Regolith Geochemistry and Mineralogy of the Mbalam Itabirite-Hosted Iron Ore District, South Eastern Cameroon

M. T. Nforba, V. Kamgang Kabeyene, C. E. Suh
DOI: 10.4236/ojg.2011.12003                

Abstract

Mbalam is a major emerging iron ore district in Cameroon. The regolith over the Mbalam itabirite, consists of relict, erosion and depositional units. Itabirite rock fabric is preserved in the relict regolith, the erosion unit is marked by erosion of the carapace cap regolith, with the depositional unit dominated by canga (loose fragments of hematite and/or itabirite cemented by goethite) or loose scree. Fe concentration increases from average of 46.18 wt% in the depositional soil material to as much as 79.08 wt% in the relict regolith regime with variation due to supergene weathering. Fe is the least mobile of the major elements, and the Fe oxides become significant phases and control the distributions of many elements. Absorption of P by iron oxides or oxyhydroxides appears to be the major mechanism of P retention in the different regolith environment. Au dispersion in the weathering profile occurs by two possible mechanisms (mechanical and hydromorphic) and it distribution is sporadic. Zr maintains a positive correlation with Al and Ti indicating extensive chemical weathering in the source area and resulting in a relative concentration of those residual elements. The weathered material show relatively high ΣREE; this is due to upward remobilisation from the lower primary itabirite, and the downward leaching of the upper mineralisation horizons by the descending epigenetic solutions.

