13. Frimmel, H. E. (2014) , A giant Mesoarchean crustal gold-enrichment episode: possible causes and consequences for exploration, Building exploration capability for the 21st Century, Kelley K., Golden, H. C. (Eds.), p. 209-234, Society of Economic Geologists, Special Publication 18, https://doi.org/10.5382/SP.18.10
14. Glasby, G. P. (1972) , The mineralogy of manganese nodules from a range of marine environments, Marine Geology, 13, p. 57-72, https://doi.org/10.1016/0025-3227(72)90071-0
15. Glasby, G. P. (2006) , Manganese: Predominant role of nodules and crust, Marine Geochemistry, H. D. Schulz and M. Zabel (Eds.), p. 593, Springer Science, Berlin, Heidelberg
16. Gutzmer, J., N. J. Beukes (1994) , Karst control of the Ryedale Fe-Mn deposit in the Palaeozoic Karoo Supergroup, Western Transvaal, South Africa: Berichte der Deutschen Mineralogischen Gesellschaft, Beiheft zum, European Journal of Mineralogy, 6, p. 333
17. Hem, J. (1963) , Chemical equilibria affecting the behavior of manganese in natural water, International Association of Scientific Hydrology. Bulletin, 8, no. 3, p. 30-37, https://doi.org/10.1080/02626666309493334
18. Heshmatbehzadi, K., J. Shahabpour (2010) , Metallogeny of manganese and ferromanganese ores in Baft Ophiolitic Mélange, Kerman, Iran, Australian Journal of Basic and Applied Sciences, 4, no. 2, p. 302-313
19. Lykov, Y. V., V. G. Gorelikov, B. Gantulga (2017) , Analytical research and classification of mechanism of diamond drilling-bits contact with rocks during well sinking, IOP Conference Series: Earth and Environmental Science, 87, p. 6, https://doi.org/10.1088/1755-1315/87/2/022012
20. Mero, J. L. (1962) , Ocean-floor manganese nodules, Economic Geology, 57, p. 747-767, https://doi.org/10.2113/gsecongeo.57.5.747
21. Nath, B. B., W. L. Pluger, I. Roelandts (1997) , Geochemical constraints on the hydrothermal origin of ferromanganese incrustations from the Rodriguez triple junction, Indian Ocean, Geological Society of London, Special Publication, 119, p. 199-211, https://doi.org/10.1144/GSL.SP.1997.119.01.13
22. Nicholson, K., V. K. Nayak, J. K. Nanda (1997) , Manganese ores of the Ghoriajhor-Monmunda area, Sundergarh District, Orissa, India: geochemical evidence for a mixed Mn source, Geological Society of London, Special Publication, 119, p. 117-121, https://doi.org/10.1144/GSL.SP.1997.119.01.08
23. Pack, A., J. Gutzmer, N. Beukes, H. Van Niekerk (2000) , Supergene ferromanganese wad deposits derived from Permian Karoo Strata along the late Cretaceous-mid-Tertiary African land surface, Ryedale, South Africa, Economic Geology. B, 95, p. 203-220, https://doi.org/10.2113/gsecongeo.95.1.203
24. Partridge, T. C., R. R. Maud (1987) , Geomorphic evolution of Southern Africa since Mesozoic, South African Journal of Geology, 90, p. 197-208
25. Pharoe, B. K., K. Liu (2018) , Stratigraphy of the pedogenic manganese nodules in the Carletonville area, North West Province of South Africa: A case study of the General Nice Manganese Mine, Journal of African Earth Sciences, 143, p. 79-101, https://doi.org/10.1016/j.jafrearsci.2018.03.002
26. Randall, S. M., D. M. Serman, K. V. Ragnarsdottir (1998) , An extended X-ray absorption fine structure spectroscopy investigation of cadmium sorption on cryptomelane (KMn8O16), Chemical Geology, 151, p. 95-106, https://doi.org/10.1016/S0009-2541(98)00073-4
27. Roy, S. (1992) , Environments and processes of manganese deposits, Economic Geology, 87, p. 1218-1236
28. Roy, S. (2006) , Sedimentary manganese Metallogenesis in response to the evolution of the Earth system, Earth Science Reviews, 77, p. 273-305, https://doi.org/10.1016/j.earscirev.2006.03.004
29. Sethumadhav, M. S., G. Yanni, et al. (2010) , Late Archean manganese mineralization and younger supergene manganese ores in the Anmod-Bisgod region, western Dharwar Craton, southern India: Geological characterization, palaeoenvironmental history, and geomorphological setting, Ore Geology Reviews, 38, p. 70-89, https://doi.org/10.1016/j.oregeorev.2010.06.001
30. Tinker, J., M. de Wit, J. Grotzinger (2002) , Seismic Stratigraphic Constraints on Neoarchean-Paleoproterozoic Evolution of the Western Margin of the Kaapvaal Craton, South Africa, South African Journal of Geology, 105, p. 107-134, https://doi.org/10.2113/105.2.107
31. Toth, J. R. (1980) , Deposition of submarine crusts rich in manganese and iron, Geological Society of America Bulletin, 91, p. 44-54, https://doi.org/10.1130/0016-7606(1980)91%3C44:DOSCRI%3E2.0.CO;2
32. Vafeas, N. A., L. C. Blignaut, K. S. Viljoen (2018) , New evidence for the early onset of supergene alteration along the Kalahari unconformity, South African Journal of Geology, 121, p. 157-170, https://doi.org/10.25131/sajg.121.0012
33. Vafeas, N. A., L. C. Blignaut, K. S. Viljoen (2019) , Arsenic-bearing manganese ore of the Mukulu Enrichment in the Kalahari Manganese Field, South Africa: A new discrimination scheme for Kalahari manganese ore, Ore Geology Reviews, 115, p. 1-12, https://doi.org/10.1016/j.oregeorev.2019.103146
34. Van Niekerk, H. S., N. J. Beukes, J. Gutzmer (1999a) , Post-Gondwana pedogenic ferromanganese deposits, ancient soil profiles, African land surfaces and palaeoclimate change on the Highveld of South Africa, Journal of African Earth Sciences, 29, p. 761-781, https://doi.org/10.1016/S0899-5362(99)00128-1
35. Van Niekerk, H. S., J. Gutzmer, N. J. Beukes, et al. (1999b) , An 40Ar/39Ar age of supergene K-Mn oxyhydroxides in a post-Gondwana soil profile on the Highveld of South Africa, South African Journal of Science, 85, p. 450-454