Keywords

Regolith, Geochemistry, Mineralogy, Itabirite, Mbalam, Cameroon

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	C. R. M. Butt and R. E. Smith, “Characteristic of the Weathering Profile,” In: C. R. M. Butt, & H. Zeegers, Ed., Chapter III.3: Semiarid and arid terrains. Regolith Exploration Geochemistry in Tropical and Subtropical Terrains, Elsevier, Amsterdam, 1992, pp. 299-304.
[2]	C. R. M Butt and H. Zeegers, “Regolith Exploration Geochemistry in Tropical and Subtropical Terrains, (Handbook of Exploration Geochemistry,)” Elsevier, Amsterdam, Vol. 4, 1992, p. 607.
[3]	C. R. M. Butt, M. J. Lintern, and R. R. Anand, “Evolution of Regoliths and Landscapes in Deeply Weathered Terrain—Implication for Geochemical Exploration,” Ore Geology Reviews, Vol. 16, No. 3-4, 2000, pp. 167-183. doi:10.1016/S0169-1368(99)00029-3
[4]	M. A. Craig, “Regolith Mapping for Geochemical Exploration in the Yilgran Craton, Western Australia,” Geochemistry: Exploration, Environment, Analysis, Vol. 1, 2001, pp. 383-390. doi:10.1144/geochem.1.4.383
[5]	N. W. Brand, and C. R. M. Butt, “Weathering, Element Distribution and Geochemical Dispersion at Mt Keith, Western Australia: Implication for Nickel Sulphide Exploration,” Geochemistry: Exploration, Environment, Ana- lysis, Vol. 1, No. 4, 2001, pp. 391-407. doi:10.1144/geochem.1.4.391
[6]	G. Achoundong, “Vegetation,” In: N. Houstin and C. Seignobos, Ed., Atlas of Cameroon’ Les éditions Jeune Afrique, Paris, 2007, pp. 64-65.
[7]	M. Tsaléfac, “Climate,” In: N. Houstin and C. Seignobos, Ed., Atlas of Cameroon, Les éditions Jeune Afrique, Paris, 2007, pp. 62-63.
[8]	R. J. Thomas, C. Chevalier and J.F. Makanga, “Precam- brian Geology and Metallogeny of Gabon,” Journal of African Earth Science, Vol. 28, 1999, pp. 78-79.
[9]	J. P. Milesi, S. F. Toteu, Y. Deschamps, J. L. Feybesse, C. Lerouge, A. Cocherie, J. Penaye, R. Tchameni, G. Moloto-A-Kenguemba, H. A. B. Kampunzu, N. Nicol, E. Duguey, J. M. Leistel, M. Saint-Martin, F. Ralay, C. Heinry, V. Bouchot, J. C. Doumnang Mbaigane, V. Kanda Kula, F. Chene, J. Monthel, P. Boutin, and J. Cailteux, “An Overview of the Geology and Major Ore Deposits of Central Africa: Explanatory Note for the 1:4,000,000 Map ‘Geology and major ore deposits of Central Africa’,” Journal of African Earth
[10]	S. F. Toteu, W. R. Van Schmus, J. Penaye and J. B. Nyobe, “U-Pb and Sm-Nd Evidence for Eburnian and Pan-African High-Grade Metamorphism in Cratonic Rocks of Southern Cameroon,” Precambrian Research, Vol. 67, No. 3-4, 1994, pp. 321-347. doi:10.1016/0301-9268(94)90014-0
[11]	S. F. Toteu, W. R. Van Schmus, J. Penaye and A. Michard, “Preliminary U-Pb and Sm-Nd Geochronologic Data on the North-Central Cameroon: Contribution of an Archean and Paleo-Proterozoic Crust to the Edification of an Active Domain of the Pan-African Orogeny,” Acadé- mie des Sciences, Vol. 319, 1994, pp. 1519-1524.
[12]	D. Soba, A. Michard, S. F. Toteu, D. I. Norman, J. Penaye, V. Ngako, J. P. Nzenti and D. Dautel, “Donnes Geochronologiques Nouvelles (Rb/Sr, U/Pb and Sm/Nd) sur la Zone Mobile Panafricaine de l’Est-Cameroun: Age Protérozoique Supérieur de la Série de Lom,” Comptes Rendus de l'Académie des Sciences, Vol. 312, 1991, pp. 1453-1458.
[13]	V. Ngako, P. Affaton, J. M. Nnange, and T. H. Njanko, “Pan-African Tectonic Evolution in Central and Southern Cameroon: Transpression and Transtension during Sinistral Shear Movements,” Journal of African Earth Sciences, Vol. 36, No. 3, 2003, pp. 207-214. doi:10.1016/S0899-5362(03)00023-X
[14]	S. F. Toteu, J. Penaye, and Y. P. Djomani, “Geodymanic Evolution of the Pan-African Belt in Central Africa with Special Reference to Cameroon,” Canadian Journal of Earth Sciences, Vol. 41, No. 1, 2004, pp. 73-85. doi:10.1139/e03-079
[15]	E. P. Oliveira, S. F. Toteu, M. N. C. Arau′jo, M. J. Carvalho, R. S. Nascimento, J. F. Bueno, N. McNaughton and G. Basilici, “Geologic Correlation between the Neoproterozoic Sergipano Belt (NE Brazil) and the Yaounde belt (Cameroon, Africa),” Journal of African Earth sciences, Vol. 44, No. 4-5, 2006, pp. 470-478. doi:10.1016/j.jafrearsci.2005.11.014
[16]	S. F. Toteu, R. Y. Foutateu, J. Penaye, J. Tchakounte, A. C. S. Mouangue, W. R. Van Schmus, E. Deloule, and H. Stendal, “U-Pb Dating of Plutonic Rocks Involved in the Nappe Tectonic in Southern Cameroon: Consequence for the Pan-African Orogenic Evolution of the Central African Fold Belt,” Journal of African Earth Sciences, Vol. 44, No. 4-5, 2006, pp. 479-493. doi:10.1016/j.jafrearsci.2005.11.015
[17]	S. F. Toteu, J. Penaye, E. Deloule, W. R. Van Schmus, and R. Tchameni, “Diachronous Evolution of Volcano- Sedimentary Basins North of the Congo Craton: Insights from U-Pb Ion Microprobe Dating of Zircons from the Poli, Lom and Yaoundé Groups (Cameroon),” Journal of African Earth Sciences, Vol. 44, No. 4-5, 2006, pp. 428- 442. doi:10.1016/j.jafrearsci.2005.11.011
[18]	C. R. M. Butt, M. J. Lintern and R. R. Anand, “Evolution of Regoliths and Landscapes in Deeply Weathered Terrain—Implication for Geochemical Exploration,” In: A. G. Gubins, Ed., Proceedings of Exploration 97: Fourth Decennial International Conference on Mineral Exploration, 1997, pp. 323-334.
[19]	R. E. Smith, R. R. Anand and N. F. Alley, “Use and Implication of Paleoweathering Surfaces in Mineral Exploration,” In A.G. Gubins, Ed., Proceedings of Exploration 97: Fourth Decennial International Conference on Min- eral Exploration, 1997, pp. 335-346.
[20]	M. Cornelius, R. E. Smith, and A. J. Cox, “Laterite Geochemistry for Regional Exploration Surveys—A Review, and Sampling Strategies,” Geochemistry: Exploration, En- vironment, Analysis, Vol. 1, 2001, pp. 211-220. doi:10.1144/geochem.1.3.211
[21]	A. M. C. Horbe and M. L. da Costa, “Lateritic Crusts and Related Soils in the Eastern Brazilian Amazonia,” Geoderma, Vol. 126, No. 3-4, 2005, pp. 225-239. doi:10.1016/j.geoderma.2004.09.011
[22]	O. Neung-Hwan and D. D. Richter, “Elemental Translocation and Loss from Three Highly Weathered Soil- Bedrock Profiles in the Southeastern United States,” Geoderma, Vol. 126, No. 1-2, 2005, pp. 5-25. doi:10.1016/j.geoderma.2004.11.005
[23]	Jin-liang Feng, “Trace Elements in Ferromanganese Concretions, Gibbsite Spots, and the Surrounding Terra Rossa overlying Dolomite: their Mobilization, Redistri- bution and Fractionation,” Journal of Geochemical Ex- ploration, Vol. 108, No. 1, 2011, pp. 99-111. doi:10.1016/j.gexplo.2010.10.010
[24]	H. W. Nesbitt, and G. M. Young, ‘Petrogenesis of Sediments in the Absence of Chemical Weathering: Effects of Abrasion and Sorting on Bulk Composition and Miner- alogy,” Sedimentology, Vol. 43, 1996, pp. 341-358. doi:10.1046/j.1365-3091.1996.d01-12.x
[25]	H. W. Nesbitt, G. M. Young, S. M. McLennan and R. R. Keays, “Effects of Chemical Weathering and Sorting on the Petrogenesis of Siliciclastic Sediments, with Implications for Provenance Studies,” Journal of Geology, Vol. 104, No. 5, 1996, pp. 525-542. doi:10.1086/629850
[26]	B. Singh and M. Cornelius, “Geochemistry and Mineralogy of the Regolith Profile over the Aries Kimberlite Pipe, Western Australia,” Geochemistry: Exploration, Envi- ronment, Analysis, Vol. 6, No. 4, 2006, pp. 311-323. doi:10.1144/1467-7873/06-113
[27]	R. J. Bowell, E. O. Alreh, N. d’A. Laffoley, E. Hanssen, S. Abe, R. K. Yao and D. Pohl, “Geochemical Exploration for Gold in Tropical Soils—Four Contrasting Case Studies from West Africa,” Transactions of the Institution of Mining and Metallurgy, Section B: Applied Earth Science, Vol 105, 1996, pp. B12-B33.
[28]	C. A. C. Varajao, F. Colin, P. Vieillard, A. J. Melfi and D. Nahon, “Early Weathering of Palladium Gold under Lateritic Conditions, Maquine Mine, Minas Gerais, Brazil,” Applied Geochemistry, Vol. 15, No. 2,2000, pp. 245-263. doi:10.1016/S0883-2927(99)00038-4
[29]	S. A. Wilde, J. W. Valley, W. H. Peck and C. M. Graham, “Evidence from Detrital Zircons for the Existence of Continental Crust and Oceans on the Earth 4.4 Gyr ago,” Nature, Vol. 409, pp. 175-178. doi:10.1038/35051550
[30]	A. Dokuz and E. Tanyolu, “Geochemical Constraints on the Provenance, Mineral Sorting and Subaerial Weathering of lower Jurassic and Upper ssCretaceous clastic Rocks of the Eastern Pontides, Yusufeli (Artvin), NE Turkey,” Turkish Journal of Earth Science, Vol. 15, 2006, pp. 181-209.
[31]	K. Sugitani, Y. Horiuchi, M. Adachi and R. Sugisaki, “Anomalously low Al2O3/TiO2 Values for Archean Cherts from the Pilbara Block, Western Australia—Pos- sible Evidence for Extensive Chemical Weathering on the Early Earth,” Precambrian Research, Vol. 80, 1996, pp. 49-76.
[32]	T. El-Hasan, A. Al-Malabeh, and K. Komuro, “Rare Earth Elements Geochemistry of the Cambrian Shallow Marine Manganese Deposit at Wadi Dana, South Jordan,” Jordan Journal of Earth and Environmental Sciences, Vol. 1, No. 1, 2008, pp. 45-52. doi:10.1016/S0301-9268(96)00005-8